text:
Is it possible to temporarily disable UI from updating?
I think we have all been there: we add too many objects or subdivide something too many times and suddenly Blender slows down to a crawl. At the moment my system is so unresponsive that it takes minutes to cancel what I did to slow it down. This problem leads me to ask if there is a way to temporarily disable Blender from trying to update things in the UI/Viewport, so that I can tweak the settings and make it responsive again?

did you use a lot of modifiers?

Sometimes yes, it depends on the project.

if you used a lot in this project I would disable the display modifier in viewport. (the eye-icon in the modifiers)

I'm not using modifiers currently, I am using the animation nodes addon though. But I'm wondering if there is something to stop UI updates in general. Like in After Effects where you can hit caps lock to temporarily stop drawing the composition.

Animation Nodes performance tab doesn't help?

It certainly helps a little bit in this particular situation, but my question is more general. Maybe the answer is that Blender doesn't have any such functionality that would allow us to temporarily stop it from drawing updates?

In recent versions, viewport updates are not computed for Objects that:

Are disabled in Viewports in the Outliner.
Are also not required by any Viewport-enabled Objects in the depsgraph.

So to quickly make changes without waiting for viewport updates on every input, you may disable the heaviest objects in the Outliner, then select them in the Outliner.

At the time this question was asked, I believe the same behaviour could be reached by switching to an empty Layer.


text:
Editing and displaying different "layers" of vertex colors
I'm given a mesh with vertex colors that display the original material/color of an object. Now I want to classify these vertex colors according to the different materials they can be divided into.
Here is a dummy-cube for a quick example. The actual color/material:

The classification into two materials:

So, I have two different types of vertex color information associated with my object. The mesh I'm given is painted in a more complex way than the cube of course. That's why it would be very useful to see the original vertex colors while painting the vertex colors that encode the material information. Is there any way to achieve this? (like for example how layers are organized in gimp or photoshop) I did not find a satisfying solution so far. Thank's in advance for your help.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
Not all particle instances rendering
I have a tree mesh with the following structure:
• a base mesh ("tree.002") for the trunk and largest branches, with a hair particle system
• a twig mesh ("branchmesh") instanced to the above particle system, with its own hair particle system
• a leaf mesh ("leaf") instanced to the twig's system
This all seems to work out nicely in the viewport, but when I go to render,
many of my leaves are missing (though all the twigs seem to appear).
My leaves have double sided normals and both instance modifiers have "show particles when:" alive, unborn, and dead activated
Below you can see a snapshot of the render with a corresponding section of the viewport that shows just how few of my leaves are rendering.
What am I missing?

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
How to make 3D LUTs and use them in Blender?
Now that I understand a little bit more about how to work with Wide Dynamic Range  workflow , scene referred datas and OPS(ASC CDL) node, I'm asking myself how to go further and create my own 3D LUT to work with in Blender?

Given that Cegaton has dropped 500 on this, it would seem the right place to give a little more fleshing out than a typical post. What follows is a (hopefully) exhaustive and explanatory answer to the question. While it might look daunting, brevity has been sacrificed to clarity. The actual process is much simpler than it appears here, but it is hoped that the explanation that follows will help more imagers explore creative colour transformations in their work, as well as enable some to extend this well beyond 3D LUTs.
What is a LUT?
LUT is merely an acronym for Look Up Table. The term is also used colloquially to refer to a technique to apply creative looks to footage, as well as the more scientific / mathematical needs of transforming colour spaces. LUTs can be generated off of mathematical functions that are sampled at intervals, or by using tools to extract changes in images.
What is the difference between a 1D LUT and a 3D LUT?
A 1D LUT at its most basic level is a pure single input to single output transform. Transfer functions such as sRGB's OETF / EOTF and other such decodes / encodes are delivered almost exclusively via 1D LUTs. There are also multi-channel 1D LUTs, where each channel can get back a unique value based on its input, or generic single channel 1D LUTs where all channels receive the same output value given identical input values.
In the following simple single channel 1D LUT, the input value is incremented by 0.1:
# Below is a simple 1D LUT, where a single input value is
# mapped to a single output value. In the case of an RGB
# triplet, each R, G, and B value would be mapped individually
# via the lookup table.
# IN    OUT
  0.0   0.1
  0.1   0.2
  0.2   0.3
...

In the following simple 1D triple channel LUT, the single input value determines the output based on whatever channel is fed. In this case, it increments the assumed red channel by 0.1, the green channel by 0.2, and the blue channel by 0.3:
# Below is a simple 1D by 3 LUT, where a single input value is
# mapped to a single output value. In the case of an RGB
# triplet, each R, G, and B value would be looked up identically
# via the first column, but return a different value based on the
# output column.
# IN    OUT_R OUT_G OUT_B
  0.0   0.1   0.2   0.3
  0.1   0.2   0.3   0.4
  0.2   0.3   0.4   0.5
...

A 3D LUT on the other hand is a much more complex creature. Under a 3D LUT, the unique fingerprint of the three input channels forms a triplet that delivers a unique set of three values back. How is this different than a 1D single or multi-channel LUT? Given that the fingerprint of the input channels is unique, and that you receive three unique values back, a 3D LUT can be used to allow a single channel to adjust the other two channels, where 1D LUTs only change the input value given. This unique characteristic of 3D LUTs, the ability for a single channel to adjust other channels, is the reason that only a 3D LUT can adjust the saturation intents of a given image.
The following 3D LUT raises up all three channels as the green channel value reaches the peak of the cube. Here, the first three values represent the input combination, and the following three represent the output combination:
# Below is a simple 3D LUT exerpt, where a unique combination
# of three input values is mapped to a unique combination of
# three output values as a whole set. Input three values, get back
# three values. The numbers on the input side represent values that
# are scaled from zero to the cube size minus one. Being scaled in
# this fashion, care must be taken to make sure that the input values
# are properly mapped to the 0.0 to 1.0 range that the LUT operates
# on.
# IN_R IN_G IN_B OUT_R    OUT_G    OUT_B
...
  0    0    60   0.544367 0.544367 0.9375
  0    0    61   0.635998 0.635998 0.953125
  0    0    62   0.74127  0.74127  0.96875
  0    0    63   0.86195  0.86195  0.984375
  0    0    64   1        1        1
...

How large are the range of values in a LUT?
LUTs operate on an arbitrary range of values that are typically defined within the LUT format itself. In the case of a 1D LUT, it holds one line for each input and output, and as a result can be quite large. Typically 1D LUTs of 4096 values will deliver very accurate results using a simple linear interpolation assuming the “direction” of the transform is technically feasible. Some “directions” suffer breakage when the LUT resolution is not large enough to express the shape properly.
3D LUTs on the other hand, because they represent a combination of three values, are defined using what is known as a cube size. A cube size determines how many steps there are in the combinations. Cube sizes vary from older 17x17x17 cubes to more contemporary 65x65x65 cubes.
The cube size is the number of values that the range will increment before incrementing the next value in the entire series. This means that a cube size of 3 would iterate three times for each channel, until each channel went through the cycle. Note how the first three columns increment, while the following three columns represent the output values. In the case of this example, the 3D LUT is an identity LUT, which simply passes the exact same input values to output:
# Below is a simple 3D LUT exerpt, where a unique combination
# of three input values is mapped to a unique combination of
# three output values as a whole set. Input three values, get back
# three values.
# IN_R IN_G IN_B OUT_R OUT_G OUT_B
  0    0    0    0     0     0
  0    0    1    0     0     1
  0    0    2    0     0     2
  0    1    0    0     1     0
  0    1    1    0     1     1
  0    1    2    0     1     2
  0    2    0    0     2     0
  0    2    1    0     2     1
  0    2    2    0     2     2
...

This means that your final number of entries is equal to the dimensions cubed. In the case of a 65 sized cube, that would be 65^3, or 274625 entries.
If a LUT operates on a bounded range, how are the other values determined?
Given that both 1D and 3D LUTs operate on bounded ranges, interpolation, or sampling, is used to determine the quality and accuracy of the values between values. In the case of a 3D LUT, the interpolation technique can be extremely important for visual quality.
How do colour transforms factor into LUTs?
Standard 1D LUTs are commonly used to perform colour transforms along intensity, also known as transfer curves. This can take many forms such as sRGB's OETF / EOTF, REC.709's OETF / EOTF, BT.1886's viewing EOTF, one of the many logarithmic transfer curve encodings, ACES encodings, etc. A 1D LUT is well suited for such application given that many of the transfer curves are piecewise functions and no simple power law will accurately describe them.
3D LUTs require special attention given their uniquely bounded constraints. Given that a 3D LUT represents an arbitrary range, care must be taken to make sure that the range maps the range within our image. This is especially important given visual effects, motion picture, or animation work, as the data is almost exclusively scene referred. Scene referred imagery from cameras or CGI represents a very large range that is mapped to the much smaller gamut of an output device domain, extending from an extremely low value to a theoretically infinitely large value. As a result, there is no one-size-fits-all approach for 3D LUT application, and care must be taken on input and output.
3D LUTs are used in some cases to change the actual colour space primaries of a given encode. Here again, it is critical that the inputs fed to such a LUT are carefully crafted.
The bottom line is that one should never use a transform unless they are absolutely certain that the LUT in question was designed for the input imagery fed. The same caveat applies to output, as a transformed image is applicable only to a single set of output contexts.
Be aware and be careful.
How are 1D or 3D LUTs created?
How a 1D or 3D LUT is created depends on the context of usage. A 1D LUT representing a transfer function can be created using a spreadsheet or scripting language, properly formatting a function or algorithm to a specific LUT format.
3D LUTs frequently are used to take a crafted look from one series of images or a shot, and apply it equally across to other images in another series or set of shots. To achieve this, we will use a reference image that our tool will understand, apply our look to it, and calculate the 3D LUT based on the differences between the two image states.
What will you need?
To generate a 3D LUT for use in Blender, you will require:

OpenColorIO . OpenColorIO has several tools that are built when you have OpenImageIO present on your system. In particular, we will be requiring ociolutimage and ocioconvert.
Given that the original question pertains to wide dynamic range filmic LUTs, you will also require the OpenColorIO configuration package that implements them. They can be found in my answer to Cegaton's original question here. If you have arrived here and are reading this without a familiarity of the concepts, it is heavily advised you read the original question and the ridiculously long answer I gave there. With that background, you should be much more well equipped to deal with the information provided in this solution.

Can you summarize the steps involved?
Loosely, we will be doing the following steps to implement custom LUTs in Blender. Note this specifically pertains to LUTs, but a similar technique can be used to apply canned ASC CDL values in your own configuration.

We will muck creatively with a sample image and arrive at a look that we are happy with.
We will generate a unique all-in-one image that is used as our reference baseline, and plug that into our look compositing chain.
We will use OpenColorIO's tools to generate the 3D LUT from the modifications.
We will plug the newly crafted 3D LUT into our configuration and make it accessible from within Blender for reuse.

1.0 Mucking
Consider the following image. Not terribly impressive, but it has been chosen because it is a scene referred image which is a smaller region of Maxime Roz's HDRI pack. Again, scene referred imagery is a range of values that extends from zero to infinity, with no notion of black nor white, and no special meaning to values such as 1.0. Cycles, being a ray tracing engine, always generates scene referred imagery, and as such, our techniques must take this into consideration. The following attached image is of course display referred, and does not have the original scene referred values. It was created using the Filmic Blender LUT set.

After countless hours of toil and sweat, the wonderfully creative output of our grading is the following. Again, because this was generated in Blender, which as a scene referred internal model, the values extend from zero to extremely high ratios such as 50.0+ outside the window. The image attached below has been manipulated in Blender while using the views and looks present in the Filmic Blender LUT set, as above.

The work is done. Assuming we have other shots we would like to apply this look to, or build up our library of sample looks for this particular set of constraints, we need to forge ahead and craft a LUT. As we can see, there has been both a slight contrast tweak added, as well as some saturation adjustments. Knowing that only a 3D LUT can do both, we will need to create a 3D LUT for this work.
2.0 Generate the all-in-one
LUTs can be generated both via algorithm or, more commonly, from source imagery. The way to generate a look based off of a tweak one has given to source footage is to generate a known constant image and use it to compare against an identical constant, tweaked to the same tuning as the desired creative output.
There are demons hidden away here though. 3D LUTs, given that they operate on a specifically designed range of values, must be properly mapped in order to both meet the range, but to optimise their application. In this case, since the question pertains to the Filmic LUT set, we need to make sure that our 3D LUT is going to sufficiently match what we saw when we were grading the image. Some 3D LUT formats include the "shaper" compression component inside their actual LUT formats.
Given that the default Blender sRGB OETF / EOTF was never designed for any sort of creative work such as raytracing, it is sub-optimal on a number of levels. As a replacement, the Filmic LUT set consists primarily of two transformations that make work appear more photographic. First, it uses a much wider dynamic range from the scene referred values than the default sRGB EOTF uses. This means your work includes and requires light that more closely matches physical, real-world levels. As a result you'll notice much better radiosity, caustics, indirect bouncing, etc. Second, it uses a 3D LUT to desaturate the values as they ascend to the higher dynamic range, attempting to emulate what happens on colour film or DSLRs, and prevent the broken, wonky saturations that happen as colours get very intense under the default view.
When making a 3D LUT, care must be taken to match the exact same contexts that we are developing our work under. An all-in-one image covers a fully normalised range of values, at a cube size you choose. However, given that it covers a normalised range, and that our work was crafted on a scene referred range, we have to transform our all-in-one accordingly, so that the reference spaces match.
To prepare our environment, we must tell the OpenColorIO applications where our OpenColorIO configuration is. It should be noted that if we do this in the CLI and run Blender from that same CLI, Blender too will honour the location of the configuration, and ignore the internal configuration located in your installation, at datafiles/colormanagement/config.ocio.
Setting the environment variable might look like:
export OCIO=/path/to/local/configuration/config.ocio

That command looks as follows:
ociolutimage --generate --cubesize 65 --maxwidth 4225 --colorconvert "Desat Log Encoding" Linear --output /path/to/scenereferred_allinone.exr

What does it do?

--generate instructs ociolutimage that we want to create an all-in-one image.
--cubesize 65 instructs ociolutimage to use a cube size of 65, which is a very high quality 3D LUT.
--maxwidth 4225 is a somewhat optional feature to make the resulting image legible to a human. This keeps the image such that the individual cubes are small blocks of colours ascending, and is easily understandable in an imaging application. If we leave this out, the values end up unaligned and can be tricky to understand in an image viewer.
--colorconvert "Desat Log Encoding" Linear instructs ociolutimage to transform the all-in-one for us, from the normalized range which we interpret here as the "Desat Log Encoding" transform, to the scene referred "Linear" encoding we are feeding in our reference space. This will transform the values from 0.0 to 1.0 to the scene referred range of the desaturation shaper, which extends up to 184.32 scene referred. This is also why we need to specify our OCIO configuration above. It should point to the Filmic LUT set.
--output /path/to/logencoded_allinone.exr specifies where we want the output EXR file to be stored on our drive.

Using the above output file scenereferred_allinone.exr, we simply add it into our node chain right where our source enters. In the viewer, we can use the Save Image As... function to save the adjusted all-in-one as a modified version EXR. Save this file as ````scenereferred_modified.exr``` at 32 bit depth.
3.0 Generate the 3D LUT
Now we have a modified all-in-one that is precisely identical to the modifications in our original grading node chain. We will use this as the blueprint to create the 3D LUT.
First we must be certain that we establish the OCIO environment variable so the following transforms are understood:
export OCIO=/path/to/local/configuration/config.ocio

Next, we have a quick hop to return the image from the scene referred domain that it currently exists in, to the log-encoded nonlinear range that the transforms in the Filmic LUT set expect. Why? Because if simply scale our cube size, our 3D LUT would be biased to a range that isn't terribly perceptually uniform. This would potentially lead to posterization or poor quality. To make our 3D LUT useful, we need the reduced range to reference a more perceptually uniform set of values with our modifications.
That transform looks like this:
ocioconvert scenereferred_modified.exr Linear logencoded_modified.exr "Desat Log Encoding"

The above transforms our all-in-one image into the log encoded range our LUT set expects. Both "Linear" and "Desat Log Encoding" are transforms listed in the Filmic LUT set, and again why we have to specify the environment variable above.
Now that we have the EXR file primed for generation with our modifications, we will again lean on ociolutimage to do the heavy lifting.
ociolutimage --extract --cubesize 65 --maxwidth 4225 --input /path/to/logencoded_modified.exr --output /path/to/3dLUTdemo-LUT.spi3d

Breaking this down:

--extract instructs ociolutimage to extract the 3D LUT from the input file, which is assumed to be an all-in-one created with the options provided.
--cubesize 65 instructs ociolutimage that the image contains a cube size of 65. If we leave this out, ociolutimage will complain that the file doesn't match the default expectation.
--maxwidth 4225 instructs ociolutimage that the image is of the specified width. If we leave this out, ociolutimage will complain that the file doesn't match the default expectation.
--input /path/to/logencoded_modified.exr simply specifies the path to our input all-in-one modified image. Remember, it should be perceptually uniform if you want your 3D LUT to not look whack.
--output /path/to/3dLUTdemo-LUT.spi3d is the path to the solution to the question; the 3D LUT, in Sony Pictures Imageworks format.

4.0 Integrate the thing
As for the final step, we will be using the look section of the Filmic LUT set, and adding in our own. This again will require a few extra entries because of the slightly complex method that the views and looks are implemented to generate the desaturation.
First, make a backup copy of your Filmic LUT set just in case you mangle something up beyond recognition.
Next, copy the 3dLUTdemo-LUT.spi3d into the looks directory of the Filmic LUT set.
Now, find the config.ocio file for the set at the root of the directory and open it with a standard text editor. We are going to do the following:

Add a new desaturation log encoding base view to base our looks off of.
Add our new look to the list of looks.

To accomplish the first thing, we need to simply enable the preexisting transform for the "Desat Log Encoding" into a view. To do that, locate the section that looks like the following:
[...]
displays:
  Filmlike:
    - !<View> {name: sRGB EOTF, colorspace: sRGB EOTF}
    - !<View> {name: Data, colorspace: Raw}
    - !<View> {name: Scene Linear, colorspace: Linear}
    - !<View> {name: Filmic Log Encoding Base, colorspace: Filmic Log Encoding}
    - !<View> {name: Filmic High Contrast, colorspace: Filmic Log Encoding, look: +High Contrast}
    - !<View> {name: Filmic Medium High Contrast, colorspace: Filmic Log Encoding, look: +Medium High Contrast}
    - !<View> {name: Filmic Medium Low Contrast, colorspace: Filmic Log Encoding, look: +Medium Low Contrast}
    - !<View> {name: Filmic Low Contrast, colorspace: Filmic Log Encoding, look: +Low Contrast}
    - !<View> {name: Filmic Base Contrast, colorspace: Filmic Log Encoding, look: +Base Contrast}
#    - !<View> {name: Debug, colorspace: Debug}
[...]

We add the preexisting transform to the list of views as follows. We will tuck it in just after the Filmic Log Encoding Base. Again, the reasons for this additional step is the way in which the desaturation is crafted for the transform set, and therefore we require a very specific view for our LUTs:
[...]
displays:
  Filmlike:
    - !<View> {name: sRGB EOTF, colorspace: sRGB EOTF}
    - !<View> {name: Data, colorspace: Raw}
    - !<View> {name: Scene Linear, colorspace: Linear}
    - !<View> {name: Filmic Log Encoding Base, colorspace: Filmic Log Encoding}
    - !<View> {name: Desat Log Encoding Base, colorspace: Desat Log Encoding}
    - !<View> {name: Filmic High Contrast, colorspace: Filmic Log Encoding, look: +High Contrast}
    - !<View> {name: Filmic Medium High Contrast, colorspace: Filmic Log Encoding, look: +Medium High Contrast}
    - !<View> {name: Filmic Medium Low Contrast, colorspace: Filmic Log Encoding, look: +Medium Low Contrast}
    - !<View> {name: Filmic Low Contrast, colorspace: Filmic Log Encoding, look: +Low Contrast}
    - !<View> {name: Filmic Base Contrast, colorspace: Filmic Log Encoding, look: +Base Contrast}
#    - !<View> {name: Debug, colorspace: Debug}
[...]

Finally, we add the look itself down near the bottom of the file. Looks are added in a first in, last listed fashion. We can add the look to the top of the looks section as follows:
[...]
looks:
  - !<Look>
    name: My Demo Look
    process_space: Desat Log Encoding
    transform: !<GroupTransform>
      children:
        - !<FileTransform> {src: 3dLUTdemo-LUT.spi3d, interpolation: best}
        - !<FileTransform> {src: Base_DesatCrosstalk_DesatLog.spi3d, interpolation: best}
        - !<FileTransform> {src: DesatLog_to_EncodeLog.spi1d, interpolation: best, direction: inverse}
        - !<FileTransform> {src: Linear_to_0-7_1-05_Tonemap.spi1d, interpolation: best}

  - !<Look>
    name: Greyscale
    process_space: Filmic Log Encoding
    transform: !<MatrixTransform> {matrix: [0.2126729, 0.7151521, 0.0721750, 0, 0.2126729, 0.7151521, 0.0721750, 0, 0.2126729, 0.7151521, 0.0721750, 0, 0, 0, 0, 1]}

  - !<Look>
    name: False Colour
    process_space: Filmic Log Encoding
    transform: !<FileTransform> {src: Filmic_False_Colour.spi3d, interpolation: best}
[...]

Note that there are four transforms listed in our witch's brew. Why? In order:

- !<FileTransform> {src: 3dLUTdemo-LUT.spi3d, interpolation: best} is our LUT that we created. The process space takes care of taking us to the "Desat Log Encoding" range of values, and the 3D LUT applies our creative transform to those values.
- !<FileTransform> {src: Base_DesatCrosstalk_DesatLog.spi3d, interpolation: best} is the basic desaturation for the Filmic Set. This is required to match the desaturation look when we were generating the grade.
- !<FileTransform> {src: DesatLog_to_EncodeLog.spi1d, interpolation: best, direction: inverse} is the reduced range from the desaturation range shaper. This stores the encoded image with a display referred white that is lower than the desaturation range. The reasons for this are beyond the scope of this document.
- !<FileTransform> {src: Linear_to_0-7_1-05_Tonemap.spi1d, interpolation: best} applies the "Base Contrast" tonemap look to the reduced range, as they were designed. This final transform should match the tonemap transform you graded under, if you happened to have. If you didn't, you can leave this out. Pay attention to you views and looks when grading, as you must match the chain perfectly in order to get 1:1.

Test it out
If all went well, you can now load Blender and find your newly created My Demo Look listed in your looks. To apply it to any scene referred EXR that you have lit / modified under the Filmic Set, you now must use the newly created Desat Log Encoding Base view we created, with our My Demo Look. It will be a 1:1 match with your original grade, now nicely canned way for application against other shots or used as a base entry point.
The adventurous types can further their efforts by exploring canning ASC-CDL values into pre-baked looks, using the OCIO environment variables to set up grading sessions based on shot names and numbers, or other such powerful tricks. If anyone is interested in these sorts of drek and the further applications listed, feel free to ask them as a question. This will keep already lengthy solutions from sprawling out of control, as this one already has.
Hope this helps...

Check out 2.79 test build, is 3D LUT now part of the official distribution? Or am I just seeing things.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Lofting: can I copy a Shape-Keyed mesh for each frame of its animation?

I have made a simple profile mesh (an edge loop) which I've animated along a path
using 'Follow Path'.
It has a number of Shape Keys, and as it moves along the path,
it changes shape.
I would like to capture a copy of the full state of the mesh, in place, at each
frame of its animation.

This would be, if you like, a sort of 'physical onion skinning'. Dupliframes capture the transformations of the mesh at each frame, including tilts and scales derived from the path,  varying those along the path, so come very close. But they don't capture the Shape Keys. If I alter the shape, it changes in all the duplicates,irrespective of keyed frames.
I'm attempting this in the hope of modeling with the resulting copies: creating a mechanism for lofting between varying profiles along a curve with a reasonable degree of accuracy, and ease of workflow.. so if there's an alternative route to that, please comment.

Think I have something similar  re this question  A follow path constraint gives an easy way to put shape at either end, and fill in the "ribs".  Be simple enough to convert from offsets to frames .Could you provide a small sample file?

Bmesh script
Select the profile mesh, run script. Creates a copy for each frame from scene frame start to scene frame end.

A simple edge loop animated with follow path constraint, scale, and a mix of two shape keys.  BMesh.from_object gives a mesh snapshot at that frame (Apologies for low quality gif)
import bpy
import bmesh
from mathutils import Vector, Matrix
from math import radians, degrees
context = bpy.context

dg = context.evaluated_depsgraph_get()
scene = context.scene
ob = context.object
me = ob.data
bm = bmesh.new()
f = scene.frame_start
step = 1
while f <= scene.frame_end:
    scene.frame_set(f)
    bm.from_object(ob, dg)
    rme = bpy.data.meshes.new("Rib")
    bm.to_mesh(rme)

    copy = bpy.data.objects.new("Rib", rme)
    copy.matrix_world = ob.matrix_world
    scene.objects.link(copy)
    bm.clear()  # interesting without.
    f += step

Skinning the thing.
Rather than having an object per rib, could also make one object.  Taking advantage of the order each rib ring is added, can bridge these edgeloops with bmesh.ops.bridge_loops  Could be done on a lower level by creating faces.

import bpy
import bmesh
from mathutils import Vector, Matrix
from math import radians, degrees
context = bpy.context

dg = context.evaluated_depsgraph_get()
scene = context.scene
coll = context.collection
ob = context.object
mw = ob.matrix_world.copy()
me = ob.data
nverts = len(me.vertices)
nedges = len(me.edges)
bm = bmesh.new()
f = scene.frame_start
step = 1
rings = []
while f <= scene.frame_end:
    scene.frame_set(f)
    bm.from_object(ob, dg)
    bmesh.ops.transform(bm, verts=bm.verts[-nverts:], matrix=ob.matrix_world)

    rings.append(bm.edges[-nedges:])
    f += step

# build from rings
next = rings.pop()
while rings:
    ring = rings.pop()
    bmesh.ops.bridge_loops(bm, edges=ring + next)
    next = ring

rme = bpy.data.meshes.new("Rib")
bm.to_mesh(rme)
copy = bpy.data.objects.new("Rib", rme)
#copy.matrix_world = mw
coll.objects.link(copy)

That works very nicely ...You're ahead of me!.. I was going to explore the API and try out  my inexperienced Python  to attempt just what you've done in your edit. It would have taken me a long time.  There'll be plenty more to play with :)

@RobinBetts Using what is prob a better fill method here

just can say: impressive!!! - i wish i would understand what the code does... :(


text:
Proportional Editing - Limit to selected?
This seems an obviously desirable option for proportional editing: to be able to transform only selected elements, using, say, the active element as the center of falloff. Is there a Blender way to achieve this reasonably quickly?
I know it can be done by hiding the elements you wish to remain untransformed, but often you want to see them during the transformation.

nope. proportional editing works by affecting the surrounding unselected vertices.

I wonder whether there are any major obstructions to scripting this, apart from my lack of expertise. I imagine you could use vertex weights?

In Object Mode, simply lock the transforms of the objects you don't want to be affected : in the Properties pannel (T), clic the locks next to the Location/Rotation/Scale properties.
In Edit mode, I don't think it's possible.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Large values (Inf) in raw depth map
I render depth maps, in Cycles, in OpenEXR format (because I need the actual distances) and later read them in python using the openexr package.
I save the depth maps like this: Connect 'Depth' of RenderLayers node to 'FileOutput' node for which in turn I set output format to 32-bit OpenEXR and enable 'Zbuf'.
For some of the scenes (not all) I have, I notice that the depth maps have large values like Inf or 1e10.  Normally, should the value get clipped to the distance of the far plane?  How do I correct for this?


text:
Z buffer read from exr file is all ones
I render RGB images and their depth maps as well for a series of frames (using cycles).  Specifically, I need not a B/W depth png/jpg image, rather the actual depth values itself, which I can later read off in python.  I found the exr to be the oft suggested format in online forums, as I want to store float values as such.
So, I stored the rgb image as well as the z buffer together in a .exr file.  In python, while I could reassemble the rgb image perfectly, I discovered the Z channel info to be a matrix of ones.  It should actually contain the float depth values.
What could be going wrong here? I have checked the 'zbuf' option in output properties.
For reference, this is the code I use to separate rgb and z values from the exr file:
import sys
import numpy as np
import OpenEXR as exr
import Imath

def readEXR(filename):
    """Read color + depth data from EXR image file.

    Parameters
    ----------
    filename : str
        File path.

    Returns
    -------
    img : RGB or RGBA image in float32 format. Each color channel
          lies within the interval [0, 1].
          Color conversion from linear RGB to standard RGB is performed
          internally. See https://en.wikipedia.org/wiki/SRGB#The_forward_transformation_(CIE_XYZ_to_sRGB)
          for more information.

    Z : Depth buffer in float32 format or None if the EXR file has no Z channel.
    """
    print(filename)
    filename = str(filename)
    exrfile = exr.InputFile(filename)
    header = exrfile.header()

    dw = header['dataWindow']
    isize = (dw.max.y - dw.min.y + 1, dw.max.x - dw.min.x + 1)

    channelData = dict()

    # convert all channels in the image to numpy arrays
    for c in header['channels']:
        C = exrfile.channel(c, Imath.PixelType(Imath.PixelType.FLOAT))
        C = np.fromstring(C, dtype=np.float32)
        C = np.reshape(C, isize)

        channelData[c] = C

    colorChannels = ['R', 'G', 'B', 'A'] if 'A' in header['channels'] else ['R', 'G', 'B']
    img = np.concatenate([channelData[c][...,np.newaxis] for c in colorChannels], axis=2)

    # linear to standard RGB
    img[..., :3] = np.where(img[..., :3] <= 0.0031308,
                            12.92 * img[..., :3],
                            1.055 * np.power(img[..., :3], 1 / 2.4) - 0.055)

    # sanitize image to be in range [0, 1]
    img = np.where(img < 0.0, 0.0, np.where(img > 1.0, 1, img))

    Z = None if 'Z' not in header['channels'] else channelData['Z']

    return img, Z

def main(fpth):
    img, depth = readEXR(fpth[-1])
    print(np.max(depth))
    print(np.min(depth))

    return

if __name__ == '__main__':

    main(sys.argv[1:])

been looking into this and the only way I could export the Z channel was to use the compositor and link image, alpha and depth to the output node before rendering and saving the exr file

If you look at the edit, you can see the nodes.  This was what I was using.  Acc to your suggestion, should I connect Image to composite node as well as the output node?

Make that file output node use openEXR as format, so that you get the depth data in a linear scale.

what i meant is plugging everything from render layer to composite node (no other nodes) was the only way i got an exr which, when opened with blender and passing depth through normalise node, actually gave me a z pass i could visualise. it also showed up in exrdisplay but looked like just 1s and 0s, nothing in between

Connecting both Image and depth to composite node worked!  To read the Z values, the python code mentioned in the OP changes slightly, with that info being under the channel name 'Renderlayers.Z" or something like that. Maybe you should post this as an answer. Thanks a lot! Sry for the late reply, been having some internet issues.

Actually whilst writing my answer I worked out why it didn't work in the first place :)

You just need to disable the compositor in Output Properties > Post Processing > Pipeline > Compositing. Basically if compositing is enabled only the Image pass gets forwarded to the composite node (even if Nodes weren't enabled) and the Depth defaults to Z=1.000

If you do need to use the compositor, make sure you also link Depth to the composite node to get an exr file with a correct Z channel:


text:
Colourful artifacts fly past my camera and I don`t why
I have been trying to create a ghost pianist animation in blender. Everything works perfectly fine, but then when I play my render, glowing artifacts fly past my camera. But when take a look at my animation in the viewport those flashing things or artifacts are not seen. They only appear in the render.

I have added a cube for the dust with a principled volume shader, I thought that might be the problem. So I removed the dust but the problem still persists.
The Blend file:

if you need more details or the project file just ask

please provide blend file. open https://blend-exchange.com/ and follow instructions.

                              the project file

thank you. Can you please do "File"-> "external data" -> pack resources then save your blend file and upload again?

@chris i have packed the resources and everything but when I upload the file with the link you provided it says that the file could not be more than 30MB but my file is 60MB

I just rendered this at 50% after replacing the missing textures on the piano, and I'm not seeing the artifacts.  This makes me curious as to which version of blender you're using.  I rendered with 2.93.1.  Perhaps they're an artifact of you rendering at 70%?

@marty Fouts      I rendered my project using blender v2.93.0

Perhaps they're an artifact of you rendering at 70%? i am not sure

I've just rendered the project using v2.93.1 at 100%, after correcting the resolution from 980 to 1080 to match 1080p, and I can't find any artifacts.  sorry.

thank you so much for your suggestions marty fouts and sorry for the late reply


text:
How to make a material that toggles between 2 colors when object surface overlapping?
I want to make a material that toggles between 2 colors when overlapping.
For example: if the object surface overlaps an odd number from the camera ray, the material will show yellow. If the object surfaces overlap an even number from the camera ray, the material will show cyan. If it's not possible, using a compositor is fine too.

This is a video example I want to achieve. (3:20 - 3:33)
https://youtu.be/zkLJoFp2UAE?t=200

I'm pretty sure your example will have been done in compositing.. that leaves much more room for flexibility; you can shoot your basic plates, and then decide how to combine them at a later stage.
But if your shapes are single surfaces, and you don't mind using OSL, which means you can't use your GPU,then this could be enough for a variety of effects:
shader LayersBehind(

 // Number of layers found behind P
 output int LayersBehind = 0
)
{
    point ray0 = P;     //The first of a sequence of ray origins
    int limit = 20;     //Limit on length of ray-chain

    while ((LayersBehind<limit) && trace(ray0,-I,"mindist",0.000001)){
        getmessage("trace", "P", ray0);
        LayersBehind++;
    }
}

The output of this script-node is the number of surfaces hit, behind the shading-point, on the way out from the camera.

I guess the computation for this kind of render isn't too high, so sacrificing your GPU may not be too much of a hit.


text:
Texture looks fine in Rendered 3D View, but gets "Striped" when I try to bake it
I'm pretty new in Blender. Created simple model, unwrapped it, then found some free textures in the Internet, and applied them to my object, mostly using either Object or UV coordinates for this. After that object looks fine in 3D Rendered view, but when I try to bake it to get single Texture file to be able to export model to game later - somewhy some of textures got "striped", looking like having odd scale or projection.
This happens not every time I try to bake it - it baked fine once, but then I've changed UV Map a bit and tried again - it looks goofed up again. What am I doing wrong?


text:
How to turn off moving objects without gizmo or shortcut?
Can I turn off moving objects/vert etc. when clicked and dragged on empty space?
I want to be able to use only gizmo or shortcut, to prevent me from moving my stuff accidentally.
I know I can change threshold, but I'd like to remove it for good.

You can do so by disable the Move Tweak Keymap in the Preferences.


text:
Animation attaching a string to a balloon
So I have two objects... a UV sphere and a rope that I modeled. All I want to do is have two different cloth physics (one for sphere, one for rope) and basically attach the sphere to the rope. The whole idea is to have the sphere raising up and dragging the rope with it.
Could someone kindly explain how I attach two objects with two different cloth physics please? I'm struggling a bit.
Thank you!

Related https://blender.stackexchange.com/questions/629/how-to-simulate-string

I did follow the balloon simulation link above using the copy location constraint.. but objects just  seperate.

@MattB If you followed the instruction in the attached Balloon sim answer and it was still separating then most likely one of your vertex groups or the soft body goal vertex group is wrong or the constraint not correctly configured.  Go through the process again or download the sample blend file and compare that with your setup. Failing all that, post images of your constraints, soft body settings, vertex groups, etc. and if possible an animated gif of your results.


text:
How do you create a curved sequence of vertices?
I am trying to get the vertex that is highlighted and the two on it's left side and right side to be curved as seen with many of the ones done on the left. I have been manually doing it but I feel as though there should be an easier way to make more perfect curves.

I have tried using a bezel but when doing so it doesn't ever do anything.
I was also tried creating a path and then joining the two objects but that gave me the error "no mesh data to join"
How would I go about accomplishing this?

How about using actual Bezier Curve objects, if you want to draw curves? You mention using but then proceed to link to an unrelated video of beveling

Sorry, I had a bunch of tabs open on different things that I was trying and I meant to type bezel but I typed Bezier Curve because when I swapped tabs to doublecheck I was using the right word I went to the wrong tab.

If using bezier curve, make sure to choose the correct spline type to start. You can block out the main start and end points of a curve with poly handle, and then switch to bezier to then stretch and arc your curves to match the shape you want.

Since you are using a mesh object, select the single vertex and use Ctrl + B to start the bevel, and in the Operator Panel (F6 for popup) tick the option 'Vertex Only' and then increase the number of Segments to get a nice curve.
Here I have completed this process on a simple plane with the face deleted so as to imitate your scenario.

After, you can turn on Proportional Edit with 'O' and use the MMB to increase/decrease influence and move the vertices around to shape them.

Thank you! This will do quite well! Also for the record, the face is not deleted, I had it in wireframe because I have a background image I was somewhat following. I just hid it for the image as to not make things messy.

Didn't know that I could do that. That would for sure save a lot of time for some of the ones I do. What I had here was just a rough sketch of the idea and was polishing it up here but I have done some exact tracing by hand before and knowing this would for sure save me some time. I'll try it out next time I trace something exactly.

Depending on the image  on auto trace - if the image is a solid color and you can get the corners as sharp as you need, then that might be okay, but my experience is that auto trace has a tendency to be inaccurate and noisy as far as curve points go. Some of us prefer the way blender curves handle compared to vector editors.


text:
Problems with shading on curved surface
I'm having some problems with the shading on a curved surface on my model, in with the studio light with lines you can clearly see how the shading goes weird around the bend, I can't figure out how to fix it. Thanks in advance! :D
First image is the flat shaded version, second is using the built in studio MatCap, third is UV
Edit: Picture of UV added

Well If you are using UV for mapping that texture, it means your UV is not connected in those edges at all and for even worse, each island is with a different scale... Did you apply scale? How did you unwrap it? There are multiple questions, solution,s and possibilities, please clarify your situation more. show us some UV or share file with us

is it a problem of shading or a problem of UV?

I think this is one of the default builtin environment maps under the solid shading mode, created precisely for diagnosing shading and normals, since any slight discontinuity will be highly visible

I updated the pictures with description, had forgotten that... as well as added uv, the white with lines is using the build in studio MatCap. :)

The check horizontal and check vertical matcaps are supposed to make objects look weird like that, in order to highlight deviation from horizontal or vertical.  Your object deviates where it should.
If you think your object looks weird try some of the default objects.  Here's a UV sphere:

Your object has good topology and reasonable UV maps.  It looks fine using, say, the metal carpaint Studiolight

Ah! Thanks, need to read up on these! Now I have one less thing to worry about!


text:
Ocean modifier value cant be keyframed
I'm trying to animate the ocean modifier and I really want to use the direction value. For some reason It does not seem like it can be keyframed, is there any way to keyframe the value or a workaround? Using 2.81

you can use drivers for any slider you have just make an empty and assign a driver for the slider to the empty position. here is a quick tut: https://youtu.be/5SdKAUsjcsg

@Mobin This property specifically can't be animated, I don't think it is possible to unless you are willing to dive into blender's source code and change the property definition. But anyway I think they set it as non-animatable for a reason so you won't be able to unfortunately.

Damn, this is probably the best way I've found to loop the ocean modifier


text:
Color with falloff | Animation nodes 2.1 in blender 2.81a

I have these squares that spin 90 degrees when the falloff passes over them, I want them to change color from blue to magenta at the same time, I've made this array to clone one and got the color to work but it's only effecting the first one since they are all using the same material. How do I do this?
I either want to color the emission node using the falloff
OR
Change color along with the 90 degrees of rotation
Rendered in cycles
I would love some help with this! :)

Use the Object Color Output node which allows setting viewport color per object.

How would I implement that?

You can make use of the "Viewport Color" property of each object, since this property can be accessed in any shader.
See my answer here for more information : https://blender.stackexchange.com/a/163699/86891
In your animation node tree, you need to add an "Object Attribute Output" set to "color" :

Edit :
As of V 2.1.7, thanks to 3DSinghVFX there is a node specifically for this : The object color output.

Then access it in your shader :

These two objects share the same shader, but I am modifying the left one's color in my animation nodes tree :

In order to change each individual object's color, use this setup :

Don't forget to tweak the "Evaluate Fallof" node to output a list instead of just one value. You need to click on the button on the right of the "location" field in this node. Notice how it is blue tinted.
Result :

Okay, but how could I connect that to a falloff for example? I want everything inside the falloff to be one color and outside, another. Thanks for the help! :)

Super thanks! one step closer! I think I've missed something due to it still only reacting with the first copy, what have I missed? https://imgur.com/a/RkIzQK4

https://imgur.com/a/urh8Qau higher quality of the nodes

@TECHGUNK Yeah, this isnt super obvious ! You need to tweak the "Evaluate Fallof" node to output a list instead of just one value. You just need to click on the button on the right of the "location" field in this node. Notice in my screenshot it is blue tinted. After that you can get rid of the "create float list" node since it is superflous

also don't forget to link your object's positions in the evaluate fallof node else it will be evaluated will the default 0,0,0 position

You node god! Working perfectly now! Thank you! :D

@TECHGUNK Great !! Happy to have helped you


text:
Sharp Shadows Problem
I'm fiddling about with a model from Bayonetta 2, learning how to do textures and junk, but when I look at her nose I noticed some ugly bad sadness.

How do I smoothen the shadow out? I haven't noticed this elsewhere on the model. Also, I was having a similar problem on a model I was making from the ground up but for some reason felt compelled to ask about it now.
EDIT: just noticed the same problem on her jaw.
ANSWER: Instead of flipping the normals or whatever, press W in edit mode and press "smooth". It's right underneath the flip normals option.

Double check the normals of the problematic faces, they might be inverted.

Thank you for the response, but I flipped the normals several times to no avail. However, I noticed a "smooth" option right underneath "flip normals" after pressing W in edit mode. It fixed the strange shadows.

Great. Please right your own answer. That'll help the next inquirer!


text:
Can`t get my raindrops to make a splash on the floor
For the past couple of days, I have been breaking my head to solve this issue.The problem is that whenever a raindrop in my scene falls to the ground it doesn`t make a splash(the raindrops are emitted from the plane at the top)

So basically I made the splash by using planes with the texture of an image of a splash like this and put them into a collection by pressing 'ctrl+G'

Then I added a particle system to the plane on which the raindrops falls. I used the hair particle type, not the emitter.

And I made the object to render as a collection and then I chose the instance collection as the collection of the 'splash' planes.

Next, I added a new texture>went to the texture properties tab>added all the images of the wet map I created using Dynamic print physics(this makes the raindrops leave a white mark on the floor and then fade away after some time).

Something like this

Then I checked the 'cyclic' and 'Auto-refresh' options,changed the mapping coordinated to UV,selected the map and under the influence I selected the 'density' option instead of 'general time'

And when I play the animation the planes with the splash texture stays stationary throughout the whole animation.
The link to the tutorial I am following in youtube
Download the blend file over here
Update

Comments are not for extended discussion; this conversation has been moved to chat.

There are some known old bugs in the particle system and this seems to be one of them. The distribution of (hair) particles with image textures is kinda bugged.
When you use an Image Sequence to distribute the particles it looks like Blender uses only the current image at the current frame only at the moment when the particle settings are updated to calculate the possible spots for the particles. This calculation is not updated when the animation runs.
For the rain example here this means, when you're at frame 1 there are no particles hitting the road and the density texture is empty (=black). In consequence, you will see no splashes for the whole animation because Blender used the first empty image for the whole animation to calculate possible spots for the particles and never updated it.
On the other hand, when you're for example at frame 130 and update the particle system by changing something then Blender uses the 130th image of the sequence to distribute the splashes. This image has some white dots on it and is used for the whole animation. In consequence, you will see only around frame 130+ a few splashes because here the images have some white spots (=density weight for the particles).
The bug also causes to freeze the particle splashes now and then during the whole animation.
The mowing/shaving animation I made a while ago worked because it starts with a full density image. At least as long you're at frame 1 when you change things. The problems then occur at higher frames.
How to Fix the Animation with the Bug?
Knowing this is quite simple to prevent the bug.

in the timeline go to a frame where you have a full density map = a white image = "frame X". If there is no such a frame (like in this rain example here) then just paint the first image completely white and go to frame 1 (="frame X"). For the final animation, you will drop this dummy frame, of course.
make sure you have enough particles. It looks like Blender distributes them all at the moment of the update and then filters them with help of the images sequence when the animation runs. Even if there are only 500 filtered particles visible at a given time you need all e.g. 50000 at the beginning of the calculation.
update the particle physics by disabling and enabling it immediately again in the viewport by clicking the "eye" icon
if you need to change the particle system repeat these steps to initialize it properly

Example: Preparation for the particle update
Go to frame 1 at the timeline. Make sure there are 50,000 particles and image 1 is painted completely white. Then disable and enable the particle system in the viewport to see all particles at the same time. This state Blender will use to filter/manipulate the particles with help of the image sequence.

Example: Testing the animation
The setting Texture Settings > Influence has [X] Density and [X] Hair Length enabled. Run the animation. Here is frame 47 of the animation, the particles are visible and animated :-)

Wet Road on a Rainy Day Animation
First, the particles are selected to see the planes. Then they are unselected to see the final animation:

Thank you so much but it still isn`t working for me :( I think I am doing something wrong. I have updated the current status of my project after following your method.Could you share your file that you modified  so I can correct my project

Oh darn! Here is the file: https://drive.google.com/file/d/1A3KnTt0BoJeWFUa-TSXOr0Lnhu9Pfqjx/view?usp=sharing The images are not included because it's 900 MB. Try File > External Data > Find Missing Files to fix the path. Hope that helps!

great!thanks so much

@Blunder ... Holly goodness !!! All those years of pain just for a "white frame" ??? It hurts even more now :) Thanks for such discovery. I'm going to test with Vertex Weight ...


text:
Final rendered animation is really wierd
My rendered animation is turning up really weird. I don`t even know how to explain the issue. The animation isn't smooth and it's glitchy...I guess.
I have turned up the resolution, changed the samples, removed the depth of field etc. And none of them helped. I am using cycles render.
Here`s a small clip of my render (for your understanding and shared via Google Drive)
https://drive.google.com/file/d/1edwqi_gWVIZnjhxYG0VQb5z-F0PEU0Q_/view?usp=sharing

It seems to be a denoise problem. The default denoise options currently offered in blender (AI, Optix and the original blender denoiser) produce jittering because they do only Spatial Denoising, meaning that they use only one frame for input, so all images are denoised separately. The main problem with this approach is that noise patterns might not be consistent or homogeneous from one frame to the next. Sometimes this kind of denoising might actually create more problems than using no denoising at all.
I wrote nice answer about video denoising software that you can use:
Denoising Animations in Cycles
You can also use a build in animation denoiser, but it only avaliable via comand line:
How to denoise animations using Blender's Temporal Denoiser?

Seems like denoising issues with not enough samples. Increasing sample amount should help.

It actually doesn't help unfortunately :(


text:
What is the most easiest way to make a simple sponge in blender?
What is the easiest way to make a photo-realistic sponge? I am just asking this question out of curiosity and boredom. I know the modelling is really easy and I got that covered but the shading is kind of confusing and I am not really sure how to make the shading for a sponge. So I have a simple question in my mind, how do you make a cool simple sponge in blender with a very simple but photorealistic shading?
I want a simple answer!!
Something like this

Here is my proposition: A mix of 2 Noise Texture and one Voronoi nodes, one with small orange dots on a yellow background, another one with a little bit bigger white dots, and at last the big orange holes. I use the same mix for a Bump node. I put the Specular at 0 and the Roughness at 1. I also give it a bit of Subsurface. For real holes, or aven if you want a bit of relief on the edges, you could use a Displace modifier (with Voronoi texture) or sculpt some holes:

Hummm grainy cheese

@ Duarte Farrajota Ramos, I would say cheesy sponge


text:
Remove object from multiple vertex groups
Blender assigned automatic weights to my object in a weird way and now many bones seem to be moving an object. Is there an easy way to first remove the object from every vertex group before then assigning it to the correct one?

Take the object into edit mode and click on the little "vertex group specials" ˅ that is below the plus and minus symbols in the vertex group panel. There you can find the option to remove the object from all vertex groups.

I would say it's the other way around - vertex groups can be removed from the object. Removing object from several vertex groups doesn't sound accurate as it seems to imply several objects can share one vertex group which isn't correct.


text:
Project from view so that the UVs match the background image
Is there a way to use the "project from view" unwrapping method so that the resulting UVs automatically line up with the image, if the same image is used both for the background image and the texture?
At least for me it's a very common workflow to model something on top of a background image and then unwrap with the "project from view method". But I always end up having to scale and move the UV's to match the image, which feels unnecessary, since I already modeled everything to match the BG image perfectly.
Can Blender do this? If not, would it be difficult to write a a script or addon to do this?

There is absolutely no relation between background images and UV space coordinates as far as I know

Last few days back i saw in youtube on how to model a wine bottle..by Miguel Barosso..and the way he teached is what you wanted..i believe..please go to https://youtu.be/ujtbWn-iGIA

Use Project from View Bounds instead of Project from View.


text:
Clear restrict selection
I have several objects disabled for selection in the outliner (the little selection arrow is grayed out). How can I make everything in my scene available for selection without toggling each outliner item on one by one?

In addition to cegaton's useful advice:
If you hold LMB on the top arrow and just drag down, it will turn on all the ones you cross on your way down.
It basically copies the first adjustment you made to all others. Photoshop had that in 2001. I suggested it in 2008, Ton probably forgot and someone else put it in unrelated to my suggestion ( :


text:
Link the text content of two text objects
Is it possible to link text objects in such a manner, that changing the text content on one object will automatically also change the text of another text object.
To clarify, I do not want to link any other properties of those two objects (like fonts for example), only the source text.

is that for animation or during editing ?

During editing is enough in this case.

this a script that uses the scene update handler to synchronize two text object content :

select the two text objects only
copy and paste the script and click run
once you edit one of the text objects the other one will get updated accordingly

import bpy

obj1 = bpy.context.selected_objects[0].name
obj2 = bpy.context.selected_objects[1].name

def link_text_objects(scene):
    obj = bpy.context.active_object
    if obj.type == 'FONT':
        if obj.name == obj1 :
            scene.objects[obj2].data.body = obj.data.body

        else :
            scene.objects[obj1].data.body = obj.data.body

bpy.app.handlers.scene_update_pre.append(link_text_objects)

Nice! This does what I need! To make it more universal do you think it would be difficult to have it affect any number of selected objects (instead of just two)?

maybe will be done with a group , you may want to check this http://blender.stackexchange.com/a/26722/5113

In case somebody is looking at this with Blender 2.8. @Chebhou's script still works if you replace scene_update_pre with depsgraph_update_pre. So it's this:
import bpy

obj1 = bpy.context.selected_objects[0].name
obj2 = bpy.context.selected_objects[1].name

def link_text_objects(scene):
    obj = bpy.context.active_object
    if obj.type == 'FONT':
        if obj.name == obj1 :
            scene.objects[obj2].data.body = obj.data.body

        else :
            scene.objects[obj1].data.body = obj.data.body

bpy.app.handlers.depsgraph_update_pre.append(link_text_objects)

Following @Chebhou's and @Marc-Chéhab's answers, I adopted this script for any number of selected objects. It should work with Blender 2.8+.
import bpy

objs = [obj.name for obj in bpy.context.selected_objects]

def link_text_objects(scene):
    obj = bpy.context.active_object
    if obj.type == 'FONT':
        for o in [o for o in objs if o != obj.name]:
            scene.objects[o].data.body = obj.data.body

bpy.app.handlers.depsgraph_update_pre.append(link_text_objects)


text:
How must I adapt my workflow to work with Scene Referred Data?
I just took the red pill and started watching the real world, in fact the CG real world. I've understood that the default sRGB view workflow is bad.
I'm using the color management LUT bassam-test from troy_s (thanks a lot). But now, how and what must I change in my workflow to really benefit of working with scene referred data?
Is my hdr lighting well suited for that workflow? Must I have to throw all my RGB textures and only find exr ones?
I'm a little bit lost.

I'm a little bit lost.

Don't be. Just learn a little bit at a time and build up your knowledge in smaller steps. We are all learning more at every moment.
I laughed at the red pill.

But now, how and what must I change in my workflow to really benefit of working with scene referred data?

There isn't too much to get too swamped with too soon. Start by experimenting with how larger amounts of light influence your materials.
To do this, simply use an emission mesh with a wide dynamic range view transform. That is, if you are using the testing kit I put together for example, the -10-+6.5 view. You will need to set the emission strength quite high as compared to what you were using under the "Default" previously.
Typical questions and concerns are:

"It looks washed out!"
"How can I control the look?"

The reason the image looks 'washed out' is that it is mapping of scene referred values to the display referred domain, and there is a very wide range to map. To achieve this, a "shaper" or "perceptual quantizer" mapping happens. This is typically a 'flat' look in terms of an artistic sense. While not an aesthetic look for a final shot, it is a wonderful entry point to evaluate your data for a grade.
Once you have rendered out a simple shot, try grading it. I strongly recommend doing a simple, single node grade using the CDL node. It is in the Color Balance node. Simply change from the Lift, Gamma, Gain (which does not work with scene referred data) to ASC-CDL.
The reasons for this are many, and it is a forward looking tool to learn. It is also very easy to get to a pleasant looking shot simply by adjusting power up (1.5-2.5) and slightly adjusting the Slope downwards slightly. Remember that shift key can help you use the interactive sliders on the RGB values with small increments.
0.18 middle grey scene referred ends up mapped to 0.6 in the display referred -10-+6.5 view. You probably would want to grade this down a little, although that will happen naturally when you tweak the power and the slope.

Is my hdr lighting well suited for that workflow?

HDR and IBL lighting is well suited for the workflow, assuming the HDRs are correct and have the proper range of values. This can be tricky to find good quality images. EXR are ideal.

Must i have to throw all my rgb textures and only find exr ones?

Some textures will behave brokenly with proper light levels. This isn't because using a wide dynamic range broke them however, but rather that they were broken to start. If you are using an emission, then you must use scene referred imagery. Diffuse textures and such are not "colors" per se, but rather albedo values, which are a measurement of reflectance. Given that nothing reflects at 100% in the physical reality, diffuse textures of sRGB values 1.0 will likely lead to very strange results, for example.
There are a good number of very talented and wise people here, that you might be able to summon to help you learn. @jtheninja and @gez are two folks with good experience on materials for example.
Hope this helps. Take small steps and hopefully you will enjoy the results.
For the ones interested by the subject, check the Wide Dynamic Range post


text:
How do I remove the overlap from merged meshes?
I have recently decided to delve back into 3D modeling, I am a hobbyist I guess you could say.  I have been trying to find a solution for this particular problem for days now.  I have scoured this as well as other forums and have yet to find an answer to this dilemma.  This is my first post here so I hope I don't make too much of a fool of myself :P
I am currently trying to merge three rectangular cubes to form a symbol:

The problem arises when I goto render the picture:

I have tried Joining the objects then going back with the Knife and removing doubles, which seems to be the answer to this, but I keep getting the overlap.
I am sure it is a simple fix but I have probably burned myself out on finding it.
Thanks in advance for any help or advice.
If I have managed to miss another answer to this in my search could you please link it.

You could do it with the TinyCAD addon or with some extrudes.
If you want to start with your 3 parallelepipeds you could use the TinyCAD addon:

Download and istall the addon.
Join your parallelepipeds with a ctrlJ, and go in Edit mode.
Select all and press W > TinyCAD > XALL.
Keep everything selected and press W > Remove Doubles.
Delete the inner vertices so that you won't have any inner edges in the final object.
Fill all the faces.

If you want to do it with some extrudes, you could:

Start with a plane, create an edge loop on its middle and tilt it with GG.
Bevel the middle edge loop with ctrlB and create 2 new edge loops.
Extrude the plane.
Select a face and press ctrlaltspacebar to create a new custom Transformation Orientation (named "Face.001" by default).
Keep this new orientation selected.
Select one of the faces you need to extrude, press E and Enter right away.
Move this new face along the Face.001 Y axis.
Same thing for the other face.

Thank you very much for your help with this.  After a bit of fumbling around with it I figured out I had to Join the parallelepipeds prior to switching to Edit Mode for the rest of the steps mentioned above.  This was, I am sure, one of many hurdles in my self-assigned project and it is nice to have a place to go for advice.

oh ok I thought you'd know you would have to join   ;)

I am learning/relearning this world, again, after a few years.  I am mainly doing it for fun but you never know where it can go.  I am mainly using projects to learn more about the program. If there are any tutorials or informational material you would recommend that would be cool.  I have googled about 100 tutorials and courses but just use them as needed.

hard to say, at the beginning I followed a lot of random tutorials that seem interesting, then a thing that helps a lot is to have my own project, for example create a fake animation movie trailer, which forced me to solve the problems I came across, like make a character walk, a camera follow a path, etc... I think it's the best way to learn: cope with problems to solve  ;)


text:
Opacity animation disappears in render
I'm using opacity animation to make an animated text fade out. It's working in the Video Sequence Editor, but when I render the video it doesn't work; the text doesn't fade at all.

I've tried rendering it out in different formats, including Quicktime, MPEG & H.264, but the Quicktime format is the only one I've actually been able to view afterwards.
I'm using Bender 2.77 and I've created the text animations in the 3D View as scenes, which I've then added to the VSE. I've also inserted keyframes to adjust the opacity at the end of each animation.

Try adding more info to your question. Not sure exactly how you are rendering this or what rendering engine you are using, but video file formats generally do not support alpha channels and as such do not support transparency. Have you tried rendering to a PNG sequence instead?

If possible at all attached the animated text so that we can take a look at it. It's probably a simple step you have missed. Use this link to upload the blend file http://blend-exchange.giantcowfilms.com/

The most useful thing would be a screen-shot of the section of the VSE where the animation isn't working. I have a pretty good idea what's wrong, but I'd like to confirm...

I think, @DuarteFarrajotaRamos is on the right track with the alpha problem. Try to just place a solid black Color Strip underneath to confirm this... As I think I read somewhere that only Quicktime is allowing for transparent backgrounds in a video and the fading using opacity is probably resulting in problems in other formats.

Possible duplicate of Can't change opacity of scene strip in Video Sequence Editor

thanks very much for all the responses :) i am rushing from one meeting to another at the moment so i will respond in more detail in a few hours, but briefly:

i'm using the blender render engine; saving to quicktime format, with the RGBA channel selected. i will send files later. thanks!!

@Samoth - i did have this problem at first also, but used the information on the link you've posted to do the workaround for the bug, and it worked - but only when i'm looking at the .blend file in blender. when i render it out to .mov, the fade isn't there.

@hawkenfox here is the file:  - please understand that this is my first attempt at using blender, so i'm sure i've done all kinds of terrible things ...
in my latest render, the beginning animations (where the text slides in from the right) did not work. this had worked in previous renders, & i'm not sure what i might have changed that would have affected that. i tried rendering to different formats to see if i could find one where the opacity worked, but i didn't.

@Matt do you want a screenshot, or can you look at the file i just uploaded? :)

A screenshot would be very helpful. I usually can't download Blender files when I have access to StackExchange.

@Matt http://creative-catalyst.com/images/blender_screenshot_130516.png

i saved it out to pngs & the animations & opacity all works. if i do it this way, would it be best to then import the pngs to a video editor (i only have imovie) & add the audio there, or is there a way that would work to do it in blender? (or would that be silly/more difficult?).

I highly recommend rendering ANY animation out to images (png or jpg, if you don't need alpha) and then putting them together in the VSE. It's not silly at all. If you're rendering to a video and the render fails part way through, you lose the WHOLE thing. If you're rendering to images and it fails part way through, you at least have all the images you already rendered, and can just start from the last one you have.

You can import them into Blender with the VSE and even add audio there. Blender is a bit more cumbersome, and not as well documented as others, but it will definitely work. It's what they've used to edit all the Blender open movies ;-)

It's really strange that it worked rendered to images, but not to a video....

hi @Matt - i just tried your suggestion, importing the PNG sequence into the VSE, adding the audio & rendering it to Quicktime. this rendered much faster than before (when i was rendering the animation directly to video) BUT in the resulting .mov file, the fades are not there. they are there in the PNGs, they are there when i play it in blender, but they are not there in the rendered file :(

I KNOW WHAT IT ISSSSSS!!! I'll type it up in an answer....

@helen, yes compiling rendered frames into a video is MUCH faster than rendering them for the first time ;-)

The reason your fades are not working is two-fold.
Firstly, the Quicktime format does not support an alpha channel (I don't know of a video format that does... maybe GIF?).
Secondly, your RGBA colors are not pre-multiplied, but are "straight alpha." A bit of explanation here.
Consequently, when your frame gets put into the video format, the alpha portion of that image is simply discarded, leaving you with grey text that's no longer transparent. This didn't happen when you rendered it to images because PNG does support an alpha channel. Thus, you had text that was still fully grey, but it was also transparent. I'll bet that if you rendered to JPGs, you'd lose the fading as well because JPG doesn't support alpha. The question would be whether Blender would pre-multiply your alpha or just discard the alpha channel. I suspect it'd do the same thing that it did with the video and just discard it.
There are two solutions. One is to render pre-multiplied alpha. It's not going to be easy to figure out how to do this because it changed recently in the VSE. And there are a couple of different places in the rendering pipeline that pre-multiplication might happen. If anyone else knows, feel free to edit my answer. But this is a poor solution because the background of your video is incidental, not deliberately chosen. It's only fading to black because all the pixels that aren't rendered HAPPEN to be black when the alpha is discarded. This is a reasonable assumption to make, but it's an assumption not a decision.
The most correct solution is to make the decision of what to fade TO. You really ought not think in terms of "fade out." Rather, you should always think "fade to..." Even in your video, you're not wanting to "fade out." You're wanting to "fade to black." There are a number of ways to accomplish this, depending on what's what's best for your project. The option I'd recommend is to add an Effect Strip -> Color to the bottom layer, and set the color to black. Thus, when your text becomes transparent, there's still something behind it to render.
You could, of course, set the color of the Effect Strip to whatever color you want, and it'd work just as well.
I hope that helps!

thank you very much, Matt! i'm happy to know there is a reason & i will try to remake it using the second, most correct, solution that you give, adding an effect strip. i will let you know how it goes :)

it worked! :) i put a black strip under the text, & also when i was checking all the render settings i saw that i could choose PNG instead of JPG for the video codec, so i selected this. then rendered it to quicktime again & now the fades are happening. thanks so much for your help with this :)

sorry, didn't realise i had to do that! (you're my first answer :) )


text:
Only a shadow of the 3d object over the background is visible in the render

I'm new to blender. Actually very new. I searched for this in the discussions. But none of them solved the problem I have not done anything with nodes. I guess I'm going to watch some tutorials for that. But the problem is everything is completely fine in the rendered view option but as soon as I render image it renders like that below. I tried changing a lot of things, nothing changed.Plzz help me out!
Here is the blend file:


text:
Get points of Bezier Curve in coordinate space of the scene
Sorry if the title is confusing, I wasn't sure how to best describe what I am trying to do.
Basically, I'm trying to create Bezier Curves that "grow" off of each other. For example, I would make one curve, deform it in whatever way, and then create a second curve that starts at a random point along the first curve, like this:

Obviously, I'm trying to do all of this programmatically in python.
I was able to pull the points of the first curve using the code suggested in this comment: Getting the list of points that describe a Curve without converting to mesh along with some of my own code.
However, the output of this seems to always be between -1 and 1 (though it goes a little over on both ends) no matter where in the scene I place it. This suggests to me that the exported points are in some relative space and not in the coordinate space used by the scene.
Does anyone know how to output the points of a curve in X, Y, Z coordinates of the scene? Or at least how to transform those points into the coordinates of the scene?
Thank you!

The curve data, like mesh data, is in local coordinates, whereas you want global coordinates, which can be obtained by multiplying by the curve objects matrix_world. http://blender.stackexchange.com/a/6156/15543

Perhaps the following code gives you an explicit example of how to interpolate points on a Bezier curve.  (I almost forgot the matrix_world that batFINGER has already explained is very important)
import bpy
from math import *

def interpBez3(bp0, t, bp3):
    # bp1, HR, HL, bp2

    return interpBez3_(bp0.co, bp0.handle_right, bp3.handle_left, bp3.co, t)
#    return interpBez3_(bp0.co, bp0.handle_left, bp3.handle_right, bp3.co, t)

def interpBez3_(p0, p1, p2, p3, t):
    r = 1-t
    return (r*r*r*p0 +
            3*r*r*t*p1 +
            3*r*t*t*p2 +
            t*t*t*p3)

def interpBlenderSpline(spline, i1, t2):

    bp1 = spline.bezier_points[i1]
    bp2 = spline.bezier_points[i1+1]
    return interpBez3(bp1, t2, bp2)

def mission1(obj, t):
    """ mathematically correct spline interpolation """

    i1 = floor(t)

    curve = obj.data

    bpy.context.scene.cursor_location = obj.matrix_world * interpBlenderSpline(curve.splines[0], i1, t-i1)

def mission2(obj, t):
    """ spline interpolation that matches the resolution_u setting inside blender """
    i1 = floor(t)
    t2 = t - i1
    spline = obj.data.splines[0]

    res = obj.data.render_resolution_u or obj.data.resolution_u
    t3 = t2*res
    t3i = floor(t3) / res
    t3f = t3 - floor(t3)

    p8 = interpBlenderSpline(spline, i1, t3i)
    p9 = interpBlenderSpline(spline, i1, t3i + 1/res)

    p = (1-t3f)*p8 + t3f*p9

    bpy.context.scene.cursor_location = obj.matrix_world * p

mission1(bpy.context.active_object, 0.7)

The mission2 function is if you want the point to match how blender chops up the spline into line segments instead of being on the mathematically precise bezier segment.

Thanks Mutant. How to change it to respect curve resolution ?

I'm going to need you to define what you mean by "respect curve resolution" .

For default curve object, default resolution is 12 and when you decrease/increase resolution, curve object changes. So interpolated points have to change also.

For Blender 2.8 and later the following update to the code is helpful. I also added the ability to give a fraction from 0 to just less than 1 to allow interpolation for the entire curve.
from math import *
def interpBez3(bp0,t,bp3):
    return interpBez3_(bp0.co,bp0.handle_right,bp3.handle_left,bp3.co,t)

def interpBez3_(p0,p1,p2,p3,t):
    r=1-t
    return( r*r*r*p0+
            3*r*r*t*p1+
            3*r*t*t*p2+
            t*t*t*p3 )

def interpBlenderSpline(spline,i1,t2):
    bp1=spline.bezier_points[i1]
    bp2=spline.bezier_points[i1+1]
    return interpBez3(bp1,t2,bp2)

def mission1(obj,frac):
    curve=obj.data
    numpoints=len(curve.splines[0].bezier_points)
    t=frac*(numpoints-1)
    i1=floot(t)
    bpy.context.scene.cursor.location=obj.matrix_world @ interpBlenderSpline(curve.splines[0],i1,t-i1)

mission1(bpy.context.active_object,0.7) # works from 0 to 0.9999999 or so

The most important changes were the '@' for matrix multiplication with a vector and the cursor location is ....cursor.location and not .....cursor_location.


text:
Mixing image texture makes everything transparent
I am trying to create a material where I can place in 2 images (one with white space, and one with just an outline) where the outline gets laid over(with alpha cut out) a material/shader, that would be defined by the white space image.

I have both halves working separately correctly, but when I use a mix shader, they mix correctly but become transparent (when I want it solid).
Node Map

Both Together

(First image is the node map used. Top image texture is outline and bottom is white space)

(second image is the output using the monkey head. There is aweful transparency over everything)

Think I got this right:

I would have posted the 2 images in the same post, but I am limited to only 2 images(says StackExchange)

Whoops. The forum post I read for packing images did not state it required to be saved too, I figure that was built in on that or something. Re-uploaded and edited into original post above.


text:
Can the full features of Blender be used with a trackpad?
I'm not interested recommendations for the best hardware, but whether Blender's full functionality-- all that zooming and selecting stuff-- can be realized with only a trackpad.

Short answer, yes, but it gets quite cumbersome. Best to invest in a mouse and use the emulation settings available.

I work with a trackpad all the time, but I am getting a mouse soon because it is definitely easier to use.

You can use it to an extent, but from experience, it quickly becomes quite cumbersome. You tend to lose a lot of precision as the space to move in is a bit cramped and overall it is not worth taking the time to get adjusted to and or customizing it to work better.
For example: To zoom, I have to swipe the edge of the trackpad, this quickly gets annoying and it often passes the point where I want to stop.
I highly recommend investing in a mouse instead and using the Emulate 3 Button Mouse option in the user preferences.
Related:

How do you unselect vertices without a middle mouse button?
How to emulate a Number Pad and 3 Button Mouse?
Zoom in and out without a mouse wheel
How can I control the viewport without a mouse?

I think you are incorrect regarding zooming. Zooming is performed using pinching.

@Jonny I was using an example, on my laptop, I have to swipe the trackpad.

Just saying that I am using pinching all the time in Blender on my Mac. It's possible that older OSes and Macs don't support the gesture.

What does the emulate 3 button mouse do?

@AnsonSavage It lets alt + LMB act like the MMB (left and middle mouse buttons).

On modern Mac OS X, it seems you can:

Two-finger vertical scroll to rotate along horizontal axis perpendicular to view
Two-finger "spin" to rotate around up axis
or Two-finger horizontal scroll to rotate around up axis
Two-finger pinch to zoom
or CTRL + two-finger vertical/horizontal scroll to zoom
SHIFT + two-finger vertical scroll to pan along up axis
SHIFT + two-finger vertical scroll to pan along horizontal axis perpendicular to view
RIGHT click and drag to translate selected object
CTRL click and drag to lasso select

This is now (as of 2015) the best answer. Tested in blender 2.74 and works like a charm. Wish I had had this years ago. @Alec is there also a good mapping now for what was the numpad functions?

Just wanted to add to @Alec's answer that there is a checkbox for "Natural Trackpad Direction". You can find this in the preferences panel, inside the Input tab. This option seems to invert the direction in which the rotation happens when you do a two-finger scroll.
It seems to be off by default, but to me it made more sense with it on. It feels more consistent with the way the mouse rotates.

Wish I had seen this earlier. Spent way too much time figuring out how to do this.

@Jose Vazquez's answer was really helpful to me. Just to update that, in Blender 2.83.0, the "Natural Trackpad Direction" option is no longer inside the Input tab. It has been moved to the Navigation tab instead.

Simplest solution I've found so far (and I've done this on Windows too) is User Preferences > Input > 3D View > Rotate View and Move view. Remap the "Center Mouse" to ~ (tilde) and ⇧ Shift~ respectively.
YouTube video that showed me this option: https://www.youtube.com/watch?v=sYz3EAxmyrQ

In addition to @alec Karabiner Elements can be useful to access the numpad. Here is part of my preferences.json file which causes fn+1..0 to send 1..0 from the numpad so views can be selected in Blender without a physical numpad or always using the menus:
            "simple_modifications": [
                {
                    "from": {
                        "key_code": "1",
                        "modifiers": {
                            "mandatory": [
                                "fn"
                            ]
                        }
                    },
                    "to": {
                        "key_code": "keypad_1"
                    }
                },
                {
                    "from": {
                        "key_code": "2",
                        "modifiers": {
                            "mandatory": [
                                "fn"
                            ]
                        }
                    },
                    "to": {
                        "key_code": "keypad_2"
                    }
                },
                {
                    "from": {
                        "key_code": "3",
                        "modifiers": {
                            "mandatory": [
                                "fn"
                            ]
                        }
                    },
                    "to": {
                        "key_code": "keypad_3"
                    }
                },
                {
                    "from": {
                        "key_code": "4",
                        "modifiers": {
                            "mandatory": [
                                "fn"
                            ]
                        }
                    },
                    "to": {
                        "key_code": "keypad_4"
                    }
                },
                {
                    "from": {
                        "key_code": "5",
                        "modifiers": {
                            "mandatory": [
                                "fn"
                            ]
                        }
                    },
                    "to": {
                        "key_code": "keypad_5"
                    }
                },
                {
                    "from": {
                        "key_code": "6",
                        "modifiers": {
                            "mandatory": [
                                "fn"
                            ]
                        }
                    },
                    "to": {
                        "key_code": "keypad_6"
                    }
                },
                {
                    "from": {
                        "key_code": "7",
                        "modifiers": {
                            "mandatory": [
                                "fn"
                            ]
                        }
                    },
                    "to": {
                        "key_code": "keypad_7"
                    }
                },
                {
                    "from": {
                        "key_code": "8",
                        "modifiers": {
                            "mandatory": [
                                "fn"
                            ]
                        }
                    },
                    "to": {
                        "key_code": "keypad_8"
                    }
                },
                {
                    "from": {
                        "key_code": "9",
                        "modifiers": {
                            "mandatory": [
                                "fn"
                            ]
                        }
                    },
                    "to": {
                        "key_code": "keypad_9"
                    }
                },
                {
                    "from": {
                        "key_code": "0",
                        "modifiers": {
                            "mandatory": [
                                "fn"
                            ]
                        }
                    },
                    "to": {
                        "key_code": "keypad_0"
                    }
                }
            ],


text:
Connecting two screws?
I'm new to blender and I am looking for an easy way to connect two screws. Currently I have this double helix structure that I made by constructing two screws from circles:
I am looking to connect one of the sides of the double helix like this:

I've tried making a tube using a bezier circle/path but can't find a way to attach it to the ends of the screw easy and seamlessly.

Look at Bridge Edge loops https://docs.blender.org/manual/en/latest/modeling/meshes/editing/edges.html#bridge-edge-loops

Move both the ends of the helix toward their common centre using proportional editing, then remove doubles and adjust with proportional editing.

Thanks! I’ll have to figure out how to do that.


text:
How to select identical UV island at one time?

I have many similar uv island as in picture, I just want to select those hook-like ones, they have same vertice count, how?

Personally I find Blender's default UV tools rather sad and lacking, especially coming from Modo. However, if you have $20 to spare, UV Toolkit (https://blendermarket.com/products/uv-toolkit) gets you pretty close to most major apps. It also has "select similar islands," which is exactly what you are looking for.

I agree with you , thanks for the advice (at last I had to get UVpackmaster to achieve my desired result , just needed to have all the uvs packed tightly)


text:
Bizarre Outer Shell on a model? Only Appears in pose and object mode
I'm new to blender (problem 1, I know) and I've been following a tutorial on character modeling, up until now without any issues that I couldn't solve on my own, but now I've run into a tough one. This issue didn't become prevalent until I started rigging the model you see.

This is the model when in edit mode (resting pose as I've learned) but as soon as I attempt any posing with it I get a weird issue where a "ghost" starts to emerge from the body and typically follows the pose the character is doing but to a more twisted extent:

Now, there are two things to note, one being I am 90% sure this has something to do with backfaces, as this screenshot shows what it looks like after I turned on the "Backface Culling" option (before I turned it on the "Ghost" appeared as a solid version of the model with no textures, this has been the only thing to affect the ghost thus far), the other that this problem didn't occur until after I rigged it, chances are I just f'd up the rigging but I can't be too sure, so if anyone knows how to fix this issue I would be grateful!
edit: File can be found here! :

could you please share your file? https://blend-exchange.giantcowfilms.com/

The Ghost of Scaling Discrepancies, perhaps?

Uploaded the file! Hopefully that sheds some light

Your issue lies in the topology. You have double vertices almost everywhere (multiple vertices at the same position in space). This would probably ruin the weight painting leaving parts of the mesh stretched as shown in your pictures. On top of that, back face culling is enabled so any back facing normals will not be shown. This meant that very small slithers of the mesh was being shown making it look like as you said, a ghost mesh.
To fix it you will probably have to remove double via W in edit mode, and then the remove doubles button. Probably a good idea to recalculate your normals with ctrl+n. Then you will likely have to redo the weight painting on the bones.


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weird camera path with good marker tracking solve error
I have a drone footage taken with Phantom 3 Pro and I want to solve the camera path. The markers are fairly stable with a solve error less than 1. Still the camera path is pretty much crazy. I used LocScale for the motion model of the markers, since with Perspective the tracking was impossible to follow.
Here is the youtube link for the screen capture movie:
https://www.youtube.com/watch?v=S8uNgkwqE_s&feature=youtu.be
Any ideas what am I doing wrong?
Thanks!

You can see that the end of the camera move is tracked well, this is because there markers with different depth which are very consistent. In the beginning there is little depth information (since the markers are only on the tower) and most of them removed very quickly. You don't have a frame with the beginning markers in correlation to anything in the background.

Have you tried using different keyframes for the camera solve?


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Volumetric scatter shader does not show light focused through lens correctly
I am trying to make the light from a convex lens shine through haze in a volumetric scatter cylinder like this: https://www.behance.net/gallery/53917965/LENSES-TEST
I can see that my lens does concentrate a beam of light on the plane below the lens, however the volumetric cylinder below the lens depicts a perfectly even distribution of light...

Is there a way to make the volumetric light look like the scene linked above? Here is a wire frame to make it easier to understand how the scene is set up...

And the node setup for the volumetric scatter cylinder...

Here is how it looks if I enlarge the volumetric cylinder enough to envelope the entire scene. There should be a narrowing beam of light below the lens...

Seems to be working for me, is it possible you could upload your .blend?

@gandalf3 - added blend file

It is working, it's just not visible (yet).
Try using the branched path tracer to sample more volume bounces per sample:

Switch to the Branched Path Tracing integrator
Set the number of volume samples to something large (you may also want to increase the samples for some of the other passes as well)
Set the number of Anti-Aliasing samples. These correspond to the number of initial samples cast from each pixel (See What is branched path tracing and how is it useful? for more detail)
Note the total number of samples per pass (21000 volume samples, and still not nearly enough!).

Here is your file rendered with the settings shown above (to get a better caustic on the diffuse plane, try increasing the number of diffuse samples a bit):

Cheers for the solution. It looks like branch path tracing cannot use GPU and my CPU bogs after the first few samples, freezing my computer. Same result even if I limit the number of cores dedicated to rendering. Will have to try in the future with a better PC.

@SailorJ The branched path method takes longer per sample, but requires fewer samples. So what looks like bogging down when compared to the progressive method is actually normal. It should work on GPU though, if I'm not mistaken. What happens when you try to switch to GPU?

@SailorJ Also, you might want to give luxrender and its bidirectional path tracer a try. Cycles does backwards path tracing (that is, it traces light paths from the camera until they hit a light source), which is more efficient than forward path tracing (trace rays from lights until they hit the camera) but not really the best for caustics and fancy optical stunts.

My mistake. I thought that all four processors pegged at 100% meant I was rendering the view port with the CPU. GPU is working for the actual render and doesn't freeze. I had looked at Luxrender for a prism refraction (rainbow) effect. Will try with this too. Thanks again.