SplineTest: calculateSteps(): calculate t each time, don't use dt.
SplineTest: calculateSteps(): calculate t each time, don't use dt.

Seems to be more precise judging by the changed test..

LebedevRI/rawspeed,LebedevRI/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed,darktable-org/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed