def plot3dOnFigure(ax, pixels, colors_rgb,axis_labels=list("RGB"), axis_limits=((0, 255), (0, 255), (0, 255))):
    """Plot pixels in 3D."""

    # Set axis limits
    ax.set_xlim(*axis_limits[0])
    ax.set_ylim(*axis_limits[1])
    ax.set_zlim(*axis_limits[2])

    # Set axis labels and sizes
    ax.tick_params(axis='both', which='major', labelsize=14, pad=8)
    ax.set_xlabel(axis_labels[0], fontsize=16, labelpad=16)
    ax.set_ylabel(axis_labels[1], fontsize=16, labelpad=16)
    ax.set_zlabel(axis_labels[2], fontsize=16, labelpad=16)

    # Plot pixel values with colors given in colors_rgb
    ax.scatter(
        pixels[:, :, 0].ravel(),
        pixels[:, :, 1].ravel(),
        pixels[:, :, 2].ravel(),
        c=colors_rgb.reshape((-1, 3)), edgecolors='none')

    return ax