some examples for setting expressions in the python api for the nuke rotopaint system

roto_python_examples.nk

set cut_paste_input [stack 0]
push $cut_paste_input
RotoPaint {
 cliptype none
 curves {{{v x3f99999a}
  {f 0}
  {n
   {layer Root
    {f 2097152}
    {t x44800000 x44428000}
    {a pt1x 0 pt1y 0 pt2x 0 pt2y 0 pt3x 0 pt3y 0 pt4x 0 pt4y 0 ptex00 0 ptex01 0 ptex02 0 ptex03 0 ptex10 0 ptex11 0 ptex12 0 ptex13 0 ptex20 0 ptex21 0 ptex22 0 ptex23 0 ptex30 0 ptex31 0 ptex32 0 ptex33 0 ptof1x 0 ptof1y 0 ptof2x 0 ptof2y 0 ptof3x 0 ptof3y 0 ptof4x 0 ptof4y 0 pterr 0 ptrefset 0 ptmot x40800000 ptref 0}
    {layer Layer1
     {f 2097664}
     {t x44800000 x44428000}
     {a pt1x 0 pt1y 0 pt2x 0 pt2y 0 pt3x 0 pt3y 0 pt4x 0 pt4y 0 ptex00 0 ptex01 0 ptex02 0 ptex03 0 ptex10 0 ptex11 0 ptex12 0 ptex13 0 ptex20 0 ptex21 0 ptex22 0 ptex23 0 ptex30 0 ptex31 0 ptex32 0 ptex33 0 ptof1x 0 ptof1y 0 ptof2x 0 ptof2y 0 ptof3x 0 ptof3y 0 ptof4x 0 ptof4y 0 pterr 0 ptrefset 0 ptmot x40800000 ptref 0}
     {curvegroup Ellipse1 512 bezier
      {{cc
        {f 8192}
        {px 1
	 {xc2576420 0}
	 {x445de000 x44660000}
	 {x42576420 0}
	 {0 xc2626fd0}
	 {x44764000 x447fa000}
	 {0 x42626fc0}
	 {x42576420 0}
	 {x445de000 x448ca000}
	 {xc2576420 0}
	 {0 x42626fc0}
	 {x44458000 x447fa000}
	 {0 xc2626fd0}}}
       {cc
        {f 8192}
        {p
	 {{{1 xc2576420}}
      {{1 0}}}
	 {{{1 0}}
      {{1 0}}}
	 {{{1 x42576420}}
      {{1 0}}}
	 {{{1 0}}
      {{1 xc2626fd0}}}
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	 {{{1 0}}
      {{1 x42626fc0}}}
	 {{{1 x42576420}}
      {{1 0}}}
	 {{{1 0}}
      {{1 0}}}
	 {{{1 xc2576420}}
      {{1 0}}}
	 {{{1 0}}
      {{1 x42626fc0}}}
	 {{{1 0}}
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      {tx 1 x445de000 x447fa000}
      {a osw x41200000 osf 0 str 1 spx x44800000 spy x44428000 sb 1 tt x40e00000}}
     {layer Layer2
      {f 2097664}
      {t x44800000 x44428000}
      {a pt1x 0 pt1y 0 pt2x 0 pt2y 0 pt3x 0 pt3y 0 pt4x 0 pt4y 0 ptex00 0 ptex01 0 ptex02 0 ptex03 0 ptex10 0 ptex11 0 ptex12 0 ptex13 0 ptex20 0 ptex21 0 ptex22 0 ptex23 0 ptex30 0 ptex31 0 ptex32 0 ptex33 0 ptof1x 0 ptof1y 0 ptof2x 0 ptof2y 0 ptof3x 0 ptof3y 0 ptof4x 0 ptof4y 0 pterr 0 ptrefset 0 ptmot x40800000 ptref 0}
      {curvegroup OpenSpline1 1049088 bezier
       {{cc
	 {f 1056800}
	 {px 1
	  {xc0c00000 x41c00000}
	  {{a osw
	 {{1 1}}	   osf
	 {{1 0}}}       x43220000 x44930000}
	  {x40c00000 xc1c00000}
	  {xc2880000 x41200000}
	  {{a osw
	 {{1 1}}	   osf
	 {{1 0}}}       x43a50000 x44618000}
	  {x42880000 xc1200000}
	  {xc0800000 xc1200000}
	  {{a osw
	 {{1 1}}	   osf
	 {{1 0}}}       x441e8000 x446b0000}
	  {x40800000 x41200000}
	  {0 0}
	  {{a osw
	 {{1 1}}	   osf
	 {{1 0}}}       x439d0000 x44994000}
	  {0 0}}}       idem}
       {tx 1 x43b40000 x4484a000}
       {a osbe 0 osee 0 osw x41200000 osf 0 str 1 tt x41200000}}
      {cubiccurve Brush1 512 catmullrom
       {cc
        {f 2080}
        {px 1
	 {x44bf4000 x4499c000 x3e352c00}
	 {x44be0000 x4499c000 x3eefba00}
	 {x44ba4000 x4499c000 x3f20a800}
	 {x44b22000 x44974000 x3f332c00}
	 {x44a96000 x44938000 x3f3a2e00}
	 {x44a96000 x448ac000 x3f3e6f00}
	 {x44b4a000 x4483e000 x3f40b000}
	 {x44c08000 x447b4000 x3f417000}
	 {x44bea000 x446d8000 x3f473100}
	 {x44afa000 x4455c000 x3f49f200}
	 {x44a3c000 x443cc000 x3c400000}
	 {x44a46000 x443b8000 0}}}
       {tx 1 x44b352ab x4482d555}
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    {curvegroup Bezier1 512 bezier
     {{cc
       {f 8192}
       {px 0
        {0 xc0000000}
        {x443c0000 x443c0000}
        {0 x40000000}
        {xc2480000 x42580000}
        {x442f8000 x43dc0000}
        {x42480000 xc2580000}
        {xc1c00000 xc2280000}
        {x446f8000 x43b00000}
        {x41c00000 x42280000}
        {x42080000 xc1900000}
        {x44780000 x442d8000}
        {xc2080000 x41900000}
        {x41f00000 x40000000}
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     {tx 0 x44548000 x44186666}
     {a osw x41200000 osf 0 str 1 spx x44800000 spy x44428000 sb 1 ltn 0 ltm 0 tt x40800000}}}}}}
 toolbox {selectAll {
  { selectAll str 1 ssx 1 ssy 1 sf 1 }
  { createBezier str 1 ssx 1 ssy 1 sf 1 sb 1 }
  { createBezierCusped str 1 ssx 1 ssy 1 sf 1 sb 1 }
  { createBSpline str 1 ssx 1 ssy 1 sf 1 sb 1 }
  { createEllipse str 1 ssx 1 ssy 1 sf 1 sb 1 tt 7 }
  { createRectangle str 1 ssx 1 ssy 1 sf 1 sb 1 }
  { createRectangleCusped str 1 ssx 1 ssy 1 sf 1 sb 1 }
  { brush h 0 str 1 ssx 1 ssy 1 sf 1 sb 1 tt 17 }
  { eraser h 0 src 2 str 1 ssx 1 ssy 1 sf 1 sb 1 }
  { clone h 0 src 1 str 1 ssx 1 ssy 1 sf 1 sb 1 tt 19 }
  { reveal h 0 src 3 str 1 ssx 1 ssy 1 sf 1 sb 1 }
  { dodge h 0 src 1 str 1 ssx 1 ssy 1 sf 1 sb 1 }
  { burn h 0 src 1 str 1 ssx 1 ssy 1 sf 1 sb 1 }
  { blur src 1 str 1 ssx 1 ssy 1 sf 1 sb 1 }
  { sharpen h 0 src 1 str 1 ssx 1 ssy 1 sf 1 sb 1 }
  { smear h 0 src 1 str 1 ssx 1 ssy 1 sf 1 sb 1 }
} }
 toolbar_brush_hardness 0.200000003
 toolbar_source_transform_scale {1 1}
 toolbar_source_transform_center {1024 778}
 colorOverlay {0 0 0 0}
 lifetime_type "all frames"
 motionblur_shutter_offset_type centred
 brush_spacing 0.05000000075
 brush_hardness 0
 source_black_outside true
 name Roto
 selected true
 xpos -10628
 ypos 1382
}
NoOp {
 inputs 0
 name Test
 selected true
 xpos -10631
 ypos 1480
 addUserKnob {20 Test}
 addUserKnob {22 test l Test T "import sys\nsys.path.insert(0, nuke.root()\['project_directory'].evaluate())\nimport rotopaint_examples\nreload(rotopaint_examples)\nrotopaint_examples.start()" +STARTLINE}
}

rotopaint_examples.py

from __future__ import print_function
import nuke
import nuke.rotopaint as rp
import _curvelib as cl

'''
# Nuke rotopaint API reference
https://learn.foundry.com/nuke/developers/120/pythonreference/
# nuke python devguide on rotopaint
https://learn.foundry.com/nuke/developers/120/pythondevguide/rotopaint.html
'''

def parse_layer(root_layer, elements, parents):
    # recursively gather all shapes and strokes in specified roto layer
    for element in root_layer:
        if isinstance(element, rp.Shape):
            print('adding shape element {0}'.format(element.name))
            elements['Shapes'].append([element, parents])
        elif isinstance(element, rp.Stroke):
            print('adding Stroke element {0}'.format(element.name))
            elements['Strokes'].append([element, parents])
        elif isinstance(element, rp.Layer):
            parent_names = [l.name for l in parents]
            parent_names.reverse()
            print('Getting contents of layer element {0}\nwith parent {1}'.format(
                element.name, '/'.join(parent_names)))
            parents_copy = parents[:]
            parents_copy.insert(0, element)
            elements = parse_layer(element, elements, parents_copy)
    return elements

def get_elements(roto_node):
    # Get all shape stroke and layer elements from specified Roto, RotoPaint, or SplineWarp node
    elements = { 
        'Shapes': [],
        'Strokes': [],
        }   

    root_layer = roto_node['curves'].rootLayer
    elements = parse_layer(root_layer, elements, [root_layer])
    return elements


def set_expressions(roto_node, shapename):
    # get a specific shape
    shape = roto_node['curves'].toElement(shapename)
    #print(help(shape))

    # We will set an expression on the translate, rotate, and scale for this shape
    xform = shape.getTransform()

    # Find all the things you can do with this object with
    print(help(xform))

    # First we have to create an _curvelib.AnimCurve object to hold our animation curve.
    translation_curve_x = cl.AnimCurve()
    translation_curve_y = cl.AnimCurve()
    rotation_curve = cl.AnimCurve()
    scale_curve = cl.AnimCurve()

    # To set an expression on our curve we have to set the expressionString and useExpression to True
    translation_curve_x.expressionString = 'frame'
    translation_curve_y.expressionString = 'frame%2'
    rotation_curve.expressionString = 'frame'
    scale_curve.expressionString = 'frame/100+0.5'

    # set useExpression=True for all curves
    for curve in [translation_curve_x, translation_curve_y, rotation_curve, scale_curve]:
        curve.useExpression = True

    # Now we overwrite the animcurves on the shape
    xform.setTranslationAnimCurve(0, translation_curve_x)
    xform.setTranslationAnimCurve(1, translation_curve_y)
    # Index value of setRotationAnimCurve is 2 even though there is only 1 parameter...
    # http://www.mail-archive.com/nuke-python@support.thefoundry.co.uk/msg02295.html
    xform.setRotationAnimCurve(2, rotation_curve)
    xform.setScaleAnimCurve(0, scale_curve)
    xform.setScaleAnimCurve(1, scale_curve)


def start():
    nuke.root().begin()
    roto_node = nuke.toNode('Roto')
    
    # # get contents of roto node
    # elements = get_elements(roto_node)
    # print(elements)

    set_expressions(roto_node, 'Layer1/Ellipse1')



if __name__=='__main__':
    start()