Solved Gradient Interpolation Error in 2024 release

danielsian

With the new version 2024 I'm no longer able to set the interpolation knots in a gradient this way:

knot[c4d.GRADIENTKNOT_INTERPOLATION] = c4d.GRADIENT_INTERPOLATION_SMOOTHKNOT

as the console returns

AttributeError: module 'c4d' has no attribute 'GRADIENT_INTERPOLATION_SMOOTHKNOT'

But this way it works:

knot[c4d.GRADIENTKNOT_INTERPOLATION] = 2

However, from the new documentation, it should work as it always has been:
https://developers.maxon.net/docs/py/2024_0_0/modules/c4d/CustomDataType/Gradient/index.html#Gradient.SetData

Am I missing anything?

BTW I'm experimenting with this example provided in the Extended Python SDK:

"""
Copyright: MAXON Computer GmbH
Author: Maxime Adam, Ferdinand Hoppe

Description:
    - Showcases the usage of the custom data type `c4d.Gradient`.
    - Creates a material with a gradient shader in the color channel.

Class/method highlighted:
    - c4d.BaseMaterial
    - c4d.BaseShader
    - c4d.Gradient
    - c4d.BaseContainer

"""

import c4d

def main():
    # Create a new material and a new gradient shader.
    material = c4d.BaseMaterial(c4d.Mmaterial)
    shader = c4d.BaseShader(c4d.Xgradient)
    
    # Get a copy of the c4d.Gradient data referenced by the gradient shader
    # and a copy of the knot data stored in the c4d.Gradient data. The knot
    # data is expressed as a c4d.BaseCoontainer.
    gradient = shader[c4d.SLA_GRADIENT_GRADIENT]
    knotData = gradient.GetData(c4d.GRADIENT_KNOT)
    
    # Iterate over all knots in the knot data container and set their 
    # interpolations to linear. Each knot in the knot data container is itself 
    # a c4d.BaseContainer, storing the data for a single knot.
    for _, knot in knotData:
        knot[c4d.GRADIENTKNOT_INTERPOLATION] = c4d.GRADIENT_INTERPOLATION_NONE

    # Items can also be retrieved by their index from a BaseContainer, here 
    # the first index, i.e., second item, in the container. In this case the 
    # position of the knot is written and then the knot container is being 
    # written back into the index its has been retrieved from.
    knot = knotData.GetIndexData(1)

    knot[c4d.GRADIENTKNOT_POSITION] = 0.5
    knotData.SetIndexData(1, knot)
    
    # After these modifications the knots must be written back into the 
    # c4d.Gradient data, because GetData() returned a copy above. This also
    # does apply to the shader and its gradient for the same reason.
    gradient.SetData(c4d.GRADIENT_KNOT, knotData)
    shader[c4d.SLA_GRADIENT_GRADIENT] = gradient
    
    # Aside from assigning the shader to the correct parameter of the 
    # material, it is also important to call BaseList2D.InsertShader(), as 
    # otherwise the setup will not work.
    material.InsertShader(shader)
    material[c4d.MATERIAL_COLOR_SHADER] = shader

    # Finally, the material is being inserted into the active document and an
    # update event is being pushed event to Cinema 4D, so that its GUI can 
    # catch up to our changes. 'doc' is a predefined module attribute in 
    # script manger scripts which points to the active document. It is
    # equivalent to c4d.documents.GetActiveDocument().
    doc.InsertMaterial(material)
    c4d.EventAdd()

if __name__=='__main__':
    main()

m_adam

Hi @danielsian, I we need to update this example and also the documentation about Gradient. Thanks for bringing that to our attention.
Gradient handling is now different and heavily rely on the maxon API via the GradientInterface. The old c4d.Gradient is now just a mirror of the GradientInterface.
Therefor all constants were moved to the maxon API. Find bellow the adapted example:

import c4d
import maxon

def main():
    # Create a new material and a new gradient shader.
    material = c4d.BaseMaterial(c4d.Mmaterial)
    shader = c4d.BaseShader(c4d.Xgradient)
    
    # Get a copy of the c4d.Gradient data referenced by the gradient shader
    # and a copy of the knot data stored in the c4d.Gradient data. The knot
    # data is expressed as a c4d.BaseCoontainer.
    gradient = shader[c4d.SLA_GRADIENT_GRADIENT]
    knotData = gradient.GetData(c4d.GRADIENT_KNOT)
    
    # Iterate over all knots in the knot data container and set their 
    # interpolations to linear. Each knot in the knot data container is itself 
    # a c4d.BaseContainer, storing the data for a single knot.
    for _, knot in knotData:
        knot[c4d.GRADIENTKNOT_INTERPOLATION] = maxon.GRADIENT_INTERPOLATION_TYPE.SMOOTHKNOT

    # Items can also be retrieved by their index from a BaseContainer, here 
    # the first index, i.e., second item, in the container. In this case the 
    # position of the knot is written and then the knot container is being 
    # written back into the index its has been retrieved from.
    knot = knotData.GetIndexData(1)

    knot[c4d.GRADIENTKNOT_POSITION] = 0.5
    knotData.SetIndexData(1, knot)
    
    # After these modifications the knots must be written back into the 
    # c4d.Gradient data, because GetData() returned a copy above. This also
    # does apply to the shader and its gradient for the same reason.
    gradient.SetData(c4d.GRADIENT_KNOT, knotData)
    shader[c4d.SLA_GRADIENT_GRADIENT] = gradient
    
    # Aside from assigning the shader to the correct parameter of the 
    # material, it is also important to call BaseList2D.InsertShader(), as 
    # otherwise the setup will not work.
    material.InsertShader(shader)
    material[c4d.MATERIAL_COLOR_SHADER] = shader

    # Finally, the material is being inserted into the active document and an
    # update event is being pushed event to Cinema 4D, so that its GUI can 
    # catch up to our changes. 'doc' is a predefined module attribute in 
    # script manger scripts which points to the active document. It is
    # equivalent to c4d.documents.GetActiveDocument().
    doc.InsertMaterial(material)
    c4d.EventAdd()

if __name__=='__main__':
    main()

For other values please take a look at the C++ documentation of GRADIENT_INTERPOLATION_TYPE.

Cheers,
Maxime.

m_adam

Hi @danielsian, I we need to update this example and also the documentation about Gradient. Thanks for bringing that to our attention.
Gradient handling is now different and heavily rely on the maxon API via the GradientInterface. The old c4d.Gradient is now just a mirror of the GradientInterface.
Therefor all constants were moved to the maxon API. Find bellow the adapted example:

import c4d
import maxon

def main():
    # Create a new material and a new gradient shader.
    material = c4d.BaseMaterial(c4d.Mmaterial)
    shader = c4d.BaseShader(c4d.Xgradient)
    
    # Get a copy of the c4d.Gradient data referenced by the gradient shader
    # and a copy of the knot data stored in the c4d.Gradient data. The knot
    # data is expressed as a c4d.BaseCoontainer.
    gradient = shader[c4d.SLA_GRADIENT_GRADIENT]
    knotData = gradient.GetData(c4d.GRADIENT_KNOT)
    
    # Iterate over all knots in the knot data container and set their 
    # interpolations to linear. Each knot in the knot data container is itself 
    # a c4d.BaseContainer, storing the data for a single knot.
    for _, knot in knotData:
        knot[c4d.GRADIENTKNOT_INTERPOLATION] = maxon.GRADIENT_INTERPOLATION_TYPE.SMOOTHKNOT

    # Items can also be retrieved by their index from a BaseContainer, here 
    # the first index, i.e., second item, in the container. In this case the 
    # position of the knot is written and then the knot container is being 
    # written back into the index its has been retrieved from.
    knot = knotData.GetIndexData(1)

    knot[c4d.GRADIENTKNOT_POSITION] = 0.5
    knotData.SetIndexData(1, knot)
    
    # After these modifications the knots must be written back into the 
    # c4d.Gradient data, because GetData() returned a copy above. This also
    # does apply to the shader and its gradient for the same reason.
    gradient.SetData(c4d.GRADIENT_KNOT, knotData)
    shader[c4d.SLA_GRADIENT_GRADIENT] = gradient
    
    # Aside from assigning the shader to the correct parameter of the 
    # material, it is also important to call BaseList2D.InsertShader(), as 
    # otherwise the setup will not work.
    material.InsertShader(shader)
    material[c4d.MATERIAL_COLOR_SHADER] = shader

    # Finally, the material is being inserted into the active document and an
    # update event is being pushed event to Cinema 4D, so that its GUI can 
    # catch up to our changes. 'doc' is a predefined module attribute in 
    # script manger scripts which points to the active document. It is
    # equivalent to c4d.documents.GetActiveDocument().
    doc.InsertMaterial(material)
    c4d.EventAdd()

if __name__=='__main__':
    main()

For other values please take a look at the C++ documentation of GRADIENT_INTERPOLATION_TYPE.

Cheers,
Maxime.

danielsian

@m_adam
Brilliant!
Thanks a lot!