How to create and change the color of a Node based material with a script

Question

I want to do an animation of a blender object which changes the color over time, in dependence of the temperature. Therefore zeffi already wrote a script which transforms different colormaps into blender. (Set color of Blender object based on external data (e. g. temperature) using a colormap)

Now I would like to create a node based material with a script, set the colormap to jet and when the temperature changes, I would like to change also the color.

Can someone post a little piece of script, how I can achieve this?

Thanks

Answer 1

I can answer one of your questions but you will need to download and install the add-on again if you haven't yet. The add-on now lets you access functionality via the script shown below.

• This assumes a recent version of the octave_gradients add-on is available locally.

code for using the add-on inside a script:

import bpy
import addon_utils

addon_utils.enable("octave_gradients")

# add material, or reuse existing one
mymat = bpy.data.materials.get('lazy_cube')
if not mymat:
    mymat = bpy.data.materials.new('lazy_cube')
    mymat.use_nodes = True

nodes = mymat.node_tree.nodes

if not 'ColorRamp' in nodes:
    nodes.new(type="ShaderNodeValToRGB")    
ColorRamp = nodes['ColorRamp']

# reuse the Octave Gradient maker code, when calling from this context, 
# it will add a function called 'external_octave' to the driver_namespace
# this function doesn't care what context you are in, all it wants
# is a reference to the ColorRamp node, and a number between 0..13
bpy.ops.scene.gradient_pusher()
external_octave = bpy.app.driver_namespace['external_octave']

# force ramp theme
external_octave(ColorRamp, 12)  # jet=12

# hook the ColorRamp up to the DiffuseBSDF node.
DiffuseBSDF = nodes.get("Diffuse BSDF")
mymat.node_tree.links.new(ColorRamp.outputs[0], DiffuseBSDF.inputs[0])

What you should be able to solve on your own is how to get temperatures into a range of 0 to 1, so the color ramp can map them.

Answer 2

Not that this is necessarily the answer you want, but it's very easy to change colors using vert colors (can be changed in a script very easily). In your noodle you can use vert colors to change what texture is shown. You could also probably have a material that uses alpha and lets the vert color show through your texture. Guessing.