Extract BSDF values from Blender in Python

extract-bsdf-values.py

import bpy
import colorsys
import json

# https://blender.stackexchange.com/a/80047/58635
def _convert_rgb_to_hsv(red, green, blue):
    return colorsys.rgb_to_hsv(*_linear_to_srgb(red, green, blue))

# https://blender.stackexchange.com/a/80047/58635
def _linear_to_srgb(r, g, b):
    def linear(c):
        a = .055
        if c <= .0031308:
            return 12.92 * c
        else:
            return (1+a) * c**(1/2.4) - a
    return tuple(linear(c) for c in (r, g, b))


def exportMaterials(obj=None):
    ''' find the material we want'''
    if obj:
        # list mats for selected objects
        for mat in obj.data.materials:
            if pbsdf != None:
                print("-------",mat.name,"-------")
                print(json.dumps(nodeToJSON(mat)))
                print("-------")
    else:
        # list all materials in scene
        for mat in bpy.data.materials:
            pbsdf = nodeToJSON(mat)
            if pbsdf != None:
                print("-------",mat.name,"-------")
                print(json.dumps(nodeToJSON(mat)))
                print("-------")


def nodeToJSON(mat):
    '''converts principled materials nodes to a set of list/dictionaries'''
    principledNodeCount = 0
    volumeNodeCount = 0
    pbsdf = {"Name": mat.name}
    
    for node in mat.node_tree.nodes:
        if node.type == 'BSDF_PRINCIPLED':
            principledNodeCount += 1
            base_color_rgb=[1,1,1]
            base_color_rgb[0] = node.inputs[0].default_value[0]
            base_color_rgb[1] = node.inputs[0].default_value[1]
            base_color_rgb[2] = node.inputs[0].default_value[2]
            pbsdf["BaseColorHue"], pbsdf["BaseColorSaturation"], pbsdf["BaseColorValue"] = _convert_rgb_to_hsv(*base_color_rgb)
            pbsdf["BaseColorAlpha"] = node.inputs[0].default_value[3]
            pbsdf["Subsurface"] = node.inputs[1].default_value
            pbsdf["SubsurfaceRadiusX"] = node.inputs[2].default_value[0]
            pbsdf["SubsurfaceRadiusY"] = node.inputs[2].default_value[1]
            pbsdf["SubsurfaceRadiusZ"] = node.inputs[2].default_value[2]
            subsurface_color_rgb = [1,1,1] 
            subsurface_color_rgb[0] = node.inputs[3].default_value[0]
            subsurface_color_rgb[1] = node.inputs[3].default_value[1]
            subsurface_color_rgb[2] = node.inputs[3].default_value[2]
            pbsdf["SubsurfaceColorHue"], pbsdf["SubsurfaceColorSaturation"], pbsdf["SubsurfaceColorValue"] = _convert_rgb_to_hsv(*subsurface_color_rgb)
            pbsdf["SubsurfaceColorAlpha"] = node.inputs[3].default_value[3]
            pbsdf["Metallic"] = node.inputs[4].default_value
            pbsdf["Specular"] = node.inputs[5].default_value
            pbsdf["SpecularTint"] = node.inputs[6].default_value
            pbsdf["Roughness"] = node.inputs[7].default_value
            pbsdf["Anisotropic"] = node.inputs[8].default_value
            pbsdf["AnisotropicRotation"] = node.inputs[9].default_value
            pbsdf["Sheen"] = node.inputs[10].default_value
            pbsdf["SheenTint"] = node.inputs[11].default_value
            pbsdf["Clearcoat"]= node.inputs[12].default_value
            pbsdf["ClearcoatRoughness"] = node.inputs[13].default_value
            pbsdf["IndexOfRefraction"] = node.inputs[14].default_value
            pbsdf["Transmission"] = node.inputs[15].default_value
        elif node.type == 'CUSTOM' and node.name == 'Principled Volume':
            volumeNodeCount += 1
            pbsdf['HasPBSDFVolume'] = "true"
            vol_color_rgb = [1,1,1]
            vol_color_rgb[0] = node.inputs[0].default_value[0]
            vol_color_rgb[1] = node.inputs[0].default_value[1]
            vol_color_rgb[2] = node.inputs[0].default_value[2]
            pbsdf["VolumeColorHue"], pbsdf["VolumeColorSaturation"], pbsdf["VolumeColorValue"] = _convert_rgb_to_hsv(*vol_color_rgb)
            pbsdf["VolumeColorAlpha"] = node.inputs[0].default_value[3]
            pbsdf["VolumeDensity"] = node.inputs[2].default_value
            pbsdf["VolumeAnisotropy"] = node.inputs[4].default_value
            vol_absorb_rgb = [1,1,1]
            vol_absorb_rgb[0] = node.inputs[5].default_value[0]
            vol_absorb_rgb[1] = node.inputs[5].default_value[1]
            vol_absorb_rgb[2] = node.inputs[5].default_value[2]
            pbsdf["VolumeAbsorptionColorHue"], pbsdf["VolumeAbsorptionColorSaturation"], pbsdf["VolumeAbsorptionColorValue"] = _convert_rgb_to_hsv(*vol_absorb_rgb)
            pbsdf["VolumeAbsorptionColorAlpha"] = node.inputs[5].default_value[3]
            pbsdf["VolumeEmissionStrength"] = node.inputs[6].default_value
            vol_emiss_rgb = [1,1,1]
            vol_emiss_rgb[0] = node.inputs[7].default_value[0]
            vol_emiss_rgb[1] = node.inputs[7].default_value[1]
            vol_emiss_rgb[2] = node.inputs[7].default_value[2]
            pbsdf["VolumeEmissionColorHue"], pbsdf["VolumeEmissionColorSaturation"], pbsdf["VolumeEmissionColorValue"] = _convert_rgb_to_hsv(*vol_emiss_rgb)
            pbsdf["VolumeEmissionColorAlpha"] = node.inputs[7].default_value[3]
            pbsdf["VolumeBlackbodyIntensity"] = node.inputs[8].default_value
            vol_bbtint_rgb = [1,1,1]
            vol_bbtint_rgb[0] = node.inputs[9].default_value[0]
            vol_bbtint_rgb[1] = node.inputs[9].default_value[1]
            vol_bbtint_rgb[2] = node.inputs[9].default_value[2]
            pbsdf["VolumeBlackbodyTintHue"], pbsdf["VolumeBlackbodyTintSaturation"], pbsdf["VolumeBlackbodyTintValue"] = _convert_rgb_to_hsv(*vol_bbtint_rgb)
            pbsdf["VolumeBlackbodyTintAlpha"] = node.inputs[9].default_value[3]
            pbsdf["VolumeTemperature"] = node.inputs[10].default_value
            
            
    if principledNodeCount > 1:
        print("Warning: More than one principled Node for material", mat.name)

    if volumeNodeCount > 1:
        print("Warning: More than one volume Node for material", mat.name)
    
    if principledNodeCount == 0:
        return None
    
    return pbsdf
    

# test code
# exportMaterials(bpy.context.active_object)      # exports material(s) for active obj
exportMaterials()                               # exports materials for entire scene