/// Authors USD Shader inputs onto the given shader and material and connects private shader
/// inputs to the public material inputs (the intent being, inputs are authored on the material
/// and flow into the shader, which is a detail of the network).
static void CreateShaderInputs <T>(pxr.UsdShadeShader shader,
pxr.UsdShadeMaterial material,
Dictionary <string, T> paramDict)
{
USD.NET.UsdTypeBinding binding;
if (!USD.NET.UsdIo.Bindings.GetBinding(typeof(T), out binding))
{
// TODO: add "with exception" to GetBinding().
throw new Exception("Type not found: " + typeof(T).Name);
}
foreach (var kvp in paramDict)
{
var inputName = new pxr.TfToken(kvp.Key);
var matInput = material.CreateInput(inputName, binding.sdfTypeName);
var shaderInput = shader.CreateInput(inputName, binding.sdfTypeName);
matInput.Set(binding.toVtValue(kvp.Value));
shaderInput.Set(binding.toVtValue(kvp.Value));
shaderInput.ConnectToSource(matInput);
}
}
/// Authors a USD Material, Shader, parameters and connections between the two.
/// The USD shader structure consists of a Material, which is connected to a shader output. The
/// Shader consists of input parameters which are either connected to other shaders or in the case
/// of public parameters, back to the material which is the public interface for the shading
/// network.
///
/// This function creates a material, shader, inputs, outputs, zero or more textures, and for each
/// texture, a single primvar reader node to read the UV data from the geometric primitive.
static string CreateMaterialNetwork(USD.NET.Scene scene,
IExportableMaterial material,
string rootPath = null)
{
var matSample = new ExportMaterialSample();
// Used scene object paths.
string materialPath = GetMaterialPath(material, rootPath);
string shaderPath = GetShaderPath(material, materialPath);
string displayColorPrimvarReaderPath = GetPrimvarPath(material, "displayColor", shaderPath);
string displayOpacityPrimvarReaderPath = GetPrimvarPath(material, "displayOpacity", shaderPath);
// The material was already created.
if (scene.GetPrimAtPath(materialPath) != null)
{
return(materialPath);
}
// Ensure the root material path is defined in the scene.
scene.Stage.DefinePrim(new pxr.SdfPath(rootPath));
// Connect the materail surface to the output of the shader.
matSample.surface.SetConnectedPath(shaderPath, "outputs:result");
scene.Write(materialPath, matSample);
// Create the shader and conditionally connect the diffuse color to the MainTex output.
var shaderSample = GetShaderSample(material);
var texturePath = CreateAlphaTexture(scene, shaderPath, material);
if (texturePath != null)
{
// A texture was created, so connect the opacity input to the texture output.
shaderSample.opacity.SetConnectedPath(texturePath, "outputs:a");
}
else
{
// TODO: currently primvars:displayOpacity is not multiplied when an alpha texture is
// present. However, this only affects the USD preview. The correct solution
// requires a multiply node in the shader graph, but this does not yet exist.
scene.Write(displayOpacityPrimvarReaderPath, new PrimvarReader1fSample("displayOpacity"));
shaderSample.opacity.SetConnectedPath(displayOpacityPrimvarReaderPath, "outputs:result");
}
// Create a primvar reader to read primvars:displayColor.
scene.Write(displayColorPrimvarReaderPath, new PrimvarReader3fSample("displayColor"));
// Connect the diffuse color to the primvar reader.
shaderSample.diffuseColor.SetConnectedPath(displayColorPrimvarReaderPath, "outputs:result");
scene.Write(shaderPath, shaderSample);
//
// Everything below is ad-hoc data, which is written using the low level USD API.
// It consists of the Unity shader parameters and the non-exported texture URIs.
// Also note that scene.GetPrimAtPath will return null when the prim is InValid,
// so there is no need to call IsValid() on the resulting prim.
//
var shadeMaterial = new pxr.UsdShadeMaterial(scene.GetPrimAtPath(materialPath));
var shadeShader = new pxr.UsdShadeShader(scene.GetPrimAtPath(shaderPath));
if (material.SupportsDetailedMaterialInfo)
{
CreateShaderInputs(shadeShader, shadeMaterial, material.FloatParams);
CreateShaderInputs(shadeShader, shadeMaterial, material.ColorParams);
CreateShaderInputs(shadeShader, shadeMaterial, material.VectorParams);
}
CreateTextureUris(shadeShader.GetPrim(), material);
return(materialPath);
}
