ANARI material library support

VTK now offers material library support for ANARI rendering through a shared vtkRenderMaterialLibrary base class in RenderingCore. This replaces renderer-specific implementations with a unified framework that works across ANARI, OSPRay, and future backends. The two backends currently implemented are vtkOSPRayMaterialLibrary and vtkANARIMaterialLibrary.

Texture I/O is now handled with a common ReadTextureFileOrData interface, to allow each backend to do its parameter validation and serialization.

The ANARI implementation includes case-insensitive parameter lookups and a MATERIAL_NAMES macro for runtime introspection, making it easier to work with materials programmatically.

Here’s how you define materials for ANARI in a material file:

newmtl glossy_red
ka 0.1 0.1 0.1
kd 0.8 0.0 0.0
ks 0.9 0.9 0.9
ns 128.0
map_kd red_texture.png

newmtl matte_blue
ka 0.05 0.05 0.05
kd 0.0 0.0 0.8
ks 0.1 0.1 0.1
ns 8.0

Then load and use the material library with the ANARI renderer:

from vtkmodules.vtkRenderingAnari import vtkANARIMaterialLibrary, vtkAnariPass, vtkAnariSceneGraph
from vtkmodules.vtkRenderingCore import vtkRenderer

material_lib = vtkANARIMaterialLibrary()
material_lib.ImportMaterials("materials.mtl")

vtkAnariSceneGraph.SetMaterialLibrary(material_lib, renderer)

renderer = vtkRenderer()
anari_pass = vtkAnariPass()
renderer.SetPass(anari_pass)

Or in C++:

auto material_lib = vtkNew<vtkANARIMaterialLibrary>();
material_lib->ImportMaterials("materials.mtl");

vtkAnariSceneGraph::SetMaterialLibrary(material_lib, renderer);

auto renderer = vtkNew<vtkRenderer>();
auto anari_pass = vtkNew<vtkAnariPass>();
renderer->SetPass(anari_pass);