Unable to Turn off Shading

[JonahWeinbaum]

I would like to turn off mesh shading entirely and I have tried setting all relevant shadow and shading settings to false and it has absolutely no effect on the inherent shading of the mesh.

I've tried everything from removing surface normals to changing materials (this works but then I don't have per vertex coloring). It seems like it is calculating normals and doing surface shading and there is no way to turn it off.

[brentyi]

Sorry for the delay here! I think we could add a material="unlit" to helpers like add_mesh_simple(). Open to PRs for this!

In the meantime, I asked Claude and it gave me this very roundabout way:

import viser


def get_unlit_box() -> bytes:
    import trimesh
    from trimesh.exchange.gltf import export_glb

    mesh = trimesh.creation.box()
    mesh.visual.material = trimesh.visual.material.PBRMaterial(
        baseColorFactor=[0.5, 0.8, 0.0, 1.0]
    )

    # Create a scene.
    scene = trimesh.Scene(geometry=mesh)

    # Define the postprocessor function to add KHR_materials_unlit.
    def add_unlit(gltf_tree):
        """Post-process the GLTF tree to add KHR_materials_unlit extension."""
        if "materials" not in gltf_tree:
            return

        # Modify materials to include the KHR_materials_unlit extension.
        for material_dict in gltf_tree["materials"]:
            material_dict["extensions"] = {"KHR_materials_unlit": {}}

        # Register the extension.
        gltf_tree["extensionsUsed"] = gltf_tree.get("extensionsUsed", []) + [
            "KHR_materials_unlit"
        ]

    # Export with the postprocessor.
    return export_glb(scene, tree_postprocessor=add_unlit)


# Show mesh as GLB.
server = viser.ViserServer(verbose=False)
box = server.scene.add_glb("/box", get_unlit_box())
server.sleep_forever()