Control mesh appearance

This page explains how Mesh3D and Asset3D are shaded, and which settings you can change.

Lighting

The 3D view uses simple, fixed lighting: two directional lights and some ambient light. You cannot add lights, move them, or turn on shadows. There are no material properties, such as roughness, metallic surfaces, or specular highlights. See missing features.

Why does my mesh look flat or unlit?

Lighting needs vertex normals.

• Mesh3D without vertex_normals is drawn unlit: every triangle gets its plain color, so the shape is hard to see. Pass vertex_normals to get shading.
• Asset3D computes flat normals for meshes in the file that have none. To draw an asset unlit, give it all-zero vertex normals.

To compute smooth vertex normals for a Mesh3D yourself, you can use a library such as trimesh:

import trimesh

mesh = trimesh.load("model.obj", force="mesh")
rr.log(
    "mesh",
    rr.Mesh3D(
        vertex_positions=mesh.vertices,
        triangle_indices=mesh.faces,
        vertex_normals=mesh.vertex_normals,
    ),
)

Colors and textures

• vertex_colors: one color per vertex.
• albedo_factor: one color for the whole mesh. It is multiplied with the vertex colors and the texture.
• albedo_texture together with vertex_texcoords: a texture image.

See the Mesh3D reference for an example of a textured mesh. For Asset3D, colors and textures come from the file, and you can tint the whole asset with albedo_factor.

Transparency

The only way to make a mesh transparent is the alpha channel of albedo_factor:

rr.log("mesh", rr.Mesh3D(vertex_positions=positions, triangle_indices=triangles, albedo_factor=[255, 255, 255, 128]))

The alpha channel of vertex_colors and of the texture is ignored.

Front and back faces

By default, both sides of each triangle are drawn. Set face_rendering to "Front" or "Back" to draw only one side. Front faces have their vertices in counter-clockwise order.

rr.Mesh3D(vertex_positions=positions, triangle_indices=triangles, face_rendering="Front")