IndexedFaceSet

IndexedFaceSet is a node type used in VRML 97 and X3D to represent a polygonal mesh by indexing into a set of vertices. The geometry is defined primarily by the coord field, a list of 3D points, and the coordIndex field, a sequence of integers that reference those points to form one or more polygonal faces. Faces are listed in order and terminated with -1; a face with N vertices uses N consecutive indices followed by -1. The front face orientation is determined by the ccw field; when ccw is true (the default), the vertices are ordered counterclockwise as seen from the front to define front-facing polygons.

Normals, colors and texture coordinates can be supplied in separate fields (normal and normalIndex, color and colorIndex, texCoord and texCoordIndex). If per-vertex attributes are used, normalPerVertex and colorPerVertex control whether the attribute applies per vertex or per face. If index arrays for those attributes are omitted, their data is assumed to align with the coordinate indices.

The creaseAngle field controls smoothing between adjacent faces when normals are per-vertex and matching normals are not provided; higher values produce smoother shading across edges.

The solid field indicates whether the shape is treated as a solid object, influencing rendering and applications that perform ray casting or culling; the default is true.

IndexedFaceSet is used to model a wide range of meshes, from simple convex shapes to complex concave surfaces. It is compatible with standard shading, texturing, and color per vertex. In practice, many implementations triangulate polygonal faces internally, and tools may convert IFS data to explicit triangle meshes for rendering.