Draft enum, describing different methods for computing vertex counts.

vertex-count-method.ts

/**
 * Various methods of estimating a vertex count. For some background on why
 * multiple definitions of a vertex count should exist, see [_Vertex Count
 * Higher in Engine than in 3D Software_](https://shahriyarshahrabi.medium.com/vertex-count-higher-in-engine-than-in-3d-software-badc348ada66).
 *
 * NOTICE: Many rendering features, such as volumetric transmission, may lead
 * to additional passes over some or all vertices. Such tradeoffs are
 * implementation-dependent, and not considered here.
 */
export enum VertexCountMethod {
	/**
	 * Expected number of vertices processed by the vertex shader for one render
	 * pass, without considering the vertex cache.
	 */
	RENDER = 'render',
	/**
	 * Expected number of vertices proceessed by the vertex shader for one render
	 * pass, assuming a 100% hit ratio on the vertex cache. Assumes vertex attributes
	 * have been optimized for locality of reused references (see {@link reorder}).
	 * Typical GPU vertex caches are small, holding 16-32 vertices, and rarely
	 * achieve 100% hit ratios in practice.
	 */
	RENDER_OPTIMISTIC = 'render-optimistic',
	/**
	 * Expected number of vertices uploaded to the GPU, assuming that a client
	 * uploads each unique {@link Primitive} individually, potentially duplicating
	 * reused vertex attributes {@link Accessor Accessors}, but never duplicating
	 * reused {@link Mesh Meshes} or {@link Primitive Primitives} in GPU memory.
	 */
	UPLOAD = 'upload',
	/**
	 * Expected number of vertices uploaded to the GPU, assuming that a client
	 * uploads each unique {@link Accessor} only once. Unless glTF vertex
	 * attributes are pre-processed to a known buffer layout, and the client is
	 * optimized for that buffer layout, this total will be optimistic.
	 */
	UPLOAD_OPTIMISTIC = 'upload-optimistic',
	/**
	 * Total number of unique vertices represented, considering all attributes of
	 * each vertex, and removing any duplicates.
	 *
	 * NOTE: Has no direct relationship to runtime characteristics, but may be
	 * helpful in identifying asset optimization opportunities.
	 */
	DISTINCT = 'distinct',
	/**
	 * Total number of unique vertices represented, considering aonly vertex
	 * positions, and removing any duplicates.
	 *
	 * NOTE: Has no direct relationship to runtime characteristics, but may be
	 * helpful in identifying asset optimization opportunities.
	 */
	DISTINCT_POSITION = 'distinct-position',
	/**
	 * Number of vertex positions never used by any mesh primitive.
	 *
	 * NOTE: Has no direct relationship to runtime characteristics, but may be
	 * helpful in identifying asset optimization opportunities.
	 */
	UNUSED = 'unused',
}