Davidster / normal_pack

Compresses normal vectors (or any 3D unit vector) using Octahedron encoding

Compresses normal vectors (or any 3D unit vector) using Octahedron encoding.

This lossy compression scheme is able to achieve a compression ratio as high as 6:1 with an average error rate of less than 1 degree, depending on which representation is chosen.

Example:

let normal = [-0.5082557, 0.54751796, 0.6647558];

let encoded = normal_pack::EncodedUnitVector3U8::encode(normal);
let decoded = encoded.decode();

assert_eq!(decoded, [-0.52032965, 0.5473598, 0.6554802]);

Why compress my normals?

It is common for 3D renderers to be bottlenecked by memory bandwidth, such as when loading normals from VRAM for high-poly meshes to supply to your vertex shader. A smaller memory footprint for your normals corresponds to memory bandwidth savings and higher FPS in such scenarios.

How bad is 1 degree of error?

The teapot example generates a reference visual and contains the wgsl code required to decode the vector in a shader.

Standard [f32; 3] representation

Packed into a [u8; 2]

As a video

normal_pack_error.mp4

The skybox used in the example is the work of Emil Persson, aka Humus. http://www.humus.name