geo-ambient-occlusion

geo-ambient-occlusion

Generates a per-vertex ambient occlusion array for arbitrary meshes.

Demo

Support notes

• Requires the OES_texture_float extension.
• Currently unsupported by Safari.

How does it work?

geo-ambient-occlusion renders multiple shadow maps for your mesh from random viewpoints. It averages the occlusion for each vertex across all the shadow maps to calculate an ambient occlusion value for each. This data is converted into a Float32Array of occlusion values and returned to you for immediate use as an attribute in your shader program.

geo-ambient-occlusion is built on top of the disgustingly good regl WebGL library.

Install

npm install geo-ambient-occlusion

Example

let dragon = require('stanford-dragon/2');
const geoao = require('geo-ambient-occlusion');

const aoSampler = geoao(dragon.positions, { cells: dragon.cells });

for (let i = 0; i < 256; i++) {
  aoSampler.sample();
}

const ao = aoSampler.report();

aoSampler.dispose();

API

const geoao = require('geo-ambient-occlusion')

Constructor

const aoSampler = geoao(positions[, opts])

positions is the vertex array for your mesh. It can be any of:

• Flat array [1,2,3,4,5,6]
• Array of arrays [[1,2,3], [4,5,6]]
• Array of TypedArrays [new Float32Array([1,2,3]), new Float32Array([4,5,6])]
• TypedArray new Float32Array([1,2,3,4,5,6])
• ndarray ndarray(new Float32Array([1,2,3,4,5,6]))

opts is an object that can have the following properties:

• resolution (int) is the resolution to build the depth buffer at. Defaults to 512.
• bias (float) is the bias applied to the shadow map while building the ambient occlusion data. Defaults to 0.01.
• cells is the index data for your mesh, if you're using a simplicial complex. Defaults to undefined.
• normals are per-vertex normals, either in an array or array of arrays. If not supplied, they will be computed using the normals npm module.
• regl is an optional regl context you can provide to reduced the overhead of multiple WebGL contexts. This context will need to have the OES_texture_float extension enabled, and depending on the size of your mesh, also the OES_element_index_uint extension.

Methods

aoSampler.sample()

Collects a single sample of ambient occlusion data. Run this several hundred times to reach a useful average.

const ao = aoSampler.report()

Returns the average ambient occlusion, per vertex, sampled so far. Format is a Float32Array.

aoSampler.dispose()

Disposes of all resources used for this sampling. Does not dispose of the internal regl context if it was provided by the user. Behavior of aoSampler after calling this function is undefined.