s2maps-gpu/dist/gpu/context/buildMask.js

S2 Maps GPU - An open source, high-performance, and GPU-accelerated map engine for rendering large-scale, interactive maps.

/**
 * Builds a mask source
 * @param division - number of division to slice the geometry by
 * @param context - The current rendering context
 * @returns The mask source
 */
export default function buildMask(division, context) {
    const vertices = [];
    const indices = [];
    // prep variables
    const indexLength = division + 1;
    let t, s, indexAbove;
    let index = 0;
    // now we can build out the vertices and indices
    // vertices
    for (let j = 0; j <= division; j++) {
        t = (1 / division) * j;
        for (let i = 0; i <= division; i++) {
            s = (1 / division) * i;
            vertices.push(s, t);
        }
    }
    // indices
    for (let j = 0; j < division; j++) {
        // add degenerate if j is not 0
        if (j !== 0)
            indices.push((j + 1) * indexLength);
        for (let i = 0; i <= division; i++) {
            index = j * indexLength + i;
            indexAbove = (j + 1) * indexLength + i;
            indices.push(indexAbove, index);
        }
        // upon finishing a row, add a degenerate
        indices.push(index);
    }
    // return the mask
    const maskSource = {
        type: 'mask',
        vertexBuffer: context.buildGPUBuffer('mask vertex buffer', new Float32Array(vertices), GPUBufferUsage.VERTEX),
        indexBuffer: context.buildGPUBuffer('mask index buffer', new Uint32Array(indices), GPUBufferUsage.INDEX),
        codeTypeBuffer: context.buildGPUBuffer('mask code type buffer', new Uint32Array([0]), GPUBufferUsage.VERTEX),
        count: indices.length,
        offset: 0,
    };
    return maskSource;
}