geom-builder

Simplicial-complex-like geometry builder backed by typed arrays.

Installation

npm install geom-builder

Usage

import createGeomBuilder from "geom-builder";
const builder = createGeomBuilder({ colors: 4, cells: 3 });

builder.addPosition([0, 0, 0]);
builder.addPosition([1, 0, 0]);
builder.addPosition([1, 1, 0]);

builder.addColor([1, 0, 0, 1]);
builder.addColor([0, 1, 0, 1]);
builder.addColor([0, 0, 1, 1]);

builder.addCell([0, 1, 0]);
// or builder.addCell(0, 1, 0)

//builder.count = 3 //vertex count
//builder.indexCount = 3 //indices count
//builder.positions = Float32Array(0, 0, 0, 1, 0, 0, 1, 1, 0, ..,)
//builder.colors = Float32Array(1, 0, 0, 1, 0, 1, 0, 1, 0, 0, 1, 1, ...)
//builder.cells = Uint16Array(0, 1, 2, ...)

API

GeomBuilder

var createGeomBuilder = require("geom-builder");

builder = createGeomBuilder(opts)

Create new geometry builder. Each attribute can be enabledby passing an integer number e.g.: createGeomBuilder({ positions: 3, colors: 4, cells: 2 }) for colored lines.

• opts
  • size : Int - preallocated vertex buffer size, 32
  • positions : Int - enable positions attribute, 3
  • colors : Int - enable colors attribute
  • normals : Int - enable normals attribute
  • uvs : Int - enable uvs attribute
  • cells : Int - enable cells (indices)

Note: positions attribute is always enabled and defaults to size 3

Adding vertex and index data

Every time we add vertex position, color etc internal buffer size is checked and expanded by doubling its capacity as necessary. Therefore builder.count should be used to determine how many vertices to draw instead of builder.positions.length as not all allocated vertex has to be used. Similarly for meshes with cells builder.indexCount should be used instead of builder.cells.length.

All enabled attributes can be accessed by builder.attribName e.g.: builder.colors.

All data methods accept structs or individual components. E.g. builder.addPosition(v) and builder.addPosition(v[0], v[1], v[2]).

builder.reset()

Reset all the counters to prepare arrays for reuse. Nothing is deallocated.

builder.addPosition(pos)

• pos : vec3 - position to add

Note: adding a vertex position will increment builder.count counter indicanting number of vertices added so far

builder.addColor(color)

• color : vec4 - color to add

Note: you need to enable colors in constructor

builder.addNormal(normal)

• normal : vec3 - normal to add

Note: you need to enable normals in constructor

builder.addUV(uv)

• uv : vec2 - uv texture coord to add

Note: you need to enable uvs in constructor

builder.addCell(cell)

• cell : number, vec2, vec3 - cell (face) with vertex indices to add

Note: you need to enable cells in constructor

License

MIT, see LICENSE.md for details.