geom-builder

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({ vertexColors: 4, cells: 3 });

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

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

createGeomBuilder(opts): geometryBuilder

Parameters

• opts
  • size: Int (default: 32) - preallocated vertex buffer size
  • positions: Int (default: 3) - positions attribute
  • normals: Int - enable normals attribute
  • uvs: Int - enable uvs attribute
  • vertexColors: Int - enable vertexColors attribute
  • cells: Int - enable cells (indices)
  • attributeNames: Int - enable an arbitrary attribute

Note: positions attribute is always enabled and defaults to size 3 Note: attribute names should be plural

Returns

geometryBuilder: { positions: Float32Array, vertexColors: Float32Array, cells: Uint32Array }: each attribute can be enabled by passing an integer e.g.: createGeomBuilder({ positions: 3, vertexColors: 4, cells: 2 }).

Adding vertex and index data

Every time we add vertex position, color, etc., the 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 vertices have to be used. Similarly for meshes with cells builder.cellsIndex should be used instead of builder.cells.length.

All enabled attributes can be accessed by builder.attributeName e.g. builder.vertexColors.

All data methods accept structs or individual components e.g. builder.addPosition(v) or 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 indicating number of vertices added so far

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.addVertexColor(color)

• vertexColor: vec4 - vertexColor to add

Note: you need to enable vertexColors in constructor

builder.addCell(cell)

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

Note: you need to enable cells in constructor

builder.addAttributeName(attributeValue)

• attributeValue: number | array - any attribute to add

Note: you need to enable attributeNames (plural) in constructor to get builder.addAttributeName (singular)

License

MIT, see LICENSE.md for details.