geom-builder

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


Installation

``bash
npm install geom-builder
`

Usage

`js
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

$3

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]).

$3

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

$3

- pos: vec3 - position to add

_Note: adding a vertex position will increment builder.count counter indicating number of vertices added so far_

$3

- normal: vec3 - normal to add

_Note: you need to enable normals in constructor_

$3

- uv: vec2 - uv texture coord to add

_Note: you need to enable uvs in constructor_

$3

- vertexColor: vec4 - vertexColor to add

_Note: you need to enable vertexColors in constructor_

$3

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

_Note: you need to enable cells in constructor_

$3

- 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.