gl-util

Set of practical functions for webgl.

const u = require('gl-util');

let gl = u.context(canvas)

let prog = u.program(gl, `
	precision mediump float;

	attribute vec2 position;

	void main() {
		gl_Position = vec4(position * 2. - 1., 0, 1);
	}
`, `
	precision mediump float;

	uniform vec4 color;

	void main () {
		gl_FragColor = color;
	}
`);
u.attribute(prog, 'position', [0,0, 1,0, 0,1]);
u.uniform(prog, 'color', [1, .2, 0, 1.]);

gl.drawArrays(gl.TRIANGLES, 0, 3);

API

context(container|canvas|options?)

Create and/or return WebGL context for the canvas element, possibly based on options. If container is not defined, document.body is used.

| Option | Meaning | |---|---| | canvas | A canvas element to obtain context for. | | container | An element to create canvas in and return context for it. | | width | If specified, will set the canvas width. | | height | If specified, will set the canvas height. | | pixelRatio | Multiplier for width and height. | | attributes | Attributes object. Available attributes: alpha, depth, stencil, antialias, premultipliedAlpha, preserveDrawingBuffer and failIfMajorPerformanceCaveat. |

const getContext = require('gl-util/context')

// create canvas element in the document.body and retrieve context for it
let gl = getContext({
	attributes: {
		antialias: true
	}
})

prog = program(gl, prog|vert?, frag?)

Set active program or create a new program from vertex and fragment sources. Programs are cached for the context by source. The WebGLProgram instance is returned.

const program = require('gl-util/program')

// create and set program
let prog = program(gl, `
	precision mediump float;

	attribute vec2 position;

	void main() {
		gl_Position = vec4(position * 2. - 1., 0, 1);
	}
`, `
	precision mediump float;

	uniform sampler2D image;
	uniform vec2 shape;
	uniform float x;

	void main () {
		gl_FragColor = texture2D(image, gl_FragCoord.xy / shape);
	}
`)

// set active program
program(gl, prog)

unif = uniform(gl|program, {name: data, ...} | name?, data?)

Get/set uniform or multiple uniforms. Returns an object with uniform parameters: {name, location, data, type}. Uniforms are stored per-program instance.

const uniform = require('gl-util/uniform')

uniform(gl, 'color', [1, .2, 0, 1]);

txt = texture(gl, {name: params, ...} | name?, params?)

Set texture[s] data or parameters:

| Name | Meaning | |---|---| | data | Data passed to texture. Can be array, typed array, image, canvas or string denoting the URL of image to load. | | index | Texture unit number, if undefined - calculated automatically. | | filter | Sets texture scaling for both min and mag. Can be defined as two separate properties minFilter and magFilter. By default gl.LINEAR. | | wrap | Defines texture tiling vertically and horizontally. Can be defined precisely as wrapS and wrapT. By default gl.CLAMP_TO_EDGE, can be gl.MIRRORED_REPEAT or gl.. | | width | In pixels | | height | In pixels | | format | gl.ALPHA, gl.RGB, gl.RGBA (default), gl.LUMINANCE, gl.LUMINANCE_ALPHA, gl.DEPTH_COMPONENT, gl.DEPTH_STENCIL, etc | | type | gl.UNSIGNED_BYTE, can be gl.FLOAT with proper extension enabled | | level | 0, mipmap level. |

Returns object with texture properties {data, index, location, minFilter, magFilter, wrapS, wrapT, width, height, format, type, texture}.

const texture = require('gl-util/texture')

let {width, height} = texture(gl, 'image', './picture.gif');

attr = attribute(gl, {name: params, ...} | name?, params?)

Set attribute[s] data or parameters:

| Name | Default | Meaning | |---|---|---| | data | null | Data for the attribute, can be array, typed array or array buffer | | size | 2 | Number of data items per vertex | | stride | 0 | Offset in bytes between the beginning of consecutive vertex attributes. | | offset | 0 | Offset in bytes of the first component in the data. Must be a multiple of type. | | type | gl.FLOAT | Data type of each component in the data array. Must be one of: gl.BYTE, gl.UNSIGNED_BYTE, gl.SHORT, gl.UNSIGNED_SHORT, gl.FLOAT. | | usage | gl.STATIC_DRAW | Mode of draw: gl.STATIC_DRAW (rare changes), gl.DYNAMIC_DRAW (frequent changes) or gl.STREAM_DRAW (frequent updates) | | normalized | false | If fixed-point data values should be normalized or are to converted to fixed point values when accessed. | | index | 0 | Attribute unit number, detected automatically if omitted. | | target | gl.ARRAY_BUFFER | | | buffer | null | WebGLBuffer to use for attribute |

Returns attribute properties {data, size, stride, offset, usage, type, normalized, index, target, buffer}.

const attribute = require('gl-util/attribute')

attribute(gl, 'position', [0,0,1,0,0,1]);

clear(gl, optsion?)

Clear the viewport.

Motivation

There are regl, stack.gl and many other WegGL components or frameworks, so why gl-util?

• WebGL frameworks API is usually difficult to remember, not much better than pure WebGL, although regl does a great job. gl-util is like functions from any WebGL tutorial - tiny, handy and already familiar.
• gl-util does not supersede WebGL API - that allows for debugging pure WebGL at any moment.
• gl-util is tiny - if one needs minimalistic WebGL setup it may be better to opt for a couple of functions than massive stack.gl components or regl (70kb+).
• regl API may be cumbersome for organizing components

License

(c) 2018 Dmitry Yv. MIT License

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