gl-util

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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