Last active
April 2, 2019 17:41
-
-
Save robertleeplummerjr/04d1529604d4d600dc4a432ebf98e93c to your computer and use it in GitHub Desktop.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
<html> | |
<body> | |
<canvas></canvas> | |
</body> | |
<script> | |
const canvas = document.querySelector('canvas'); | |
const gl = canvas.getContext('webgl2', { | |
alpha: false, | |
depth: false, | |
antialias: false | |
}); | |
const buffer = gl.createBuffer(); | |
gl.bindBuffer(gl.ARRAY_BUFFER, buffer); | |
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([1,1,-1,1,-1,-1,1,1,-1,-1,1,-1]), gl.STATIC_DRAW); | |
gl.enableVertexAttribArray(0); | |
gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0); | |
gl.getExtension('EXT_color_buffer_float'); | |
const texture = gl.createTexture(); | |
gl.bindTexture(gl.TEXTURE_2D, texture); | |
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST); | |
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST); | |
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE); | |
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE); | |
gl.texImage2D(gl.TEXTURE_2D, gl.NO_ERROR, gl.R32F, gl.LINE_LOOP, gl.LINE_LOOP, gl.NO_ERROR, gl.RED, gl.FLOAT, null); | |
const framebuffer = gl.createFramebuffer(); | |
gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer); | |
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, gl.NO_ERROR); | |
gl.bindTexture(gl.TEXTURE_2D, null); | |
const program = gl.createProgram(); | |
const vertexShader = gl.createShader(gl.VERTEX_SHADER); | |
gl.shaderSource(vertexShader, `#version 300 es | |
in vec4 vPosition; | |
void main() { | |
gl_Position = vPosition; | |
}`); | |
gl.compileShader(vertexShader); | |
gl.attachShader(program, vertexShader); | |
const fragmentShaderHandle = gl.createShader(gl.FRAGMENT_SHADER); | |
gl.shaderSource(fragmentShaderHandle, `#version 300 es | |
precision highp float; | |
out float num; | |
void main() | |
{ | |
num = 3.402823466e+38; | |
} | |
`); | |
gl.compileShader(fragmentShaderHandle); | |
console.log(gl.getShaderInfoLog(fragmentShaderHandle)); | |
console.log(gl.getShaderInfoLog(vertexShader)); | |
gl.attachShader(program, fragmentShaderHandle); | |
gl.linkProgram(program); | |
gl.useProgram(program); | |
console.log(gl.getProgramInfoLog(program)); | |
gl.drawArrays(gl.TRIANGLES, gl.NO_ERROR, gl.TRIANGLE_FAN); | |
gl.bindFramebuffer(gl.FRAMEBUFFER, null); | |
gl.bindTexture(gl.TEXTURE_2D, texture); | |
gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer); | |
const redFloatPixels = new Float32Array(16); | |
gl.readPixels(0, 0, 2, 2, gl.RED, gl.FLOAT, redFloatPixels); | |
// we want an Floats as output, no work, value is exactly what we need: | |
const result = redFloatPixels; | |
console.log(result); | |
</script> | |
</html> |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment