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webgl-canvas-width-height.html
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<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
<title>WebGL2 - projection using width, height (BAD!)</title>
<link type="text/css" href="resources/webgl-tutorials.css" rel="stylesheet" />
<style>
body {
margin: 0px;
}
canvas {
display: block;
width: 100vw;
height: 100vh;
border: 0px !important;
}
h1 {
position: absolute;
left: 10px;
}
.description {
position: absolute;
left: 10px;
bottom: 10px;
text-shadow:
-1px -1px 0 #FFF,
1px -1px 0 #FFF,
-1px 1px 0 #FFF,
1px 1px 0 #FFF;
}
.iframe .description {
display: none;
}
</style>
</head>
<body>
<canvas id="canvas" width="400" height="300"></canvas>
<div class="description">resize this window tall and thin or short and wide.<br/>Notice the F does NOT keep the correct aspect</div>
</body>
<script src="resources/webgl-utils.js"></script>
<script src="resources/webgl-lessons-helper.js"></script>
<script src="resources/2d-math.js"></script>
<script>
"use strict";
var vertexShaderSource = `#version 300 es
// an attribute is an input (in) to a vertex shader.
// It will receive data from a buffer
in vec2 a_position;
// A matrix to transform the positions by
uniform mat3 u_matrix;
// all shaders have a main function
void main() {
// Multiply the position by the matrix.
gl_Position = vec4((u_matrix * vec3(a_position, 1)).xy, 0, 1);
}
`;
var fragmentShaderSource = `#version 300 es
precision mediump float;
uniform vec4 u_color;
// we need to declare an output for the fragment shader
out vec4 outColor;
void main() {
outColor = u_color;
}
`;
function main() {
// Get A WebGL context
var canvas = document.getElementById("canvas");
webglLessonsHelper.setupLesson(canvas, {}, {dontResize:true});
/** @type {WebGLRenderingContext} */
var gl = canvas.getContext("webgl2");
if (!gl) {
webglLessonsHelper.showNeedWebGL2(canvas);
return;
}
// Use our boilerplate utils to compile the shaders and link into a program
var program = webglUtils.createProgramFromSources(gl,
[vertexShaderSource, fragmentShaderSource]);
// look up where the vertex data needs to go.
var positionAttributeLocation = gl.getAttribLocation(program, "a_position");
// look up uniform locations
var colorLocation = gl.getUniformLocation(program, "u_color");
var matrixLocation = gl.getUniformLocation(program, "u_matrix");
// Create a buffer
var positionBuffer = gl.createBuffer();
// Create a vertex array object (attribute state)
var vao = gl.createVertexArray();
// and make it the one we're currently working with
gl.bindVertexArray(vao);
// Turn on the attribute
gl.enableVertexAttribArray(positionAttributeLocation);
// Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = positionBuffer)
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Set Geometry.
setGeometry(gl);
// Tell the attribute how to get data out of positionBuffer (ARRAY_BUFFER)
var size = 2; // 2 components per iteration
var type = gl.FLOAT; // the data is 32bit floats
var normalize = false; // don't normalize the data
var stride = 0; // 0 = move forward size * sizeof(type) each iteration to get the next position
var offset = 0; // start at the beginning of the buffer
gl.vertexAttribPointer(
positionAttributeLocation, size, type, normalize, stride, offset);
var translation = [30, 10];
var rotationInRadians = 0;
var scale = [1, 1];
var color = [Math.random(), Math.random(), Math.random(), 1];
drawScene();
// Draw the scene.
function drawScene() {
// Tell WebGL how to convert from clip space to pixels
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
// Clear the canvas
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
// Tell it to use our program (pair of shaders)
gl.useProgram(program);
// Bind the attribute/buffer set we want.
gl.bindVertexArray(vao);
// Set the color.
gl.uniform4fv(colorLocation, color);
// Compute the matrices
var matrix = m3.projection(gl.canvas.width, gl.canvas.height); // BAD!
matrix = m3.translate(matrix, translation[0], translation[1]);
matrix = m3.rotate(matrix, rotationInRadians);
matrix = m3.scale(matrix, scale[0], scale[1]);
// Set the matrix.
gl.uniformMatrix3fv(matrixLocation, false, matrix);
// Draw the geometry.
var primitiveType = gl.TRIANGLES;
var offset = 0;
var count = 18;
gl.drawArrays(primitiveType, offset, count);
}
window.addEventListener('resize', drawScene, false);
}
// Fill the current ARRAY_BUFFER buffer
// with the values that define a letter 'F'.
function setGeometry(gl) {
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array([
// left column
0, 0,
30, 0,
0, 150,
0, 150,
30, 0,
30, 150,
// top rung
30, 0,
100, 0,
30, 30,
30, 30,
100, 0,
100, 30,
// middle rung
30, 60,
67, 60,
30, 90,
30, 90,
67, 60,
67, 90]),
gl.STATIC_DRAW);
}
main();
</script>
</html>