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webgl-2d-geometry-matrix-transform-trs.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 - 2D Geometry Matrix Transform Reverse Order</title>
<link type="text/css" href="resources/webgl-tutorials.css" rel="stylesheet" />
</head>
<body>
<div class="description">
Drag sliders to translate, rotate, and scale.
</div>
<canvas id="canvas" width="400" height="300"></canvas>
<div id="uiContainer">
<div id="ui">
<div id="x"></div>
<div id="y"></div>
<div id="angle"></div>
<div id="scaleX"></div>
<div id="scaleY"></div>
</div>
</div>
</body>
<script src="resources/webgl-utils.js"></script>
<script src="resources/webgl-lessons-helper.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;
// Used to pass in the resolution of the canvas
uniform vec2 u_resolution;
// 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.
vec2 position = (u_matrix * vec3(a_position, 1)).xy;
// convert the position from pixels to 0.0 to 1.0
vec2 zeroToOne = position / u_resolution;
// convert from 0->1 to 0->2
vec2 zeroToTwo = zeroToOne * 2.0;
// convert from 0->2 to -1->+1 (clipspace)
vec2 clipSpace = zeroToTwo - 1.0;
gl_Position = vec4(clipSpace * vec2(1, -1), 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);
/** @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 resolutionUniformLocation = gl.getUniformLocation(program, "u_resolution");
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);
// First let's make some variables
// to hold the translation,
var translation = [150, 100];
var rotationInRadians = 0;
var scale = [1, 1];
var color = [Math.random(), Math.random(), Math.random(), 1];
drawScene();
// Setup a ui.
webglLessonsHelper.setupSlider("#x", {value: translation[0], slide: updatePosition(0), max: gl.canvas.width });
webglLessonsHelper.setupSlider("#y", {value: translation[1], slide: updatePosition(1), max: gl.canvas.height});
webglLessonsHelper.setupSlider("#angle", {value: rotationInRadians * 180 / Math.PI | 0, slide: updateAngle, max: 360});
webglLessonsHelper.setupSlider("#scaleX", {value: scale[0], slide: updateScale(0), min: -5, max: 5, step: 0.01, precision: 2});
webglLessonsHelper.setupSlider("#scaleY", {value: scale[1], slide: updateScale(1), min: -5, max: 5, step: 0.01, precision: 2});
function updatePosition(index) {
return function(event, ui) {
translation[index] = ui.value;
drawScene();
}
}
function updateAngle(event, ui) {
var angleInDegrees = 360 - ui.value;
rotationInRadians = angleInDegrees * Math.PI / 180;
drawScene();
}
function updateScale(index) {
return function(event, ui) {
scale[index] = ui.value;
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);
// Pass in the canvas resolution so we can convert from
// pixels to clipspace in the shader
gl.uniform2f(resolutionUniformLocation, gl.canvas.width, gl.canvas.height);
// Set the color.
gl.uniform4fv(colorLocation, color);
// Compute the matrices
var translationMatrix = m3.translation(translation[0], translation[1]);
var rotationMatrix = m3.rotation(rotationInRadians);
var scaleMatrix = m3.scaling(scale[0], scale[1]);
// Multiply the matrices.
var matrix = m3.multiply(scaleMatrix, rotationMatrix);
matrix = m3.multiply(matrix, translationMatrix);
// 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);
}
}
// 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);
}
var m3 = {
translation: function translation(tx, ty) {
return [
1, 0, 0,
0, 1, 0,
tx, ty, 1
];
},
rotation: function rotation(angleInRadians) {
var c = Math.cos(angleInRadians);
var s = Math.sin(angleInRadians);
return [
c,-s, 0,
s, c, 0,
0, 0, 1
];
},
scaling: function scaling(sx, sy) {
return [
sx, 0, 0,
0, sy, 0,
0, 0, 1
];
},
multiply: function multiply(a, b) {
var a00 = a[0*3+0];
var a01 = a[0*3+1];
var a02 = a[0*3+2];
var a10 = a[1*3+0];
var a11 = a[1*3+1];
var a12 = a[1*3+2];
var a20 = a[2*3+0];
var a21 = a[2*3+1];
var a22 = a[2*3+2];
var b00 = b[0*3+0];
var b01 = b[0*3+1];
var b02 = b[0*3+2];
var b10 = b[1*3+0];
var b11 = b[1*3+1];
var b12 = b[1*3+2];
var b20 = b[2*3+0];
var b21 = b[2*3+1];
var b22 = b[2*3+2];
return [b00 * a00 + b01 * a10 + b02 * a20,
b00 * a01 + b01 * a11 + b02 * a21,
b00 * a02 + b01 * a12 + b02 * a22,
b10 * a00 + b11 * a10 + b12 * a20,
b10 * a01 + b11 * a11 + b12 * a21,
b10 * a02 + b11 * a12 + b12 * a22,
b20 * a00 + b21 * a10 + b22 * a20,
b20 * a01 + b21 * a11 + b22 * a21,
b20 * a02 + b21 * a12 + b22 * a22];
},
};
main();
</script>
</html>