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webgl-2d-matrixstack-03.html
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<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
<head>
<metacharset="utf-8">
<metaname="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
<title>WebGL - 2D - DrawImage with MatrixStack images at 4 corners</title>
<linktype="text/css" href="resources/webgl-tutorials.css" rel="stylesheet" />
</head>
<body>
<canvasid="canvas"></canvas>
</body>
<!-- vertex shader -->
<scriptid="drawImage-vertex-shader" type="x-shader/x-vertex">
attributevec4a_position;
attributevec2a_texcoord;
uniformmat4u_matrix;
uniformmat4u_textureMatrix;
varyingvec2v_texcoord;
voidmain(){
gl_Position=u_matrix*a_position;
v_texcoord=(u_textureMatrix*vec4(a_texcoord,0,1)).xy;
}
</script>
<scriptid="drawImage-fragment-shader" type="x-shader/x-fragment">
precisionmediumpfloat;
varyingvec2v_texcoord;
uniformsampler2Dtexture;
voidmain(){
gl_FragColor=texture2D(texture,v_texcoord);
}
</script>
<!--
for most samples webgl-utils only provides shader compiling/linking and
canvas resizing because why clutter the examples with code that's the same in every sample.
See https://webglfundamentals.org/webgl/lessons/webgl-boilerplate.html
and https://webglfundamentals.org/webgl/lessons/webgl-resizing-the-canvas.html
for webgl-utils, m3, m4, and webgl-lessons-ui.
-->
<scriptsrc="resources/webgl-utils.js"></script>
<scriptsrc="resources/m4.js"></script>
<script>
"use strict";
functionmain(){
// Get A WebGL context
/** @type {HTMLCanvasElement} */
varcanvas=document.querySelector("#canvas");
vargl=canvas.getContext("webgl");
if(!gl){
return;
}
varmatrixStack=newMatrixStack();
// setup GLSL program
varprogram=webglUtils.createProgramFromScripts(gl,["drawImage-vertex-shader","drawImage-fragment-shader"]);
// look up where the vertex data needs to go.
varpositionLocation=gl.getAttribLocation(program,"a_position");
vartexcoordLocation=gl.getAttribLocation(program,"a_texcoord");
// lookup uniforms
varmatrixLocation=gl.getUniformLocation(program,"u_matrix");
vartextureMatrixLocation=gl.getUniformLocation(program,"u_textureMatrix");
vartextureLocation=gl.getUniformLocation(program,"u_texture");
// Create a buffer.
varpositionBuffer=gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER,positionBuffer);
// Put a unit quad in the buffer
varpositions=[
0,0,
0,1,
1,0,
1,0,
0,1,
1,1,
];
gl.bufferData(gl.ARRAY_BUFFER,newFloat32Array(positions),gl.STATIC_DRAW);
// Create a buffer for texture coords
vartexcoordBuffer=gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER,texcoordBuffer);
// Put texcoords in the buffer
vartexcoords=[
0,0,
0,1,
1,0,
1,0,
0,1,
1,1,
];
gl.bufferData(gl.ARRAY_BUFFER,newFloat32Array(texcoords),gl.STATIC_DRAW);
// creates a texture info { width: w, height: h, texture: tex }
// The texture will start with 1x1 pixels and be updated
// when the image has loaded
functionloadImageAndCreateTextureInfo(url){
vartex=gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D,tex);
// Fill the texture with a 1x1 blue pixel.
gl.texImage2D(gl.TEXTURE_2D,0,gl.RGBA,1,1,0,gl.RGBA,gl.UNSIGNED_BYTE,
newUint8Array([0,0,255,255]));
// let's assume all images are not a power of 2
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.texParameteri(gl.TEXTURE_2D,gl.TEXTURE_MIN_FILTER,gl.LINEAR);
vartextureInfo={
width: 1,// we don't know the size until it loads
height: 1,
texture: tex,
};
varimg=newImage();
img.addEventListener('load',function(){
textureInfo.width=img.width;
textureInfo.height=img.height;
gl.bindTexture(gl.TEXTURE_2D,textureInfo.texture);
gl.texImage2D(gl.TEXTURE_2D,0,gl.RGBA,gl.RGBA,gl.UNSIGNED_BYTE,img);
});
img.src=url;
returntextureInfo;
}
vartextureInfo=loadImageAndCreateTextureInfo('resources/star.jpg');
functiondraw(time){
webglUtils.resizeCanvasToDisplaySize(gl.canvas);
// Tell WebGL how to convert from clip space to pixels
gl.viewport(0,0,gl.canvas.width,gl.canvas.height);
gl.clear(gl.COLOR_BUFFER_BIT);
matrixStack.save();
matrixStack.translate(gl.canvas.width/2,gl.canvas.height/2);
matrixStack.rotateZ(time);
matrixStack.save();
{
matrixStack.translate(textureInfo.width/-2,textureInfo.height/-2);
drawImage(
textureInfo.texture,
textureInfo.width,
textureInfo.height,
0,0);
}
matrixStack.restore();
matrixStack.save();
{
// We're at the center of the center image so go to the top/left corner
matrixStack.translate(textureInfo.width/-2,textureInfo.height/-2);
matrixStack.rotateZ(Math.sin(time*2.2));
matrixStack.scale(0.2,0.2);
// Now we want the bottom/right corner of the image we're about to draw
matrixStack.translate(-textureInfo.width,-textureInfo.height);
drawImage(
textureInfo.texture,
textureInfo.width,
textureInfo.height,
0,0);
}
matrixStack.restore();
matrixStack.save();
{
// We're at the center of the center image so go to the top/right corner
matrixStack.translate(textureInfo.width/2,textureInfo.height/-2);
matrixStack.rotateZ(Math.sin(time*2.3));
matrixStack.scale(0.2,0.2);
// Now we want the bottom/right corner of the image we're about to draw
matrixStack.translate(0,-textureInfo.height);
drawImage(
textureInfo.texture,
textureInfo.width,
textureInfo.height,
0,0);
}
matrixStack.restore();
matrixStack.save();
{
// We're at the center of the center image so go to the bottom/left corner
matrixStack.translate(textureInfo.width/-2,textureInfo.height/2);
matrixStack.rotateZ(Math.sin(time*2.4));
matrixStack.scale(0.2,0.2);
// Now we want the top/right corner of the image we're about to draw
matrixStack.translate(-textureInfo.width,0);
drawImage(
textureInfo.texture,
textureInfo.width,
textureInfo.height,
0,0);
}
matrixStack.restore();
matrixStack.save();
{
// We're at the center of the center image so go to the bottom/right corner
matrixStack.translate(textureInfo.width/2,textureInfo.height/2);
matrixStack.rotateZ(Math.sin(time*2.5));
matrixStack.scale(0.2,0.2);
// Now we want the top/left corner of the image we're about to draw
matrixStack.translate(0,0);// 0,0 means this line is not really doing anything
drawImage(
textureInfo.texture,
textureInfo.width,
textureInfo.height,
0,0);
}
matrixStack.restore();
matrixStack.restore();
}
varthen=0;
functionrender(time){
time*=0.001;
varnow=time;
vardeltaTime=Math.min(0.1,now-then);
then=now;
draw(time);
requestAnimationFrame(render);
}
requestAnimationFrame(render);
// Unlike images, textures do not have a width and height associated
// with them so we'll pass in the width and height of the texture
functiondrawImage(
tex,texWidth,texHeight,
srcX,srcY,srcWidth,srcHeight,
dstX,dstY,dstWidth,dstHeight){
if(dstX===undefined){
dstX=srcX;
}
if(dstY===undefined){
dstY=srcY;
}
if(srcWidth===undefined){
srcWidth=texWidth;
}
if(srcHeight===undefined){
srcHeight=texHeight;
}
if(dstWidth===undefined){
dstWidth=srcWidth;
}
if(dstHeight===undefined){
dstHeight=srcHeight;
}
gl.bindTexture(gl.TEXTURE_2D,tex);
// Tell WebGL to use our shader program pair
gl.useProgram(program);
// Setup the attributes to pull data from our buffers
gl.bindBuffer(gl.ARRAY_BUFFER,positionBuffer);
gl.enableVertexAttribArray(positionLocation);
gl.vertexAttribPointer(positionLocation,2,gl.FLOAT,false,0,0);
gl.bindBuffer(gl.ARRAY_BUFFER,texcoordBuffer);
gl.enableVertexAttribArray(texcoordLocation);
gl.vertexAttribPointer(texcoordLocation,2,gl.FLOAT,false,0,0);
// this matrix will convert from pixels to clip space
varmatrix=m4.orthographic(0,gl.canvas.width,gl.canvas.height,0,-1,1);
// this matrix moves the origin to the one represented by
// the current matrix stack.
matrix=m4.multiply(matrix,matrixStack.getCurrentMatrix());
// this matrix will translate our quad to dstX, dstY
matrix=m4.translate(matrix,dstX,dstY,0);
// this matrix will scale our 1 unit quad
// from 1 unit to texWidth, texHeight units
matrix=m4.scale(matrix,dstWidth,dstHeight,1);
// Set the matrix.
gl.uniformMatrix4fv(matrixLocation,false,matrix);
// Because texture coordinates go from 0 to 1
// and because our texture coordinates are already a unit quad
// we can select an area of the texture by scaling the unit quad
// down
vartexMatrix=m4.translation(srcX/texWidth,srcY/texHeight,0);
texMatrix=m4.scale(texMatrix,srcWidth/texWidth,srcHeight/texHeight,1);
// Set the texture matrix.
gl.uniformMatrix4fv(textureMatrixLocation,false,texMatrix);
// Tell the shader to get the texture from texture unit 0
gl.uniform1i(textureLocation,0);
// draw the quad (2 triangles, 6 vertices)
gl.drawArrays(gl.TRIANGLES,0,6);
}
}
functionMatrixStack(){
this.stack=[];
// since the stack is empty this will put an initial matrix in it
this.restore();
}
// Pops the top of the stack restoring the previously saved matrix
MatrixStack.prototype.restore=function(){
this.stack.pop();
// Never let the stack be totally empty
if(this.stack.length<1){
this.stack[0]=m4.identity();
}
};
// Pushes a copy of the current matrix on the stack
MatrixStack.prototype.save=function(){
this.stack.push(this.getCurrentMatrix());
};
// Gets a copy of the current matrix (top of the stack)
MatrixStack.prototype.getCurrentMatrix=function(){
returnthis.stack[this.stack.length-1].slice();
};
// Lets us set the current matrix
MatrixStack.prototype.setCurrentMatrix=function(m){
this.stack[this.stack.length-1]=m;
returnm;
};
// Translates the current matrix
MatrixStack.prototype.translate=function(x,y,z){
if(z===undefined){
z=0;
}
varm=this.getCurrentMatrix();
this.setCurrentMatrix(m4.translate(m,x,y,z));
};
// Rotates the current matrix around Z
MatrixStack.prototype.rotateZ=function(angleInRadians){
varm=this.getCurrentMatrix();
this.setCurrentMatrix(m4.zRotate(m,angleInRadians));
};
// Scales the current matrix
MatrixStack.prototype.scale=function(x,y,z){
if(z===undefined){
z=1;
}
varm=this.getCurrentMatrix();
this.setCurrentMatrix(m4.scale(m,x,y,z));
};
main();
</script>
</html>
