webgl-fundamentals/webgl/webgl-2d-rectangle-with-random-colors.html at master · gfxfundamentals/webgl-fundamentals · GitHub

Name: webgl-fundamentals/webgl/webgl-2d-rectangle-with-random-colors.html at master · gfxfundamentals/webgl-fundamentals · GitHub
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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 - Rectangle with random colors</title>
<linktype="text/css" href="resources/webgl-tutorials.css" rel="stylesheet" />
</head>
<body>
<divclass="description">
Drag sliders to translate, rotate, and scale.
</div>
<canvasid="canvas"></canvas>
<divid="uiContainer">
<divid="ui">
<divid="x"></div>
<divid="y"></div>
<divid="angle"></div>
<divid="scaleX"></div>
<divid="scaleY"></div>
</div>
</div>
</body>
<!-- vertex shader -->
<scriptid="vertex-shader-2d" type="x-shader/x-vertex">
attributevec2a_position;
attributevec4a_color;

uniformmat3u_matrix;

varyingvec4v_color;

voidmain(){
// Multiply the position by the matrix.
gl_Position=vec4((u_matrix*vec3(a_position,1)).xy,0,1);

// Copy the color from the attribute to the varying.
v_color=a_color;
}
</script>
<!-- fragment shader -->
<scriptid="fragment-shader-2d" type="x-shader/x-fragment">
precisionmediumpfloat;

varyingvec4v_color;

voidmain(){
gl_FragColor=v_color;
}
</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/webgl-lessons-ui.js"></script>
<scriptsrc="resources/m3.js"></script>
<script>
"use strict";

functionmain(){
// Get A WebGL context
/** @type {HTMLCanvasElement} */
varcanvas=document.querySelector("#canvas");
vargl=canvas.getContext("webgl");
if(!gl){
return;
}

// setup GLSL program
varprogram=webglUtils.createProgramFromScripts(gl,["vertex-shader-2d","fragment-shader-2d"]);

// look up where the vertex data needs to go.
varpositionLocation=gl.getAttribLocation(program,"a_position");
varcolorLocation=gl.getAttribLocation(program,"a_color");

// lookup uniforms
varmatrixLocation=gl.getUniformLocation(program,"u_matrix");

// Create a buffer for the positions.
varpositionBuffer=gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER,positionBuffer);
// Set Geometry.
setGeometry(gl);

// Create a buffer for the colors.
varcolorBuffer=gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER,colorBuffer);
// Set the colors.
setColors(gl);

vartranslation=[200,150];
varangleInRadians=0;
varscale=[1,1];

drawScene();

// Setup a ui.
webglLessonsUI.setupSlider("#x",{value: translation[0],slide: updatePosition(0),max: gl.canvas.width});
webglLessonsUI.setupSlider("#y",{value: translation[1],slide: updatePosition(1),max: gl.canvas.height});
webglLessonsUI.setupSlider("#angle",{slide: updateAngle,max: 360});
webglLessonsUI.setupSlider("#scaleX",{value: scale[0],slide: updateScale(0),min: -5,max: 5,step: 0.01,precision: 2});
webglLessonsUI.setupSlider("#scaleY",{value: scale[1],slide: updateScale(1),min: -5,max: 5,step: 0.01,precision: 2});

functionupdatePosition(index){
returnfunction(event,ui){
translation[index]=ui.value;
drawScene();
};
}

functionupdateAngle(event,ui){
varangleInDegrees=360-ui.value;
angleInRadians=angleInDegrees*Math.PI/180;
drawScene();
}

functionupdateScale(index){
returnfunction(event,ui){
scale[index]=ui.value;
drawScene();
};
}

// Draw the scene.
functiondrawScene(){
webglUtils.resizeCanvasToDisplaySize(gl.canvas);

// Tell WebGL how to convert from clip space to pixels
gl.viewport(0,0,gl.canvas.width,gl.canvas.height);

// Clear the canvas.
gl.clear(gl.COLOR_BUFFER_BIT);

// Tell it to use our program (pair of shaders)
gl.useProgram(program);

// Turn on the position attribute
gl.enableVertexAttribArray(positionLocation);

// Bind the position buffer.
gl.bindBuffer(gl.ARRAY_BUFFER,positionBuffer);

// Tell the position attribute how to get data out of positionBuffer (ARRAY_BUFFER)
varsize=2;// 2 components per iteration
vartype=gl.FLOAT;// the data is 32bit floats
varnormalize=false;// don't normalize the data
varstride=0;// 0 = move forward size * sizeof(type) each iteration to get the next position
varoffset=0;// start at the beginning of the buffer
gl.vertexAttribPointer(
positionLocation,size,type,normalize,stride,offset);

// Turn on the color attribute
gl.enableVertexAttribArray(colorLocation);

// Bind the color buffer.
gl.bindBuffer(gl.ARRAY_BUFFER,colorBuffer);

// Tell the color attribute how to get data out of colorBuffer (ARRAY_BUFFER)
varsize=4;// 4 components per iteration
vartype=gl.FLOAT;// the data is 32bit floats
varnormalize=false;// don't normalize the data
varstride=0;// 0 = move forward size * sizeof(type) each iteration to get the next position
varoffset=0;// start at the beginning of the buffer
gl.vertexAttribPointer(
colorLocation,size,type,normalize,stride,offset);

// Compute the matrix
varmatrix=m3.projection(gl.canvas.clientWidth,gl.canvas.clientHeight);
matrix=m3.translate(matrix,translation[0],translation[1]);
matrix=m3.rotate(matrix,angleInRadians);
matrix=m3.scale(matrix,scale[0],scale[1]);

// Set the matrix.
gl.uniformMatrix3fv(matrixLocation,false,matrix);

// Draw the geometry.
varprimitiveType=gl.TRIANGLES;
varoffset=0;
varcount=6;
gl.drawArrays(primitiveType,offset,count);
}
}


// Fill the buffer with the values that define a rectangle.
// Note, will put the values in whatever buffer is currently
// bound to the ARRAY_BUFFER bind point
functionsetGeometry(gl){
gl.bufferData(
gl.ARRAY_BUFFER,
newFloat32Array([
-150,-100,
150,-100,
-150,100,
150,-100,
-150,100,
150,100]),
gl.STATIC_DRAW);
}

// Fill the buffer with colors for the 2 triangles
// that make the rectangle.
// Note, will put the values in whatever buffer is currently
// bound to the ARRAY_BUFFER bind point
functionsetColors(gl){
// Make every vertex a different color.
gl.bufferData(
gl.ARRAY_BUFFER,
newFloat32Array(
[Math.random(),Math.random(),Math.random(),1,
Math.random(),Math.random(),Math.random(),1,
Math.random(),Math.random(),Math.random(),1,
Math.random(),Math.random(),Math.random(),1,
Math.random(),Math.random(),Math.random(),1,
Math.random(),Math.random(),Math.random(),1]),
gl.STATIC_DRAW);
}

main();
</script>
</html>