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<!DOCTYPE html>
<head>
<meta charset="utf-8"/>
<title>Мрежа от квадрати</title>
<script src="webgl-fmi.js"></script>
<script id="vshader" type="x-shader/x-vertex">
uniform mat4 uProjectionMatrix;
uniform mat4 uViewMatrix;
uniform mat4 uModelMatrix;
attribute vec3 aXYZ;
attribute vec3 aColor;
varying vec3 vColor;
void main ()
{
mat4 mvMatrix = uViewMatrix * uModelMatrix;
gl_Position = uProjectionMatrix * mvMatrix * vec4(aXYZ,1);
vColor = aColor;
}
</script>
<script id="fshader" type="x-shader/x-fragment">
precision mediump float;
varying vec3 vColor;
void main( )
{
gl_FragColor = vec4(vColor,1);
}
</script>
<script>
function start( )
{
var canvas = document.getElementById("picasso");
canvas.addEventListener('webglcontextlost',function(event){event.preventDefault();},false);
canvas.addEventListener('webglcontextrestored',function(){init();},false);
init();
drawFrame();
}
function init()
{
gl = getContext("picasso");
glprog = getProgram("vshader","fshader");
aXYZ = gl.getAttribLocation(glprog,"aXYZ");
uProjectionMatrix = gl.getUniformLocation(glprog,"uProjectionMatrix");
uViewMatrix = gl.getUniformLocation(glprog,"uViewMatrix");
uModelMatrix = gl.getUniformLocation(glprog,"uModelMatrix");
aColor = gl.getAttribLocation(glprog,"aColor");
gl.vertexAttrib3f(aColor,1,0.5,0);
gl.clearColor(1,1,1,1);
identity();
perspective(30,gl.canvas.width/gl.canvas.height,1,40000);
const N = 3;
const M = 8;
var data = [0,1,0];
for (var y = 0; y < M; y++) {
for (var n = y%2, x = y%2; n < N; x+=2, n++) {
data.push(x ,y,0, x+1,y+1,0, x+1,y ,0);
/* gl.TRIANGLE_STRIP работи, като поглежда последните две точки, за да направи
* триъгълник. Знаем, че ако някои две от 3те точки за един триъгълник съвпадат,
* няма да има триъгълник. Тоест, ако повторим последната точка и следващата
* (горе-ляво на следващия квадрат), то ще имаме дупката
*/
data.push(x+1,y,0, x+2,y+1,0, x+2,y+1,0);
}
if (y < M - 1) {
if (y % 2 === 0)
data.push(N*2 ,y+1,0, 1,y+2,0, 1,y+2,0);
else
data.push(N*2-1,y+1,0, 0,y+2,0, 0,y+2,0);
}
}
var buf = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER,buf);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(data), gl.STATIC_DRAW);
gl.enableVertexAttribArray(aXYZ);
gl.vertexAttribPointer(aXYZ,3,gl.FLOAT,false,3*FLOATS,0*FLOATS);
}
var frame = 0;
function drawFrame()
{
frame++;
gl.clear(gl.COLOR_BUFFER_BIT+gl.DEPTH_BUFFER_BIT);
lookAt([1/2,1/2,30], [1/2,1/2,0], [Math.sin(frame/200),Math.cos(frame/200),0]);
useMatrix();
// рисуване на мрежата от квадрати с едно
// извикване на drawArrays
gl.drawArrays(gl.TRIANGLE_STRIP,0,142);
requestAnimationFrame(drawFrame);
}
</script>
</head>
<body onload="start()">
<h2>Мрежа от квадрати</h2>
<noscript>
Искаме JavaScript, но няма!
</noscript>
<canvas id="picasso" width="600" height="400" style="border: solid;">
Искаме canvas, но няма!
</canvas>
</body>
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