1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
|
<!DOCTYPE html>
<head>
<meta charset="utf-8"/>
<title>Триъгълник на Рольо</title>
<script src="webgl-fmi.js"></script>
<script id="vshader" type="x-shader/x-vertex">
attribute vec2 aXY;
attribute vec3 aRGB;
varying vec3 vRGB;
void main ()
{
gl_Position = vec4(aXY,0,1);
gl_PointSize = 4.0;
vRGB = aRGB;
}
</script>
<script id="fshader" type="x-shader/x-fragment">
precision mediump float;
varying vec3 vRGB;
void main( )
{
gl_FragColor = vec4(vRGB,1);
}
</script>
<script>
function start( )
{
gl = getContext("picasso");
glprog = getProgram("vshader","fshader");
aXY = gl.getAttribLocation(glprog,"aXY");
aRGB = gl.getAttribLocation(glprog,"aRGB");
gl.clearColor(1,1,1,1);
gl.clear(gl.COLOR_BUFFER_BIT);
// параметър n за точност на дъгите в триъгълника
var n = 50;
var data = [];
const aspectRatio = 600 / 400;
const size = 0.8;
const r = 2 * size;
const step = 60 / n;
// Bottom-left point, right side
var originX = -size / aspectRatio;
var originY = -size + 0.2;
data.push(originX, originY);
for (var i = 30; i < 91; i += step)
data.push(Math.sin(2.0 * Math.PI * i / 360) * r / aspectRatio + originX, Math.cos(2.0 * Math.PI * i / 360) * r + originY);
// Bottom-right point, left side
var originX = size / aspectRatio;
data.push(originX, originY);
for (var i = 270; i < 331; i += step)
data.push(Math.sin(2 * Math.PI * i / 360) * r / aspectRatio + originX, Math.cos(2 * Math.PI * i / 360) * r + originY);
// Top point, bottom side
var originX = 0;
var originY = Math.sqrt(r * r - size * size) - size + 0.2;
data.push(originX, originY);
for (var i = 210; i > 149; i -= step)
data.push(Math.sin(2 * Math.PI * i / 360) * r / aspectRatio + originX, Math.cos(2 * Math.PI * i / 360) * r + originY);
// WebGL stuff
var buf = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER,buf);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(data), gl.STATIC_DRAW);
gl.vertexAttrib3f(aRGB,1,0.5,0);
gl.enableVertexAttribArray(aXY);
gl.vertexAttribPointer(aXY,2,gl.FLOAT,false,0,0);
gl.drawArrays(gl.TRIANGLE_FAN, 0, 2 + n);
gl.drawArrays(gl.TRIANGLE_FAN, 2 + n, 2 + n);
gl.drawArrays(gl.TRIANGLE_FAN, 2 * (2 + n), 2 + n);
}
</script>
</head>
<body onload="start()">
<h2>Триъгълник на Рольо</h2>
<noscript>
Искаме JavaScript, но няма!
</noscript>
<canvas id="picasso" width="600" height="400" style="border: solid;">
Искаме canvas, но няма!
</canvas>
</body>
|
