webgl-fundamentals/webgl/webgl-2d-triangle-with-position-for-color.html at master · gfxfundamentals/webgl-fundamentals · GitHub

Name: webgl-fundamentals/webgl/webgl-2d-triangle-with-position-for-color.html at master · gfxfundamentals/webgl-fundamentals · GitHub
Rating: 4.6 (944 reviews)
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
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
<!-- 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 - Triangle with position for color</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;

uniformmat3u_matrix;

varyingvec4v_color;

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

// Convert from clipspace to colorspace.
// Clipspace goes -1.0 to +1.0
// Colorspace goes from 0.0 to 1.0
v_color=gl_Position*0.5+0.5;
}
</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.
varpositionAttributeLocation=gl.getAttribLocation(program,"a_position");

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

// Create a buffer.
varpositionBuffer=gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER,positionBuffer);

// Set Geometry.
setGeometry(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 attribute
gl.enableVertexAttribArray(positionAttributeLocation);

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

// Tell the 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(
positionAttributeLocation,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=3;
gl.drawArrays(primitiveType,offset,count);
}
}

// Fill the buffer with the values that define a triangle.
// 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([
0,-100,
150,125,
-175,100]),
gl.STATIC_DRAW);
}

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