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一、实例代码
<html>
<canvas id='c' width='640' height='480'></canvas>
<script type="x-shader/x-vertex" id="vertex-shader">
attribute vec4 a_position;
attribute vec2 aTextureCoord;
uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;
varying highp vec2 vTextureCoord;
void main(){
gl_Position = projection * view * model * a_position;
vTextureCoord = aTextureCoord;
}
</script>
<script type="x-shader/x-fragment" id="fragment-shader">
varying highp vec2 vTextureCoord;
uniform sampler2D uSampler;
void main(){
gl_FragColor = texture2D(uSampler, vTextureCoord);
}
</script>
<script src="WebGLUtils.js"> </script>
<script src="gl-matrix.js"></script>
<script>
var rotation = 0.0
var gl = createGLContext('c')
// alert(gl.getParameter(gl.MAX_TEXTURE_IMAGE_UNITS))
//创建shader program
var program = createProgramFromElementId(gl,'vertex-shader','fragment-shader');
gl.useProgram(program);
function initBuffers(gl,program){
// 坐标数据写入GPU缓冲区
const positions = [
// Front face
-1.0, -1.0, 1.0,
1.0, -1.0, 1.0,
1.0, 1.0, 1.0,
-1.0, 1.0, 1.0,
// Back face
-1.0, -1.0, -1.0,
-1.0, 1.0, -1.0,
1.0, 1.0, -1.0,
1.0, -1.0, -1.0,
// Top face
-1.0, 1.0, -1.0,
-1.0, 1.0, 1.0,
1.0, 1.0, 1.0,
1.0, 1.0, -1.0,
// Bottom face
-1.0, -1.0, -1.0,
1.0, -1.0, -1.0,
1.0, -1.0, 1.0,
-1.0, -1.0, 1.0,
// Right face
1.0, -1.0, -1.0,
1.0, 1.0, -1.0,
1.0, 1.0, 1.0,
1.0, -1.0, 1.0,
// Left face
-1.0, -1.0, -1.0,
-1.0, -1.0, 1.0,
-1.0, 1.0, 1.0,
-1.0, 1.0, -1.0,
];
var FSIZE = positions.BYTES_PER_ELEMENT;
const positionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STATIC_DRAW);
// 向着色器传递坐标数据
var a_position = gl.getAttribLocation(program,"a_position");
gl.enableVertexAttribArray(a_position);
gl.vertexAttribPointer(a_position,3,gl.FLOAT,false,3*FSIZE,0);
// 纹理坐标数据写入GPU缓冲区
const textureCoordinates = [
// Front
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
// Back
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
// Top
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
// Bottom
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
// Right
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
// Left
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
];
const textureCoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, textureCoordBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoordinates),gl.STATIC_DRAW);
// 向着色器传递纹理坐标数据
var textureCoord = gl.getAttribLocation(program,"aTextureCoord");
gl.enableVertexAttribArray(textureCoord);
gl.vertexAttribPointer(textureCoord,2,gl.FLOAT,false,2*FSIZE,0);
// 创建索引缓冲对象
const indices = [
0, 1, 2, 0, 2, 3, // front
4, 5, 6, 4, 6, 7, // back
8, 9, 10, 8, 10, 11, // top
12, 13, 14, 12, 14, 15, // bottom
16, 17, 18, 16, 18, 19, // right
20, 21, 22, 20, 22, 23, // left
];
const indexBuffer = gl.createBuffer();
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER,
new Uint16Array(indices), gl.STATIC_DRAW);
}
function loadTexture(gl,program){
const image = new Image();
image.src = "./cubetexture.png"
image.onload = function(){
//-----将图像数据复制到GPU缓冲区-----//
const texture = gl.createTexture();
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D,texture);
gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, 1)
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);
gl.generateMipmap(gl.TEXTURE_2D);
//-----向着色器传递纹理数据-----//
var u_Sampler = gl.getUniformLocation(program, 'uSampler');
gl.uniform1i(u_Sampler, 0);
}
}
initBuffers(gl,program);
loadTexture(gl,program)
function drawScene(gl,deltaTime){
gl.clearColor(0.0, 0.0, 0.0, 1.0)
gl.clearDepth(1.0)
gl.enable(gl.DEPTH_TEST)
gl.depthFunc(gl.LEQUAL);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
//-------创建投影矩阵-----------//
var projection = mat4.create()
// 视野，观察空间的大小
const fieldOfView = 45 * Math.PI / 180;
const aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
const zNear = 0.1;
const zFar = 100.0;
mat4.perspective(projection,
fieldOfView,
aspect,
zNear,
zFar);
// mat4.ortho(projection,0.0, 800, 0.0, 600, 0.1, 100.0)
var projection_matrix = gl.getUniformLocation(program, 'projection')
gl.uniformMatrix4fv(projection_matrix,false,projection)
//---------------------------//
//-------创建模型矩阵-----------//
var model = mat4.create()
mat4.rotate(model,model,rotation,[1,0,0])
mat4.rotate(model,model,rotation*.7,[0,1,0])
var model_matrix = gl.getUniformLocation(program, 'model')
gl.uniformMatrix4fv(model_matrix,false,model)
//----------------------------//
//-------创建观察矩阵-----------//
var view = mat4.create()
mat4.translate(view,view,[-0.0, 0.0, -6.0])
var view_matrix = gl.getUniformLocation(program, 'view')
gl.uniformMatrix4fv(view_matrix,false,view)
//----------------------------//
{
const vertexCount = 36;
const type = gl.UNSIGNED_SHORT;
const offset = 0;
gl.drawElements(gl.TRIANGLES, vertexCount, type, offset);
}
rotation += deltaTime;
}
var old = 0
function render(now) {
now *= 0.001; // convert to seconds
const deltaTime = now - old;
old = now;
drawScene(gl,deltaTime);
requestAnimationFrame(render);
}
requestAnimationFrame(render);
</script>
</html>
