webgl学习笔记三-平移旋转缩放
写在前面
建议先阅读下前面我的两篇文章。
webgl学习笔记一-绘图单点
webgl学习笔记二-绘图多点
平移
1、关键点说明
顶点着色器需要加上 uniform vec4 u_Translation, 存储平移的坐标矢量。
顶点坐标位置 ： gl_Position = a_Position + u_Translation
平移API ： gl.uniform4f(u_Translation, Tx, Ty, Tz, 0.0);
2、demo
- html
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Titletitle>
head>
<body>
<canvas id="canvas" width="200px" height="200px">canvas>
body>
html>- JavaScript
<script>
function main() {
//顶点着色器程序
var VSHADER_SOURCE =
'attribute vec4 a_Position;\n' +
'uniform vec4 u_Translation;\n' +
'void main() {\n' +
' gl_Position = a_Position + u_Translation;\n' +
'}\n';
//片元着色器
var FSHADER_SOURCE =
'void main() {\n' +
' gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n' +
'}\n';
//获取canvas元素
var canvas = document.getElementById('canvas');
//获取绘制二维上下文
var gl = canvas.getContext('webgl');
if (!gl) {
console.log("Failed");
return;
}
//编译着色器
var vertShader = gl.createShader(gl.VERTEX_SHADER);
gl.shaderSource(vertShader, VSHADER_SOURCE);
gl.compileShader(vertShader);
var fragShader = gl.createShader(gl.FRAGMENT_SHADER);
gl.shaderSource(fragShader, FSHADER_SOURCE);
gl.compileShader(fragShader);
//合并程序
var shaderProgram = gl.createProgram();
gl.attachShader(shaderProgram, vertShader);
gl.attachShader(shaderProgram, fragShader);
gl.linkProgram(shaderProgram);
gl.useProgram(shaderProgram);
//获取坐标点
var a_Position = gl.getAttribLocation(shaderProgram, 'a_Position');
if (a_Position < 0) {
console.log('Failed to get the storage location of a_Position');
return;
}
var n = initBuffers(gl, shaderProgram);
if (n < 0) {
console.log('Failed to set the positions');
return;
}
// 清除指定<画布>的颜色
gl.clearColor(0.0, 0.0, 0.0, 1.0);
// 清空
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.TRIANGLES, 0, n);
}
function opt(gl, shaderProgram) {
var Tx = 0.5, Ty = 0.5, Tz = 0.0;
var u_Translation = gl.getUniformLocation(shaderProgram, 'u_Translation');
if (!u_Translation) {
console.log('Failed to get the storage location of u_Translation');
return;
}
gl.uniform4f(u_Translation, Tx, Ty, Tz, 0.0);
}
function initBuffers(gl, shaderProgram) {
var vertices = new Float32Array([
0, 0.5, -0.5, -0.5, 0.5, -0.5
]);
var n = 3;//点的个数
//创建缓冲区对象
var vertexBuffer = gl.createBuffer();
if (!vertexBuffer) {
console.log("Failed to create the butter object");
return -1;
}
//将缓冲区对象绑定到目标
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
//向缓冲区写入数据
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
//获取坐标点
var a_Position = gl.getAttribLocation(shaderProgram, 'a_Position');
//将缓冲区对象分配给a_Position变量
gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);
//连接a_Position变量与分配给它的缓冲区对象
gl.enableVertexAttribArray(a_Position);
return n;
}
main();
script>
旋转
1、关键点说明
- 坐标P（x,y,z） , 绕Z轴旋转β角度变成 p1（x1, y1, z1）
则根据数据三角函数公式可得：
x1 = xcosβ - ysinβ
y1 = xsinβ + ycosβ
z1=z
顶点着色器需要加上 uniform float u_CosB, u_SinB 存储旋转角度。
顶点坐标位置 ：
- gl_Position.x = a_Position.x * u_CosB - a_Position.y * u_SinB
- gl_Position.y = a_Position.x * u_SinB + a_Position.y * u_CosB
旋转API ：
- gl.uniform1f(u_CosB, cosB)
- gl.uniform1f(u_sinB, sinB);
2、demo
- JavaScript
<script>
function main() {
//顶点着色器程序
var VSHADER_SOURCE =
'attribute vec4 a_Position;\n' +
'uniform float u_CosB, u_SinB;\n' +
'void main() {\n' +
' gl_Position.x = a_Position.x * u_CosB - a_Position.y * u_SinB;\n' +
' gl_Position.y = a_Position.x * u_SinB + a_Position.y * u_CosB;\n' +
' gl_Position.z = a_Position.z;\n' +
' gl_Position.w = 1.0;\n' +
'}\n';
//片元着色器程序
var FSHADER_SOURCE =
'void main() {\n' +
' gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n' +
'}\n';
var Tx = 0.5, Ty = 0.5, Tz = 0.0;
//获取canvas元素
var canvas = document.getElementById('canvas');
//获取绘制二维上下文
var gl = canvas.getContext('webgl');
if (!gl) {
console.log("Failed");
return;
}
//编译着色器
var vertShader = gl.createShader(gl.VERTEX_SHADER);
gl.shaderSource(vertShader, VSHADER_SOURCE);
gl.compileShader(vertShader);
var fragShader = gl.createShader(gl.FRAGMENT_SHADER);
gl.shaderSource(fragShader, FSHADER_SOURCE);
gl.compileShader(fragShader);
//合并程序
var shaderProgram = gl.createProgram();
gl.attachShader(shaderProgram, vertShader);
gl.attachShader(shaderProgram, fragShader);
gl.linkProgram(shaderProgram);
gl.useProgram(shaderProgram);
//获取坐标点
var a_Position = gl.getAttribLocation(shaderProgram, 'a_Position');
if (a_Position < 0) {
console.log('Failed to get the storage location of a_Position');
return;
}
var n = initBuffers(gl, shaderProgram);
if (n < 0) {
console.log('Failed to set the positions');
return;
}
opt(gl, shaderProgram);
// 清除指定<画布>的颜色
gl.clearColor(0.0, 0.0, 0.0, 1.0);
// 清空
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.TRIANGLES, 0, n);
}
function opt(gl, program) {
// 旋转角度
var ANGLE = 90.0;
var radian = Math.PI * ANGLE / 180.0;
var cosB = Math.cos(radian);
var sinB = Math.sin(radian);
var u_CosB = gl.getUniformLocation(program, 'u_CosB');
var u_sinB = gl.getUniformLocation(program, 'u_SinB');
gl.uniform1f(u_CosB, cosB);
gl.uniform1f(u_sinB, sinB);
}
function initBuffers(gl, shaderProgram) {
var vertices = new Float32Array([
0, 0.5, -0.5, -0.5, 0.5, -0.5
]);
var n = 3;//点的个数
//创建缓冲区对象
var vertexBuffer = gl.createBuffer();
if (!vertexBuffer) {
console.log("Failed to create the butter object");
return -1;
}
//将缓冲区对象绑定到目标
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
//向缓冲区写入数据
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
//获取坐标点
var a_Position = gl.getAttribLocation(shaderProgram, 'a_Position');
//将缓冲区对象分配给a_Position变量
gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);
//连接a_Position变量与分配给它的缓冲区对象
gl.enableVertexAttribArray(a_Position);
return n;
}
main();
script>缩放
1、关键点说明
顶点着色器需要加上 uniform mat4 u_xformMatrix, 存储缩放因子的坐标矢量。
顶点坐标位置 ： gl_Position = u_xformMatrix * a_Position
缩放API ： gl.uniformMatrix4fv(u_xformMatrix, false, xformMatrix);
- u_xformMatrix ： 缩放因子
- xformMatrix ： 原始坐标
2、demo
- JavaScript
<script>
function main() {
//顶点着色器程序
var VSHADER_SOURCE =
'attribute vec4 a_Position;\n' +
'uniform mat4 u_xformMatrix;\n' +
'void main() {\n' +
' gl_Position = u_xformMatrix * a_Position;\n' +
'}\n';
//片元着色器程序
var FSHADER_SOURCE =
'void main() {\n' +
' gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n' +
'}\n';
var Tx = 0.5, Ty = 0.5, Tz = 0.0;
//获取canvas元素
var canvas = document.getElementById('canvas');
//获取绘制二维上下文
var gl = canvas.getContext('webgl');
if (!gl) {
console.log("Failed");
return;
}
//编译着色器
var vertShader = gl.createShader(gl.VERTEX_SHADER);
gl.shaderSource(vertShader, VSHADER_SOURCE);
gl.compileShader(vertShader);
var fragShader = gl.createShader(gl.FRAGMENT_SHADER);
gl.shaderSource(fragShader, FSHADER_SOURCE);
gl.compileShader(fragShader);
//合并程序
var shaderProgram = gl.createProgram();
gl.attachShader(shaderProgram, vertShader);
gl.attachShader(shaderProgram, fragShader);
gl.linkProgram(shaderProgram);
gl.useProgram(shaderProgram);
//获取坐标点
var a_Position = gl.getAttribLocation(shaderProgram, 'a_Position');
if (a_Position < 0) {
console.log('Failed to get the storage location of a_Position');
return;
}
var n = initBuffers(gl, shaderProgram);
if (n < 0) {
console.log('Failed to set the positions');
return;
}
opt(gl, shaderProgram);
// 清除指定<画布>的颜色
gl.clearColor(0, 0, 0, 1);
// 清空
gl.clear(gl.COLOR_BUFFER_BIT);
// Draw the rectangle
gl.drawArrays(gl.TRIANGLES, 0, n);
}
// 缩放
function opt(gl, program) {
// 缩放因子
var Sx = 1.0, Sy = 1.5, Sz = 1.0;
var xformMatrix = new Float32Array([
Sx, 0.0, 0.0, 0.0,
0.0, Sy, 0.0, 0.0,
0.0, 0.0, Sz, 0.0,
0.0, 0.0, 0.0, 1.0
]);
var u_xformMatrix = gl.getUniformLocation(program, 'u_xformMatrix');
gl.uniformMatrix4fv(u_xformMatrix, false, xformMatrix);
}
// 构建缓冲区
function initBuffers(gl, shaderProgram) {
var vertices = new Float32Array([
0, 0.5, -0.5, -0.5, 0.5, -0.5
]);
var n = 3;//点的个数
//创建缓冲区对象
var vertexBuffer = gl.createBuffer();
if (!vertexBuffer) {
console.log("Failed to create the butter object");
return -1;
}
//将缓冲区对象绑定到目标
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
//向缓冲区写入数据
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
//获取坐标点
var a_Position = gl.getAttribLocation(shaderProgram, 'a_Position');
//将缓冲区对象分配给a_Position变量
gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);
//连接a_Position变量与分配给它的缓冲区对象
gl.enableVertexAttribArray(a_Position);
return n;
}
// 主方法调用
main();
script>