过去一周来，我一直在努力尝试理解WebGL中的旋转形状。我正在绘制从它们自己的函数调用的3个形状。函数的基本结构有点像这样：
function drawShape(vertices) {
var a = vertices.length / 2;
gl.bindBuffer(gl.ARRAY_BUFFER, bufferId);
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
var vPosition = gl.getAttribLocation(program, "vPosition");
gl.vertexAttribPointer(vPosition, 2, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(vPosition);
gl.drawArrays(gl.TRIANGLE_FAN, 0, a);
}
现在我已经渲染了每个形状函数被调用的地方。有点像这样：
function render() {
angleInRadians += 0.1;
gl.viewport(0, 0, canvas.width, canvas.height);
gl.clearColor(0, 0, 0, 1);
gl.clear(gl.COLOR_BUFFER_BIT);
drawShape1();
drawShape2();
matrix = mat.rotation(angleInRadians);
gl.uniformMatrix3fv(matrixLocation, false, matrix);
requestAnimFrame( render );
}
旋转功能为：
rotation: function(angle) {
var a = Math.cos(angle);
var b = Math.sin(angle);
return [
a,-b, 0,
b, a, 0,
0, 0, 1,
];
},
我一直试图从3个形状中仅旋转1个。我尝试在函数drawArrays之前使用匀速3fv来绘制要旋转的形状，但所有形状都会随之旋转。如何只旋转一种形状？
答案 0 :(得分：2)
首先，通常更常见的是在初始化时上传顶点数据，然后在渲染时使用它。您发布的代码是在渲染时上传顶点数据。在初始化时间而不是渲染时间查找属性位置也将更为常见。
换句话说，你有这个
function drawShape(vertices) {
var a = vertices.length / 2;
gl.bindBuffer(gl.ARRAY_BUFFER, bufferId);
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
var vPosition = gl.getAttribLocation(program, "vPosition");
gl.vertexAttribPointer(vPosition, 2, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(vPosition);
gl.drawArrays(gl.TRIANGLE_FAN, 0, a);
}
但是做这样的事情会更常见
const attribs = {
vPosition: gl.getAttribLocation(program, "vPosition"),
};
const shape = createShape(vertices);
...
drawShape(attribs, shape);
function createShape(vertices) {
const bufferId = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, bufferId);
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
return {
bufferId,
numVertices: vertices.length / 2,
};
}
function drawShape(attribs, shape) {
gl.bindBuffer(gl.ARRAY_BUFFER, shape.bufferId);
gl.vertexAttribPointer(attribs.vPosition, 2, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(attrib.vPosition);
gl.drawArrays(gl.TRIANGLE_FAN, 0, shape.numVertices);
}
或类似的内容。
您还可能会在初始化时查找制服，然后传递制服并将其设置在drawShape内（或不设置在内）。通常，关键是通常在初始化时间调用gl.bufferData，gl.getUniformLocation和gl.getAttribLocation
接下来，您需要每个形状设置一次制服。
matrix = mat.rotation(angleInRadiansForShape1);
gl.uniformMatrix3fv(matrixLocation, false, matrix);
drawShape1();
matrix = mat.rotation(angleInRadiansForShape2);
gl.uniformMatrix3fv(matrixLocation, false, matrix);
drawShape2();
但是您不仅需要添加旋转，否则所有形状都将出现在同一位置。
旋转矩阵绕原点（0,0）旋转。如果要围绕其他点旋转，请平移顶点。您可以通过将旋转矩阵乘以转换矩阵来实现。
由于它需要一个数学库并且每个库的使用方法都不相同，因此很难说明如何做到这一点。
This article介绍了如何使用本文中创建的函数对矩阵求和。
要移动旋转点，请执行此操作。
var matrix = m3.projection(gl.canvas.clientWidth, gl.canvas.clientHeight);
matrix = m3.translate(matrix, whereToDrawX, whereToDrawY);
matrix = m3.rotate(matrix, angleToRotate);
matrix = m3.translate(matrix, offsetForRotationX, offsetForRotationY);
我通常从下至上阅读该书，
m3.translate(matrix, offsetForRotationX, offsetForRotationY) =平移顶点，以便它们的原点是我们要旋转的位置。例如，如果我们有一个框，框的范围从0到10，向下为0到20，并且我们想在右下角旋转，那么我们需要将右下角移到0,0，这意味着我们需要平移-10，-20所以右下角在原点。
m3.rotate(matrix, angleToRotate) =旋转
m3.translate(matrix, whereToDrawX, whereToDrawY) =将其翻译到我们实际希望绘制的位置。
m3.projection(gl.canvas.clientWidth, gl.canvas.clientHeight) =从像素转换为剪辑空间
示例：
"use strict";
function main() {
// Get A WebGL context
/** @type {HTMLCanvasElement} */
var canvas = document.getElementById("canvas");
var gl = canvas.getContext("webgl");
if (!gl) {
return;
}
// setup GLSL program
var program = webglUtils.createProgramFromScripts(gl, ["2d-vertex-shader", "2d-fragment-shader"]);
// look up where the vertex data needs to go.
var positionLocation = gl.getAttribLocation(program, "a_position");
// lookup uniforms
var colorLocation = gl.getUniformLocation(program, "u_color");
var matrixLocation = gl.getUniformLocation(program, "u_matrix");
// Create a buffer to put positions in
var positionBuffer = gl.createBuffer();
// Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = positionBuffer)
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Put geometry data into buffer
setGeometry(gl);
const shapes = [
{
translation: [50, 75],
scale: [0.5, 0.5],
rotationOffset: [0, 0], // top left corner of F
angleInRadians: 0,
color: [1, 0, 0, 1], // red
},
{
translation: [100, 75],
scale: [0.5, 0.5],
rotationOffset: [-50, -75], // center of F
angleInRadians: 0,
color: [0, 1, 0, 1], // green
},
{
translation: [150, 75],
scale: [0.5, 0.5],
rotationOffset: [0, -150], // bottom left corner of F
angleInRadians: 0,
color: [0, 0, 1, 1], // blue
},
{
translation: [200, 75],
scale: [0.5, 0.5],
rotationOffset: [-100, 0], // top right corner of F
angleInRadians: 0,
color: [1, 0, 1, 1], // magenta
},
];
requestAnimationFrame(drawScene);
// Draw the scene.
function drawScene(time) {
time *= 0.001; // seconds
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.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT);
// draw a single black line to make the pivot clearer
gl.enable(gl.SCISSOR_TEST);
gl.scissor(0, 75, 300, 1);
gl.clearColor(0, 0, 0, 1);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.disable(gl.SCISSOR_TEST);
// Tell it to use our program (pair of shaders)
gl.useProgram(program);
// Turn on the attribute
gl.enableVertexAttribArray(positionLocation);
// Bind the position buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Tell the attribute how to get data out of positionBuffer (ARRAY_BUFFER)
var size = 2; // 2 components per iteration
var type = gl.FLOAT; // the data is 32bit floats
var normalize = false; // don't normalize the data
var stride = 0; // 0 = move forward size * sizeof(type) each iteration to get the next position
var offset = 0; // start at the beginning of the buffer
gl.vertexAttribPointer(
positionLocation, size, type, normalize, stride, offset);
for (const shape of shapes) {
shape.angleInRadians = time;
// set the color
gl.uniform4fv(colorLocation, shape.color);
// Compute the matrices
var matrix = m3.projection(gl.canvas.clientWidth, gl.canvas.clientHeight);
matrix = m3.translate(matrix, shape.translation[0], shape.translation[1]);
matrix = m3.scale(matrix, shape.scale[0], shape.scale[1]);
matrix = m3.rotate(matrix, shape.angleInRadians);
matrix = m3.translate(matrix, shape.rotationOffset[0], shape.rotationOffset[1]);
// Set the matrix.
gl.uniformMatrix3fv(matrixLocation, false, matrix);
// Draw the geometry.
var primitiveType = gl.TRIANGLES;
var offset = 0;
var count = 18; // 6 triangles in the 'F', 3 points per triangle
gl.drawArrays(primitiveType, offset, count);
}
requestAnimationFrame(drawScene);
}
}
var m3 = {
projection: function(width, height) {
// Note: This matrix flips the Y axis so that 0 is at the top.
return [
2 / width, 0, 0,
0, -2 / height, 0,
-1, 1, 1
];
},
identity: function() {
return [
1, 0, 0,
0, 1, 0,
0, 0, 1,
];
},
translation: function(tx, ty) {
return [
1, 0, 0,
0, 1, 0,
tx, ty, 1,
];
},
rotation: function(angleInRadians) {
var c = Math.cos(angleInRadians);
var s = Math.sin(angleInRadians);
return [
c,-s, 0,
s, c, 0,
0, 0, 1,
];
},
scaling: function(sx, sy) {
return [
sx, 0, 0,
0, sy, 0,
0, 0, 1,
];
},
multiply: function(a, b) {
var a00 = a[0 * 3 + 0];
var a01 = a[0 * 3 + 1];
var a02 = a[0 * 3 + 2];
var a10 = a[1 * 3 + 0];
var a11 = a[1 * 3 + 1];
var a12 = a[1 * 3 + 2];
var a20 = a[2 * 3 + 0];
var a21 = a[2 * 3 + 1];
var a22 = a[2 * 3 + 2];
var b00 = b[0 * 3 + 0];
var b01 = b[0 * 3 + 1];
var b02 = b[0 * 3 + 2];
var b10 = b[1 * 3 + 0];
var b11 = b[1 * 3 + 1];
var b12 = b[1 * 3 + 2];
var b20 = b[2 * 3 + 0];
var b21 = b[2 * 3 + 1];
var b22 = b[2 * 3 + 2];
return [
b00 * a00 + b01 * a10 + b02 * a20,
b00 * a01 + b01 * a11 + b02 * a21,
b00 * a02 + b01 * a12 + b02 * a22,
b10 * a00 + b11 * a10 + b12 * a20,
b10 * a01 + b11 * a11 + b12 * a21,
b10 * a02 + b11 * a12 + b12 * a22,
b20 * a00 + b21 * a10 + b22 * a20,
b20 * a01 + b21 * a11 + b22 * a21,
b20 * a02 + b21 * a12 + b22 * a22,
];
},
translate: function(m, tx, ty) {
return m3.multiply(m, m3.translation(tx, ty));
},
rotate: function(m, angleInRadians) {
return m3.multiply(m, m3.rotation(angleInRadians));
},
scale: function(m, sx, sy) {
return m3.multiply(m, m3.scaling(sx, sy));
},
};
// Fill the buffer with the values that define a letter 'F'.
function setGeometry(gl) {
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array([
// left column
0, 0,
30, 0,
0, 150,
0, 150,
30, 0,
30, 150,
// top rung
30, 0,
100, 0,
30, 30,
30, 30,
100, 0,
100, 30,
// middle rung
30, 60,
67, 60,
30, 90,
30, 90,
67, 60,
67, 90,
]),
gl.STATIC_DRAW);
}
main();<canvas id="canvas"></canvas>
<!-- vertex shader -->
<script id="2d-vertex-shader" type="x-shader/x-vertex">
attribute vec2 a_position;
uniform mat3 u_matrix;
void main() {
// Multiply the position by the matrix.
gl_Position = vec4((u_matrix * vec3(a_position, 1)).xy, 0, 1);
}
</script>
<!-- fragment shader -->
<script id="2d-fragment-shader" type="x-shader/x-fragment">
precision mediump float;
uniform vec4 u_color;
void main() {
gl_FragColor = u_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 http://webglfundamentals.org/webgl/lessons/webgl-boilerplate.html
and http://webglfundamentals.org/webgl/lessons/webgl-resizing-the-canvas.html
for webgl-utils, m3, m4, and webgl-lessons-ui.
-->
<script src="https://webglfundamentals.org/webgl/resources/webgl-utils.js"></script>
如果您不想移动旋转中心，只需删除与rotationOffset相关的最后一步
"use strict";
function main() {
// Get A WebGL context
/** @type {HTMLCanvasElement} */
var canvas = document.getElementById("canvas");
var gl = canvas.getContext("webgl");
if (!gl) {
return;
}
// setup GLSL program
var program = webglUtils.createProgramFromScripts(gl, ["2d-vertex-shader", "2d-fragment-shader"]);
// look up where the vertex data needs to go.
var positionLocation = gl.getAttribLocation(program, "a_position");
// lookup uniforms
var colorLocation = gl.getUniformLocation(program, "u_color");
var matrixLocation = gl.getUniformLocation(program, "u_matrix");
// Create a buffer to put positions in
var positionBuffer = gl.createBuffer();
// Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = positionBuffer)
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Put geometry data into buffer
setGeometry(gl);
const shapes = [
{
translation: [50, 75],
scale: [0.5, 0.5],
rotationOffset: [0, 0], // top left corner of F
angleInRadians: 0,
color: [1, 0, 0, 1], // red
},
{
translation: [100, 75],
scale: [0.5, 0.5],
rotationOffset: [-50, -75], // center of F
angleInRadians: 0,
color: [0, 1, 0, 1], // green
},
{
translation: [150, 75],
scale: [0.5, 0.5],
rotationOffset: [0, -150], // bottom left corner of F
angleInRadians: 0,
color: [0, 0, 1, 1], // blue
},
{
translation: [200, 75],
scale: [0.5, 0.5],
rotationOffset: [-100, 0], // top right corner of F
angleInRadians: 0,
color: [1, 0, 1, 1], // magenta
},
];
requestAnimationFrame(drawScene);
// Draw the scene.
function drawScene(time) {
time *= 0.001; // seconds
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.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT);
// draw a single black line to make the pivot clearer
gl.enable(gl.SCISSOR_TEST);
gl.scissor(0, 75, 300, 1);
gl.clearColor(0, 0, 0, 1);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.disable(gl.SCISSOR_TEST);
// Tell it to use our program (pair of shaders)
gl.useProgram(program);
// Turn on the attribute
gl.enableVertexAttribArray(positionLocation);
// Bind the position buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Tell the attribute how to get data out of positionBuffer (ARRAY_BUFFER)
var size = 2; // 2 components per iteration
var type = gl.FLOAT; // the data is 32bit floats
var normalize = false; // don't normalize the data
var stride = 0; // 0 = move forward size * sizeof(type) each iteration to get the next position
var offset = 0; // start at the beginning of the buffer
gl.vertexAttribPointer(
positionLocation, size, type, normalize, stride, offset);
for (const shape of shapes) {
shape.angleInRadians = time;
// set the color
gl.uniform4fv(colorLocation, shape.color);
// Compute the matrices
var matrix = m3.projection(gl.canvas.clientWidth, gl.canvas.clientHeight);
matrix = m3.translate(matrix, shape.translation[0], shape.translation[1]);
matrix = m3.scale(matrix, shape.scale[0], shape.scale[1]);
matrix = m3.rotate(matrix, shape.angleInRadians);
//matrix = m3.translate(matrix, shape.rotationOffset[0], shape.rotationOffset[1]);
// Set the matrix.
gl.uniformMatrix3fv(matrixLocation, false, matrix);
// Draw the geometry.
var primitiveType = gl.TRIANGLES;
var offset = 0;
var count = 18; // 6 triangles in the 'F', 3 points per triangle
gl.drawArrays(primitiveType, offset, count);
}
requestAnimationFrame(drawScene);
}
}
var m3 = {
projection: function(width, height) {
// Note: This matrix flips the Y axis so that 0 is at the top.
return [
2 / width, 0, 0,
0, -2 / height, 0,
-1, 1, 1
];
},
identity: function() {
return [
1, 0, 0,
0, 1, 0,
0, 0, 1,
];
},
translation: function(tx, ty) {
return [
1, 0, 0,
0, 1, 0,
tx, ty, 1,
];
},
rotation: function(angleInRadians) {
var c = Math.cos(angleInRadians);
var s = Math.sin(angleInRadians);
return [
c,-s, 0,
s, c, 0,
0, 0, 1,
];
},
scaling: function(sx, sy) {
return [
sx, 0, 0,
0, sy, 0,
0, 0, 1,
];
},
multiply: function(a, b) {
var a00 = a[0 * 3 + 0];
var a01 = a[0 * 3 + 1];
var a02 = a[0 * 3 + 2];
var a10 = a[1 * 3 + 0];
var a11 = a[1 * 3 + 1];
var a12 = a[1 * 3 + 2];
var a20 = a[2 * 3 + 0];
var a21 = a[2 * 3 + 1];
var a22 = a[2 * 3 + 2];
var b00 = b[0 * 3 + 0];
var b01 = b[0 * 3 + 1];
var b02 = b[0 * 3 + 2];
var b10 = b[1 * 3 + 0];
var b11 = b[1 * 3 + 1];
var b12 = b[1 * 3 + 2];
var b20 = b[2 * 3 + 0];
var b21 = b[2 * 3 + 1];
var b22 = b[2 * 3 + 2];
return [
b00 * a00 + b01 * a10 + b02 * a20,
b00 * a01 + b01 * a11 + b02 * a21,
b00 * a02 + b01 * a12 + b02 * a22,
b10 * a00 + b11 * a10 + b12 * a20,
b10 * a01 + b11 * a11 + b12 * a21,
b10 * a02 + b11 * a12 + b12 * a22,
b20 * a00 + b21 * a10 + b22 * a20,
b20 * a01 + b21 * a11 + b22 * a21,
b20 * a02 + b21 * a12 + b22 * a22,
];
},
translate: function(m, tx, ty) {
return m3.multiply(m, m3.translation(tx, ty));
},
rotate: function(m, angleInRadians) {
return m3.multiply(m, m3.rotation(angleInRadians));
},
scale: function(m, sx, sy) {
return m3.multiply(m, m3.scaling(sx, sy));
},
};
// Fill the buffer with the values that define a letter 'F'.
function setGeometry(gl) {
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array([
// left column
0, 0,
30, 0,
0, 150,
0, 150,
30, 0,
30, 150,
// top rung
30, 0,
100, 0,
30, 30,
30, 30,
100, 0,
100, 30,
// middle rung
30, 60,
67, 60,
30, 90,
30, 90,
67, 60,
67, 90,
]),
gl.STATIC_DRAW);
}
main();<canvas id="canvas"></canvas>
<!-- vertex shader -->
<script id="2d-vertex-shader" type="x-shader/x-vertex">
attribute vec2 a_position;
uniform mat3 u_matrix;
void main() {
// Multiply the position by the matrix.
gl_Position = vec4((u_matrix * vec3(a_position, 1)).xy, 0, 1);
}
</script>
<!-- fragment shader -->
<script id="2d-fragment-shader" type="x-shader/x-fragment">
precision mediump float;
uniform vec4 u_color;
void main() {
gl_FragColor = u_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 http://webglfundamentals.org/webgl/lessons/webgl-boilerplate.html
and http://webglfundamentals.org/webgl/lessons/webgl-resizing-the-canvas.html
for webgl-utils, m3, m4, and webgl-lessons-ui.
-->
<script src="https://webglfundamentals.org/webgl/resources/webgl-utils.js"></script>
您可能还会发现this article有用
答案 1 :(得分：1)
您必须为每个形状设置一个单独的旋转矩阵（模型矩阵）。为每个形状定义一个单独的角度：
例如
var angleShape1 = 0.0;
var angleShape2 = 0.0;
计算每种形状的旋转矩阵并设置统一变量，在绘制形状之前：
function render() {
gl.viewport(0, 0, canvas.width, canvas.height);
gl.clearColor(0, 0, 0, 1);
gl.clear(gl.COLOR_BUFFER_BIT);
matrix1 = mat.rotation(angleShape1);
gl.uniformMatrix3fv(matrixLocation, false, matrix1);
drawShape1();
matrix2 = mat.rotation(angleShape2);
gl.uniformMatrix3fv(matrixLocation, false, matrix2);
drawShape2();
angleShape1 += 0.1;
angleShape2 += 0.2;
requestAnimFrame( render );
}
这将导致形状以不同的模型转换和单独的方向进行渲染。