我必须使用滑块来改变旋转方格的角度：
JS
"use strict";
var canvas;
var gl;
var direction = true;
var degrees = 0;
var NumVertices = 36;
var points = [];
var colors = [];
var xAxis = 0;
var yAxis = 1;
var zAxis = 2;
var axis = 0;
var theta = [ 0, 0, 0 ];
var thetaLoc;
window.onload = function init()
{
canvas = document.getElementById( "gl-canvas" );
gl = WebGLUtils.setupWebGL( canvas );
if ( !gl ) { alert( "WebGL isn't available" ); }
colorCube();
gl.viewport( 0, 0, canvas.width, canvas.height );
gl.clearColor( 1.0, 1.0, 1.0, 1.0 );
gl.enable(gl.DEPTH_TEST);
//
// Load shaders and initialize attribute buffers
//
var program = initShaders( gl, "vertex-shader", "fragment-shader" );
gl.useProgram( program );
var cBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, cBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(colors), gl.STATIC_DRAW );
var vColor = gl.getAttribLocation( program, "vColor" );
gl.vertexAttribPointer( vColor, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vColor );
var vBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, vBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(points), gl.STATIC_DRAW );
var vPosition = gl.getAttribLocation( program, "vPosition" );
gl.vertexAttribPointer( vPosition, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vPosition );
thetaLoc = gl.getUniformLocation(program, "theta");
//event listeners for buttons
document.getElementById( "xButton" ).onclick = function () {
axis = xAxis;
};
document.getElementById( "yButton" ).onclick = function () {
axis = yAxis;
};
document.getElementById( "zButton" ).onclick = function () {
axis = zAxis;
};
// Start or Stop
var btn = document.getElementsByTagName('input')[0];
btn.addEventListener('click', function() {
if (direction == true)
direction = false;
else
direction = true;
});
// SLIDER
document.getElementById("slide").onchange = function(){
degrees = parseInt(event.target.value, 10);
};
render();
}
function colorCube()
{
quad( 1, 0, 3, 2 );
quad( 2, 3, 7, 6 );
quad( 3, 0, 4, 7 );
quad( 6, 5, 1, 2 );
quad( 4, 5, 6, 7 );
quad( 5, 4, 0, 1 );
}
function quad(a, b, c, d)
{
var vertices = [
vec4( -0.5, -0.5, 0.5, 1.0 ),
vec4( -0.5, 0.5, 0.5, 1.0 ),
vec4( 0.5, 0.5, 0.5, 1.0 ),
vec4( 0.5, -0.5, 0.5, 1.0 ),
vec4( -0.5, -0.5, -0.5, 1.0 ),
vec4( -0.5, 0.5, -0.5, 1.0 ),
vec4( 0.5, 0.5, -0.5, 1.0 ),
vec4( 0.5, -0.5, -0.5, 1.0 )
];
var vertexColors = [
[ 0.0, 0.0, 0.0, 1.0 ], // black
[ 1.0, 0.0, 0.0, 1.0 ], // red
[ 1.0, 1.0, 0.0, 1.0 ], // yellow
[ 0.0, 1.0, 0.0, 1.0 ], // green
[ 0.0, 0.0, 1.0, 1.0 ], // blue
[ 1.0, 0.0, 1.0, 1.0 ], // magenta
[ 0.0, 1.0, 1.0, 1.0 ], // cyan
[ 1.0, 1.0, 1.0, 1.0 ] // white
];
// We need to parition the quad into two triangles in order for
// WebGL to be able to render it. In this case, we create two
// triangles from the quad indices
//vertex color assigned by the index of the vertex
var indices = [ a, b, c, a, c, d ];
for ( var i = 0; i < indices.length; ++i ) {
points.push( vertices[indices[i]] );
//colors.push( vertexColors[indices[i]] );
// for solid colored faces use
colors.push(vertexColors[a]);
}
}
function render()
{
gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
if (direction == false){
theta[axis] == degrees;
//theta[axis] = degrees;
}
else {
theta[axis] += 2.0;
}
/// How to control the rotation degree ?
gl.uniform3fv(thetaLoc, theta);
gl.drawArrays( gl.TRIANGLES, 0, NumVertices );
requestAnimFrame( render );
}
HTML
<!DOCTYPE html>
<html>
<script id="vertex-shader" type="x-shader/x-vertex">
attribute vec4 vPosition;
attribute vec4 vColor;
varying vec4 fColor;
uniform vec3 theta;
void main()
{
// Compute the sines and cosines of theta for each of
// the three axes in one computation.
vec3 angles = radians( theta );
vec3 c = cos( angles );
vec3 s = sin( angles );
// Remeber: thse matrices are column-major
mat4 rx = mat4( 1.0, 0.0, 0.0, 0.0,
0.0, c.x, s.x, 0.0,
0.0, -s.x, c.x, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 ry = mat4( c.y, 0.0, -s.y, 0.0,
0.0, 1.0, 0.0, 0.0,
s.y, 0.0, c.y, 0.0,
0.0, 0.0, 0.0, 1.0 );
mat4 rz = mat4( c.z, s.z, 0.0, 0.0,
-s.z, c.z, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0 );
fColor = vColor;
gl_Position = rz * ry * rx * vPosition;
gl_Position.z = -gl_Position.z;
}
</script>
<script id="fragment-shader" type="x-shader/x-fragment">
precision mediump float;
varying vec4 fColor;
void
main()
{
gl_FragColor = fColor;
}
</script>
<script type="text/javascript" src="../Common/webgl-utils.js"></script>
<script type="text/javascript" src="../Common/initShaders.js"></script>
<script type="text/javascript" src="../Common/MV.js"></script>
<script type="text/javascript" src="Exercise1_1.js"></script>
<body>
<canvas id="gl-canvas" width="512"" height="512">
Oops ... your browser doesn't support the HTML5 canvas element
</canvas>
<br/>
<button id= "xButton">Rotate X</button>
<button id= "yButton">Rotate Y</button>
<button id= "zButton">Rotate Z</button>
<input type="button" value="Start or Stop" />
<div>
Angle 0 <input id="slide" type="range"
min="0" max="10" step="1" value="1" />
10 </div>
</body>
</html>
当我单击按钮并重新开始旋转时，此方块必须停止，如果我再次单击它并且此任务有效。问题是我必须使用滑块更改角度，如果我删除最后一个if语句中的注释，它也会起作用。
问题是，如果我单击开始按钮然后我停止它，它会停在开始位置而不是最后/当前位置（如果我从if语句代码中删除注释，如果我离开，就会发生这种情况评论开始/停止效果不错但我无法改变角度。）
感谢您的帮助。
答案 0 :(得分：0)
所有的拳头，这一行是错误的theta[axis] == degrees;
如您所见，您有2x =，因此您将theta[axis]与degrees进行比较。这意味着这一行什么都不做。
如果按下按钮，您想要停止多维数据集的移动，如果再次按下该按钮则启动它，这就是您拥有变量direction的原因。
如果direction为true，则您的多维数据集必须移动，因此您的theta[axis]应该会增加。如果您的direction false您的多维数据集应保持不变，那么theta[axis]必须保持其值。
这样的事情：
// If cube is moving
if (direction == true) {
theta[axis] += 2.0;
}
// If no movement
else {
// Do nothing
// the theta[axis] stays the same
}
但是现在你的立方体以相同的速度旋转......
也许您希望您的立方体以degrees速度旋转。
因此，您应该将2.0的静态值更改为变量degrees
从滑块中获取其值。
"use strict";
var canvas;
var gl;
var direction = true;
var degrees = 1.0; // Slider starts from value 1.0 as it has value="1" on it
var NumVertices = 36;
var points = [];
var colors = [];
var xAxis = 0;
var yAxis = 1;
var zAxis = 2;
var axis = 0;
var theta = [ 0, 0, 0 ];
var thetaLoc;
window.onload = function init()
{
canvas = document.getElementById( "gl-canvas" );
gl = WebGLUtils.setupWebGL( canvas );
if ( !gl ) { alert( "WebGL isn't available" ); }
colorCube();
gl.viewport( 0, 0, canvas.width, canvas.height );
gl.clearColor( 1.0, 1.0, 1.0, 1.0 );
gl.enable(gl.DEPTH_TEST);
//
// Load shaders and initialize attribute buffers
//
var program = initShaders( gl, "vertex-shader", "fragment-shader" );
gl.useProgram( program );
var cBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, cBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(colors), gl.STATIC_DRAW );
var vColor = gl.getAttribLocation( program, "vColor" );
gl.vertexAttribPointer( vColor, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vColor );
var vBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, vBuffer );
gl.bufferData( gl.ARRAY_BUFFER, flatten(points), gl.STATIC_DRAW );
var vPosition = gl.getAttribLocation( program, "vPosition" );
gl.vertexAttribPointer( vPosition, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vPosition );
thetaLoc = gl.getUniformLocation(program, "theta");
//event listeners for buttons
document.getElementById( "xButton" ).onclick = function () {
axis = xAxis;
};
document.getElementById( "yButton" ).onclick = function () {
axis = yAxis;
};
document.getElementById( "zButton" ).onclick = function () {
axis = zAxis;
};
// Start or Stop
var btn = document.getElementsByTagName('input')[0];
btn.addEventListener('click', function() {
if (direction == true)
direction = false;
else
direction = true;
});
// SLIDER
document.getElementById("slide").onchange = function(){
// As this is an event of the slider,
// here inside the handler, the variable `this`
// points to the slider, so we can do `this.value`
// to get the slider's value
degrees = parseInt(this.value, 10);
};
render();
}
function colorCube()
{
quad( 1, 0, 3, 2 );
quad( 2, 3, 7, 6 );
quad( 3, 0, 4, 7 );
quad( 6, 5, 1, 2 );
quad( 4, 5, 6, 7 );
quad( 5, 4, 0, 1 );
}
function quad(a, b, c, d)
{
var vertices = [
vec4( -0.5, -0.5, 0.5, 1.0 ),
vec4( -0.5, 0.5, 0.5, 1.0 ),
vec4( 0.5, 0.5, 0.5, 1.0 ),
vec4( 0.5, -0.5, 0.5, 1.0 ),
vec4( -0.5, -0.5, -0.5, 1.0 ),
vec4( -0.5, 0.5, -0.5, 1.0 ),
vec4( 0.5, 0.5, -0.5, 1.0 ),
vec4( 0.5, -0.5, -0.5, 1.0 )
];
var vertexColors = [
[ 0.0, 0.0, 0.0, 1.0 ], // black
[ 1.0, 0.0, 0.0, 1.0 ], // red
[ 1.0, 1.0, 0.0, 1.0 ], // yellow
[ 0.0, 1.0, 0.0, 1.0 ], // green
[ 0.0, 0.0, 1.0, 1.0 ], // blue
[ 1.0, 0.0, 1.0, 1.0 ], // magenta
[ 0.0, 1.0, 1.0, 1.0 ], // cyan
[ 1.0, 1.0, 1.0, 1.0 ] // white
];
// We need to parition the quad into two triangles in order for
// WebGL to be able to render it. In this case, we create two
// triangles from the quad indices
//vertex color assigned by the index of the vertex
var indices = [ a, b, c, a, c, d ];
for ( var i = 0; i < indices.length; ++i ) {
points.push( vertices[indices[i]] );
//colors.push( vertexColors[indices[i]] );
// for solid colored faces use
colors.push(vertexColors[a]);
}
}
function render()
{
gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
if (direction != false){
theta[axis] += degrees;
// theta[axis] is increased by the degrees variable
// that is being updated with the value of the slider
// every time we slide the slider
}
// How to control the rotation degree ?
// With a nice slider! ...
gl.uniform3fv(thetaLoc, theta);
gl.drawArrays( gl.TRIANGLES, 0, NumVertices );
requestAnimFrame( render );
}