在WebGL中旋转三角形

分类：编程问答

如何解决在WebGL中旋转三角形

我正在尝试渲染3D旋转三角形，已经进行了所有必要的更改，但是我的三角形变形了（看起来不像三角形）。你们知道我在这里想念吗？

编辑：我已经附加了输出，是的，我尝试过处理顶点，但是它并没有太大作用（因为它不会形成三角形）

var canvas;
var gl;

var NumVertices  = 12;

var points = [];
var colors = [];

var xAxis = 0;
var yAxis = 1;
var zAxis = 2;

var axis = 0;
var theta = [ 0,0 ];

var thetaLoc;

var vertices = [
    vec3(0.5,-0.2722,0.2886),vec3(0.0,-0.5773),vec3(-0.5,vec3(0.5,-0.5443,0.0)
]

var vertexColors = [
    [ 0.0,0.0,1.0 ],// black
    [ 1.0,// red
    [ 1.0,1.0,// yellow
    [ 0.0,1.0 ]  // green

];

window.onload = function init()
{
    canvas = document.getElementById( "gl-canvas" );
    
    gl = WebGLUtils.setupWebGL( canvas );
    if ( !gl ) { alert( "WebGL isn't available" ); }

    colorCube(); //change this name to pyramid

    gl.viewport( 0,canvas.width,canvas.height );
    gl.clearColor( 1.0,1.0 );
    
    gl.enable(gl.DEPTH_TEST);


    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 );
    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,3,0 );
    gl.enableVertexAttribArray( vPosition );

    thetaLoc = gl.getUniformLocation(program,"theta"); 
  
    
    document.getElementById( "xButton" ).onclick = function () {
        axis = xAxis;
    };
    document.getElementById( "yButton" ).onclick = function () {
        axis = yAxis;
    };
    document.getElementById( "zButton" ).onclick = function () {
        axis = zAxis;
    };
        
    render();
}

function colorCube()
{
    quad( 0,1,2 );
    quad( 3,0 );
    quad( 0,2 );
    quad( 0,2,3 );

}

function quad(a,b,c) 
{

    var indices = [ a,c];

    for ( var i = 0; i < indices.length; ++i ) {
        points.push( vertices[indices[i]] );

        colors.push(vertexColors[a]);
        
    }
}

function render()
{
    gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    theta[axis] += 2.0;
    gl.uniform3fv(thetaLoc,theta);

    gl.drawArrays( gl.TRIANGLES,NumVertices );

    requestAnimFrame( render );
}
<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>

<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,c.x,s.x,-s.x,1.0 );

    mat4 ry = mat4( c.y,-s.y,s.y,c.y,1.0 );


    mat4 rz = mat4( c.z,-s.z,s.z,c.z,1.0 );

    fColor = vColor;
    gl_Position = rz * ry * rx * vPosition;
} 
</script>

<script id="fragment-shader" type="x-shader/x-fragment">

precision mediump float;
   
varying vec4 fColor;

void
main()
{
    gl_FragColor = fColor;
}
</script>


<script src="https://esangel.github.io/WebGL/Common/webgl-utils.js"></script>
<script src="https://esangel.github.io/WebGL/Common/initShaders.js"></script>
<script src="https://esangel.github.io/WebGL/Common/MV.js"></script>

--------------------------------输出-------------- ------------- 这是我的输出的图片，它在所有轴上旋转，但没有3d三角形的形状

解决方法

我认为您在colorCube中有不好的索引

我将其更改为此

function colorCube()
{
    quad( 0,1,2 ); // bottom
    quad( 1,3 ); // side0
    quad( 1,2,3 ); // side1
    quad( 2,3 ); // side3

}

而且似乎可行。

我还改变了它为面部选择颜色的方式，从而使每个三角形成为下一个颜色。

function quad(a,b,c) 
{

    var indices = [ a,c];
    var ndx = points.length % vertexColors.length;
    for ( var i = 0; i < indices.length; ++i ) {
        points.push( vertices[indices[i]] );

        colors.push(vertexColors[ndx]);
        
    }
}

似乎可以正常工作。

var canvas;
var gl;

var NumVertices  = 12;

var points = [];
var colors = [];

var xAxis = 0;
var yAxis = 1;
var zAxis = 2;

var axis = 0;
var theta = [ 0,0 ];

var thetaLoc;

var vertices = [
    vec3(0.5,-0.2722,0.2886),vec3(0.0,-0.5773),vec3(-0.5,vec3(0.5,-0.5443,0.0)
]

var vertexColors = [
    [ 0.0,0.0,1.0 ],// black
    [ 1.0,// red
    [ 1.0,1.0,// yellow
    [ 0.0,1.0 ]  // green

];

window.onload = function init()
{
    canvas = document.getElementById( "gl-canvas" );
    
    gl = WebGLUtils.setupWebGL( canvas );
    if ( !gl ) { alert( "WebGL isn't available" ); }

    colorCube(); //change this name to pyramid

    gl.viewport( 0,canvas.width,canvas.height );
    gl.clearColor( 1.0,1.0 );
    
    gl.enable(gl.DEPTH_TEST);


    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 );
    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,3,0 );
    gl.enableVertexAttribArray( vPosition );

    thetaLoc = gl.getUniformLocation(program,"theta"); 
  
    
    document.getElementById( "xButton" ).onclick = function () {
        axis = xAxis;
    };
    document.getElementById( "yButton" ).onclick = function () {
        axis = yAxis;
    };
    document.getElementById( "zButton" ).onclick = function () {
        axis = zAxis;
    };
        
    render();
}

function colorCube()
{
    quad( 0,3 ); // side3

}

function quad(a,c];
    var ndx = points.length % vertexColors.length;
    for ( var i = 0; i < indices.length; ++i ) {
        points.push( vertices[indices[i]] );

        colors.push(vertexColors[ndx]);
        
    }
}

function render()
{
    gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    theta[axis] += 2.0;
    gl.uniform3fv(thetaLoc,theta);

    gl.drawArrays( gl.TRIANGLES,NumVertices );

    requestAnimFrame( render );
}
<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>

<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,c.x,s.x,-s.x,1.0 );

    mat4 ry = mat4( c.y,-s.y,s.y,c.y,1.0 );


    mat4 rz = mat4( c.z,-s.z,s.z,c.z,1.0 );

    fColor = vColor;
    gl_Position = rz * ry * rx * vPosition;
} 
</script>

<script id="fragment-shader" type="x-shader/x-fragment">

precision mediump float;
   
varying vec4 fColor;

void
main()
{
    gl_FragColor = fColor;
}
</script>


<script src="https://esangel.github.io/WebGL/Common/webgl-utils.js"></script>
<script src="https://esangel.github.io/WebGL/Common/initShaders.js"></script>
<script src="https://esangel.github.io/WebGL/Common/MV.js"></script>

如果要使用透视3D而不是正交3D，则可以使用perspective matrix

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