Question

triangle image

所以，这是尝试在不使用矩阵变换的情况下旋转三角形的结果，我的赋值需要将浮点数传递给顶点着色器，然后在着色器中进行变换数学运算。

我使用

旋转顶点

    uPosition.x = (cos(fRotation)*uPosition.x)-(sin(fRotation)*uPosition.y);
    uPosition.y = (cos(fRotation)*uPosition.y)+(sin(fRotation)*uPosition.x);

从我在任何地方看到的与矩阵执行相同的数学运算并且我不想使用矩阵执行它。

以下完整代码 Webgl代码：

var gl;
var points;
var colours;
var fRotation;
var program;

window.onload = function init()
{
    canvas = document.getElementById( "gl-canvas" );

    gl = WebGLUtils.setupWebGL( canvas );
    if ( !gl ) { alert( "WebGL isn't available" ); }

    fRotation = 1;

    //
    //  Initialize our data for the Triangle
    //

    // First, initialize the corners of our triangle with three points.
    points = [
        vec2( 0, 0.6 ),
        vec2( -0.5, -0.3 ),
        vec2( 0.5, -0.3 )
    ];

    //Next, initialize the colours for each corner in Red,Green,Blue
    colours = [
        vec3( 1, 0,0 ),
        vec3( 0, 1,0 ),
        vec3( 0, 0,1 )
    ];

    //
    //  Configure WebGL
    //
    gl.viewport( 0, 0, canvas.width, canvas.height );
    gl.clearColor( 0.0, 0.0, 0.0, 1.0 );

    //  Load shaders and initialize attribute buffers
    program = initShaders( gl, vBasicShaderCode,
                               fBasicShaderCode );
    gl.useProgram( program );

    // Load the positional data into the GPU
    var posBufferId = gl.createBuffer();
    gl.bindBuffer( gl.ARRAY_BUFFER, posBufferId );
    gl.bufferData( gl.ARRAY_BUFFER, flatten(points), gl.STATIC_DRAW );

    // Associate out shader variables with our data buffer
    var vPos = gl.getAttribLocation( program, "aPosition" );
    gl.vertexAttribPointer( vPos, 2, gl.FLOAT, false, 0, 0 );
    gl.enableVertexAttribArray( vPos );

    // Load the colour data into the GPU
    var colBufferId = gl.createBuffer();
    gl.bindBuffer( gl.ARRAY_BUFFER, colBufferId );
    gl.bufferData( gl.ARRAY_BUFFER, flatten(colours), gl.STATIC_DRAW );

    // Associate out shader variables with our data buffer
    var vCol = gl.getAttribLocation( program, "aColour" );
    gl.vertexAttribPointer( vCol, 3, gl.FLOAT, false, 0, 0 );
    gl.enableVertexAttribArray( vCol );


    render();
};


function render()
{

    gl.uniform1f(gl.getUniformLocation(program, "fRotation"), fRotation );
    gl.clear( gl.COLOR_BUFFER_BIT );
    gl.drawArrays( gl.TRIANGLES, 0, 3 ); //Draw a single triangle (3 points)

    fRotation += 0.1;
}

顶点着色器

var vBasicShaderCode  =`
attribute vec2 aPosition; 
attribute vec3 aColour;
uniform float fRotation;
varying vec3 vColour;


void 
main() 
{
    vColour=aColour;

    vec2 uPosition = vec2(0.0,0.0);

    //translate

    uPosition.x = aPosition.x;
    uPosition.y = aPosition.y;

    uPosition.x = (cos(fRotation)*uPosition.x)-(sin(fRotation)*uPosition.y);
    uPosition.y = (cos(fRotation)*uPosition.y)+(sin(fRotation)*uPosition.x);

    gl_Position = vec4(uPosition.x,uPosition.y,0.0,1.0); 
}`;

Answer 1

在使用着色器代码计算uPosition.x之前，您正在更改着色器代码中的变量uPosition.y。

uPosition.x = (cos(fRotation)*uPosition.x)-(sin(fRotation)*uPosition.y);
uPosition.y = (cos(fRotation)*uPosition.y)+(sin(fRotation)*uPosition.x);

使用属性aPosition代替计算uPosition：

uPosition.x = (cos(fRotation)*aPosition.x)-(sin(fRotation)*aPosition.y);
uPosition.y = (cos(fRotation)*aPosition.y)+(sin(fRotation)*aPosition.x);

webgl在顶点着色器中旋转三角形而不使用变换矩阵

1 个答案: