从 Shadershop 函数到 glsl 函数的问题

Question

和有点关系。仅以上回答不作任何解释

我尝试的是：

其中 SineV 为：

SineH 是：

这是我目前拥有的：

#ifdef GL_ES
precision mediump float;
#endif

float scale = 5.0;


uniform vec2 u_resolution;

float sineV(float x) {
    x *= scale;
    return  (sin( x / 0.18 ) + sin( (x - -1.0) / 0.35 ) + 0.25);
}

float sineH(float x) {
    x *= scale;
    return (sin( (x - 0.18) / 0.37 ) + sin( ((x - 0.18) - -0.31) / 0.45 ) + -0.59) * 0.75 + 0.1;
}

mat2 inverse(mat2 m) {
    float det_m = m[0][0]*m[1][1] - m[0][1]*m[1][0];
    mat2  inv_m = mat2(m[1][1], -m[0][1], -m[1][0], m[0][0]) / det_m;
    return inv_m;
}



void main() {

    mat2 m = mat2(0.0, -1.0,
                  1.0, 0.0);

    vec2 st = gl_FragCoord.xy / u_resolution.xy;
    float x1 = st.x;
    float x2 = st.y;

    vec2  x1x2 = inverse(m) * vec2(x1, x2);

    vec2 tmp = m * x1x2;

    float x = sineV(x1x2.x - x1x2.y) + sineH(tmp.x - tmp.y);

    vec3 color = vec3( x, x, abs(x) );
    gl_FragColor = vec4(color, 1.0);
}

但我到了一个地步，它只是猜测和反复试验。希望有人能帮忙。

Answer 1

shadershop 中的矩阵将输入元组 (x1, x2) 转换为 (u, v) 坐标。片段着色器针对每个片段执行，每个片段关联到不同的 (u, v) 坐标。您必须计算与片段的实际 (u, v) 坐标对应的 x1 和 x2。所以你必须使用逆矩阵：

(u, v)  = m * (x1, x2)
(x1, x2 = inverse(m) * (u, v)

着色器必须对 f(x1) 的结果和 f(x2) 的结果求和：

x = f(x1) + f(x2)

对应的glsl代码为：

vec2  x1x2 = inverse(m) * st.xy;
float x    = sineH(x1x2.x) + sineV(x1x2.y);

x到白色、蓝色和黑色的映射可以通过经验公式来实现（我通过反复试验发现的）：

vec3 color = vec3(x, x, abs(x));

完整的着色器代码见示例（注意，结果被拉伸到 canvas）：

(function loadscene() {    

var canvas, gl, vp_size, prog, bufObj = {};

function initScene() {

    canvas = document.getElementById( "ogl-canvas");
    gl = canvas.getContext( "experimental-webgl" );
    if ( !gl )
      return;

    progDraw = gl.createProgram();
    for (let i = 0; i < 2; ++i) {
        let source = document.getElementById(i==0 ? "draw-shader-vs" : "draw-shader-fs").text;
        let shaderObj = gl.createShader(i==0 ? gl.VERTEX_SHADER : gl.FRAGMENT_SHADER);
        gl.shaderSource(shaderObj, source);
        gl.compileShader(shaderObj);
        let status = gl.getShaderParameter(shaderObj, gl.COMPILE_STATUS);
        if (!status) alert(gl.getShaderInfoLog(shaderObj));
        gl.attachShader(progDraw, shaderObj);
        gl.linkProgram(progDraw);
    }
    status = gl.getProgramParameter(progDraw, gl.LINK_STATUS);
    if ( !status ) alert(gl.getProgramInfoLog(progDraw));
    progDraw.inPos = gl.getAttribLocation(progDraw, "inPos");
    progDraw.u_resolution = gl.getUniformLocation(progDraw, "u_resolution");
    gl.useProgram(progDraw);

    var pos = [ -1, -1, 1, -1, 1, 1, -1, 1 ];
    var inx = [ 0, 1, 2, 0, 2, 3 ];
    bufObj.pos = gl.createBuffer();
    gl.bindBuffer( gl.ARRAY_BUFFER, bufObj.pos );
    gl.bufferData( gl.ARRAY_BUFFER, new Float32Array( pos ), gl.STATIC_DRAW );
    bufObj.inx = gl.createBuffer();
    bufObj.inx.len = inx.length;
    gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, bufObj.inx );
    gl.bufferData( gl.ELEMENT_ARRAY_BUFFER, new Uint16Array( inx ), gl.STATIC_DRAW );
    gl.enableVertexAttribArray( progDraw.inPos );
    gl.vertexAttribPointer( progDraw.inPos, 2, gl.FLOAT, false, 0, 0 ); 
    
    gl.enable( gl.DEPTH_TEST );
    gl.clearColor( 0.0, 0.0, 0.0, 1.0 );

    window.onresize = resize;
    resize();
    requestAnimationFrame(render);
}

function resize() {
    vp_size = [window.innerWidth, window.innerHeight];
    //vp_size = [256, 256]
    canvas.width = vp_size[0];
    canvas.height = vp_size[1];
}

function render(deltaMS) {

    gl.viewport( 0, 0, canvas.width, canvas.height );
    gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT );
   
    gl.uniform2f(progDraw.u_resolution, canvas.width, canvas.height);
    gl.drawElements( gl.TRIANGLES, bufObj.inx.len, gl.UNSIGNED_SHORT, 0 );
    
    requestAnimationFrame(render);
}  

initScene();

})();

<script id="draw-shader-vs" type="x-shader/x-vertex">
precision mediump float;

attribute vec2 inPos;

varying vec2 ndcPos;

void main()
{
    gl_Position = vec4( inPos.xy, 0.0, 1.0 );
}
</script>

<script id="draw-shader-fs" type="x-shader/x-fragment">
precision mediump float;

uniform vec2  u_resolution;

float scale = 5.0;

float sineV(float x) {
    x *= scale;
    return  (sin( x / 0.18 ) + sin( (x - -1.0) / 0.35 ) + 0.25);
}

float sineH(float x) {
    x *= scale;
    return (sin( (x - 0.18) / 0.37 ) + sin( ((x - 0.18) - -0.31) / 0.45 ) + -0.59) * 0.75 + 0.1;
}

mat2 inverse(mat2 m) {
    float det_m = m[0][0]*m[1][1] - m[0][1]*m[1][0];
    mat2  inv_m = mat2(m[1][1], -m[0][1], -m[1][0], m[0][0]) / det_m;
    return inv_m;
}

void main()
{
    vec2  st     = 2.0 * gl_FragCoord.xy / u_resolution.xy - 1.0;
    mat2  m      = mat2(0.0, -1.0, 1.0, 0.0);
    vec2  x1x2   = inverse(m) * st.xy;
    float x      = sineH(x1x2.x) + sineV(x1x2.y);

    vec3 color   = vec3(x, x, abs(x));
    gl_FragColor = vec4(color, 1.0);
}
</script>

<canvas id="ogl-canvas" style="border: none"></canvas>

从 Shadershop 函数到 glsl 函数的问题

Problem going from Shadershop functions to glsl functions

glsl

shader

glsles