opengl-es - 带有柏林噪声的 GLSL 阴影

Question

所以我最近开始使用 WebGL，更具体地说是编写 GLSL 着色器，并且在为我的“水”着色器编写片段着色器时遇到了障碍，该着色器源自 this tutorial.

我想要实现的是对顶点着色器生成的波浪的阶梯式着色(卡通着色、单元格着色...)效果，但片段着色器似乎将波浪视为仍然是平面和整个网格绘制为一种纯色。

我在这里缺少什么？球体工作完美，但平坦的表面都被均匀地着色。如果我使用立方体，我也有同样的问题。立方体上的每个面都被独立着色，但整个面都被赋予了纯色。

现场

这就是我设置测试场景的方式。我有两个使用相同 Material 的网格 - 一个球体、一个平面和一个光源。



问题

如您所见，着色器在球体上按预期工作。
我为这个镜头启用了线框，以显示顶点着色器(柏林噪声)在平面上工作得很好。



但是当我关闭线框时，您可以看到片段着色器似乎在整个平面上均匀地接收相同级别的光，从而创建了这个......



旋转平面以面向光源将改变 Material 的颜色，但颜色会再次均匀地应用于平面的整个表面。


片段着色器

总而言之，它是脚本小子的荣耀哈哈。

uniform vec3 uMaterialColor;
uniform vec3 uDirLightPos;
uniform vec3 uDirLightColor;
uniform float uKd;
uniform float uBorder;
varying vec3 vNormal;
varying vec3 vViewPosition;

void main() {

    vec4 color;

    // compute direction to light
    vec4 lDirection = viewMatrix * vec4( uDirLightPos, 0.0 );
    vec3 lVector = normalize( lDirection.xyz );

    //  N * L. Normal must be normalized, since it's interpolated.
    vec3 normal = normalize( vNormal );

    // check the diffuse dot product against uBorder and adjust
    // this diffuse value accordingly.
    float diffuse = max( dot( normal, lVector ), 0.0);

    if (diffuse > 0.95)
        color = vec4(1.0,0.0,0.0,1.0);
    else if (diffuse > 0.85)
        color = vec4(0.9,0.0,0.0,1.0);
    else if (diffuse > 0.75)
        color = vec4(0.8,0.0,0.0,1.0);
    else if (diffuse > 0.65)
        color = vec4(0.7,0.0,0.0,1.0);
    else if (diffuse > 0.55)
        color = vec4(0.6,0.0,0.0,1.0);
    else if (diffuse > 0.45)
        color = vec4(0.5,0.0,0.0,1.0);
    else if (diffuse > 0.35)
        color = vec4(0.4,0.0,0.0,1.0);
    else if (diffuse > 0.25)
        color = vec4(0.3,0.0,0.0,1.0);
    else if (diffuse > 0.15)
        color = vec4(0.2,0.0,0.0,1.0);
    else if (diffuse > 0.05)
        color = vec4(0.1,0.0,0.0,1.0);
    else
        color = vec4(0.05,0.0,0.0,1.0);

    gl_FragColor = color;

顶点着色器

    vec3 mod289(vec3 x)
{
    return x - floor(x * (1.0 / 289.0)) * 289.0;
}

vec4 mod289(vec4 x)
{
    return x - floor(x * (1.0 / 289.0)) * 289.0;
}

vec4 permute(vec4 x)
{
    return mod289(((x*34.0)+1.0)*x);
}

vec4 taylorInvSqrt(vec4 r)
{
    return 1.79284291400159 - 0.85373472095314 * r;
}

vec3 fade(vec3 t) {
    return t*t*t*(t*(t*6.0-15.0)+10.0);
}

// Classic Perlin noise
float cnoise(vec3 P)
{
    vec3 Pi0 = floor(P); // Integer part for indexing
    vec3 Pi1 = Pi0 + vec3(1.0); // Integer part + 1
    Pi0 = mod289(Pi0);
    Pi1 = mod289(Pi1);
    vec3 Pf0 = fract(P); // Fractional part for interpolation
    vec3 Pf1 = Pf0 - vec3(1.0); // Fractional part - 1.0
    vec4 ix = vec4(Pi0.x, Pi1.x, Pi0.x, Pi1.x);
    vec4 iy = vec4(Pi0.yy, Pi1.yy);
    vec4 iz0 = Pi0.zzzz;
    vec4 iz1 = Pi1.zzzz;

    vec4 ixy = permute(permute(ix) + iy);
    vec4 ixy0 = permute(ixy + iz0);
    vec4 ixy1 = permute(ixy + iz1);

    vec4 gx0 = ixy0 * (1.0 / 7.0);
    vec4 gy0 = fract(floor(gx0) * (1.0 / 7.0)) - 0.5;
    gx0 = fract(gx0);
    vec4 gz0 = vec4(0.5) - abs(gx0) - abs(gy0);
    vec4 sz0 = step(gz0, vec4(0.0));
    gx0 -= sz0 * (step(0.0, gx0) - 0.5);
    gy0 -= sz0 * (step(0.0, gy0) - 0.5);

    vec4 gx1 = ixy1 * (1.0 / 7.0);
    vec4 gy1 = fract(floor(gx1) * (1.0 / 7.0)) - 0.5;
    gx1 = fract(gx1);
    vec4 gz1 = vec4(0.5) - abs(gx1) - abs(gy1);
    vec4 sz1 = step(gz1, vec4(0.0));
    gx1 -= sz1 * (step(0.0, gx1) - 0.5);
    gy1 -= sz1 * (step(0.0, gy1) - 0.5);

    vec3 g000 = vec3(gx0.x,gy0.x,gz0.x);
    vec3 g100 = vec3(gx0.y,gy0.y,gz0.y);
    vec3 g010 = vec3(gx0.z,gy0.z,gz0.z);
    vec3 g110 = vec3(gx0.w,gy0.w,gz0.w);
    vec3 g001 = vec3(gx1.x,gy1.x,gz1.x);
    vec3 g101 = vec3(gx1.y,gy1.y,gz1.y);
    vec3 g011 = vec3(gx1.z,gy1.z,gz1.z);
    vec3 g111 = vec3(gx1.w,gy1.w,gz1.w);

    vec4 norm0 = taylorInvSqrt(vec4(dot(g000, g000), dot(g010, g010), dot(g100, g100), dot(g110, g110)));
    g000 *= norm0.x;
    g010 *= norm0.y;
    g100 *= norm0.z;
    g110 *= norm0.w;
    vec4 norm1 = taylorInvSqrt(vec4(dot(g001, g001), dot(g011, g011), dot(g101, g101), dot(g111, g111)));
    g001 *= norm1.x;
    g011 *= norm1.y;
    g101 *= norm1.z;
    g111 *= norm1.w;

    float n000 = dot(g000, Pf0);
    float n100 = dot(g100, vec3(Pf1.x, Pf0.yz));
    float n010 = dot(g010, vec3(Pf0.x, Pf1.y, Pf0.z));
    float n110 = dot(g110, vec3(Pf1.xy, Pf0.z));
    float n001 = dot(g001, vec3(Pf0.xy, Pf1.z));
    float n101 = dot(g101, vec3(Pf1.x, Pf0.y, Pf1.z));
    float n011 = dot(g011, vec3(Pf0.x, Pf1.yz));
    float n111 = dot(g111, Pf1);

    vec3 fade_xyz = fade(Pf0);
    vec4 n_z = mix(vec4(n000, n100, n010, n110), vec4(n001, n101, n011, n111), fade_xyz.z);
    vec2 n_yz = mix(n_z.xy, n_z.zw, fade_xyz.y);
    float n_xyz = mix(n_yz.x, n_yz.y, fade_xyz.x); 
    return 2.2 * n_xyz;
}

// Classic Perlin noise, periodic variant
float pnoise(vec3 P, vec3 rep)
{
    vec3 Pi0 = mod(floor(P), rep); // Integer part, modulo period
    vec3 Pi1 = mod(Pi0 + vec3(1.0), rep); // Integer part + 1, mod period
    Pi0 = mod289(Pi0);
    Pi1 = mod289(Pi1);
    vec3 Pf0 = fract(P); // Fractional part for interpolation
    vec3 Pf1 = Pf0 - vec3(1.0); // Fractional part - 1.0
    vec4 ix = vec4(Pi0.x, Pi1.x, Pi0.x, Pi1.x);
    vec4 iy = vec4(Pi0.yy, Pi1.yy);
    vec4 iz0 = Pi0.zzzz;
    vec4 iz1 = Pi1.zzzz;

    vec4 ixy = permute(permute(ix) + iy);
    vec4 ixy0 = permute(ixy + iz0);
    vec4 ixy1 = permute(ixy + iz1);

    vec4 gx0 = ixy0 * (1.0 / 7.0);
    vec4 gy0 = fract(floor(gx0) * (1.0 / 7.0)) - 0.5;
    gx0 = fract(gx0);
    vec4 gz0 = vec4(0.5) - abs(gx0) - abs(gy0);
    vec4 sz0 = step(gz0, vec4(0.0));
    gx0 -= sz0 * (step(0.0, gx0) - 0.5);
    gy0 -= sz0 * (step(0.0, gy0) - 0.5);

    vec4 gx1 = ixy1 * (1.0 / 7.0);
    vec4 gy1 = fract(floor(gx1) * (1.0 / 7.0)) - 0.5;
    gx1 = fract(gx1);
    vec4 gz1 = vec4(0.5) - abs(gx1) - abs(gy1);
    vec4 sz1 = step(gz1, vec4(0.0));
    gx1 -= sz1 * (step(0.0, gx1) - 0.5);
    gy1 -= sz1 * (step(0.0, gy1) - 0.5);

    vec3 g000 = vec3(gx0.x,gy0.x,gz0.x);
    vec3 g100 = vec3(gx0.y,gy0.y,gz0.y);
    vec3 g010 = vec3(gx0.z,gy0.z,gz0.z);
    vec3 g110 = vec3(gx0.w,gy0.w,gz0.w);
    vec3 g001 = vec3(gx1.x,gy1.x,gz1.x);
    vec3 g101 = vec3(gx1.y,gy1.y,gz1.y);
    vec3 g011 = vec3(gx1.z,gy1.z,gz1.z);
    vec3 g111 = vec3(gx1.w,gy1.w,gz1.w);

    vec4 norm0 = taylorInvSqrt(vec4(dot(g000, g000), dot(g010, g010), dot(g100, g100), dot(g110, g110)));
    g000 *= norm0.x;
    g010 *= norm0.y;
    g100 *= norm0.z;
    g110 *= norm0.w;
    vec4 norm1 = taylorInvSqrt(vec4(dot(g001, g001), dot(g011, g011), dot(g101, g101), dot(g111, g111)));
    g001 *= norm1.x;
    g011 *= norm1.y;
    g101 *= norm1.z;
    g111 *= norm1.w;

    float n000 = dot(g000, Pf0);
    float n100 = dot(g100, vec3(Pf1.x, Pf0.yz));
    float n010 = dot(g010, vec3(Pf0.x, Pf1.y, Pf0.z));
    float n110 = dot(g110, vec3(Pf1.xy, Pf0.z));
    float n001 = dot(g001, vec3(Pf0.xy, Pf1.z));
    float n101 = dot(g101, vec3(Pf1.x, Pf0.y, Pf1.z));
    float n011 = dot(g011, vec3(Pf0.x, Pf1.yz));
    float n111 = dot(g111, Pf1);

    vec3 fade_xyz = fade(Pf0);
    vec4 n_z = mix(vec4(n000, n100, n010, n110), vec4(n001, n101, n011, n111), fade_xyz.z);
    vec2 n_yz = mix(n_z.xy, n_z.zw, fade_xyz.y);
    float n_xyz = mix(n_yz.x, n_yz.y, fade_xyz.x); 
    return 2.2 * n_xyz;
}

varying vec2 vUv;
varying float noise;
uniform float time;

// for the cell shader
varying vec3 vNormal;
varying vec3 vViewPosition;

float turbulence( vec3 p ) {
    float w = 100.0;
    float t = -.5;
    for (float f = 1.0 ; f <= 10.0 ; f++ ){
        float power = pow( 2.0, f );
        t += abs( pnoise( vec3( power * p ), vec3( 10.0, 10.0, 10.0 ) ) / power );
    }
    return t;
}

varying vec3 vertexWorldPos;

void main() {

    vUv = uv;

    // add time to the noise parameters so it's animated
    noise = 10.0 *  -.10 * turbulence( .5 * normal + time );
    float b = 25.0 * pnoise( 0.05 * position + vec3( 2.0 * time ), vec3( 100.0 ) );
    float displacement = - 10. - noise + b;

    vec3 newPosition = position + normal * displacement;
    gl_Position = projectionMatrix * modelViewMatrix * vec4( newPosition, 1.0 );

    // for the cell shader effect
    vNormal = normalize( normalMatrix * normal );
    vec4 mvPosition = modelViewMatrix * vec4( position, 1.0 );
    vViewPosition = -mvPosition.xyz;
}

值得一提

我正在使用 Three.js 库
我的光源是 THREE.SpotLight 的一个实例

Answer 1

首先，阴影是完全不同的。您的问题是置换后每个顶点的法线没有变化。纠正这一点不会让你产生阴影，但你的光照至少会在你置换的几何体上有所不同。

如果您可以访问偏导数，则可以在片段着色器中执行此操作。否则，由于缺乏顶点邻接信息，您在 GL ES 中有点不走运。您还可以使用几何着色器计算每个面的法线，但这在 WebGL 中不是一个选项。

这应该是实现这一点所需的所有更改，请注意，它需要偏导数支持(OpenGL ES 2.0 中的可选扩展)。

顶点着色器:

varying vec3 vertexViewPos; // NEW

void main() {
  ...

  vec3 newPosition = position + normal * displacement;
  vertexViewPos    = (modelViewMatrix * vec4 (newPosition, 1.0)).xyz; // NEW

  ...
}

片段着色器:

#extension GL_OES_standard_derivatives : require

uniform vec3 uMaterialColor;
uniform vec3 uDirLightPos;
uniform vec3 uDirLightColor;
uniform float uKd;
uniform float uBorder;
varying vec3 vNormal;
varying vec3 vViewPosition;

varying vec3 vertexViewPos; // NEW

void main() {
    vec4 color;

    // compute direction to light
    vec4 lDirection = viewMatrix * vec4( uDirLightPos, 0.0 );
    vec3 lVector = normalize( lDirection.xyz );

    //  N * L. Normal must be normalized, since it's interpolated.
    vec3 normal = normalize(cross (dFdx (vertexViewPos), dFdy (vertexViewPos))); // UPDATED

    ...
 }

要在 WebGL 中启用偏导数支持，您需要像这样检查扩展:

var ext = gl.getExtension("OES_standard_derivatives");
if (!ext) {
    alert("OES_standard_derivatives does not exist on this machine");
    return;
}

// proceed with the shaders above.