Perlin噪音的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，我为我的“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.

我想要实现的是对我的顶点着色器生成的波形的阶梯着色（Toon着色，单元格着色......）效果，但片段着色器似乎将波浪看作是它们仍然是平面并且整个网格绘制为一种纯色。

我在这里缺少什么？球体完美地工作，但是平坦的表面都是均匀的阴影。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独立着色，但整个面部都是纯色。

场景

这就是我设置测试场景的方法。我有两个使用相同材质的网格 - 球体，平面和光源。

问题

正如您所见，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（perlin noise）在平面上工作得很漂亮。

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水平的光线，从而创建了这个...

旋转平面以面向光源将改变材质的颜色，但颜色再次均匀地施加在平面的整个表面上。

片段着色器

在所有的剧本中，小孩的荣耀大声笑。

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，阴影完全不同。这里你的问题是位移后每顶点法线没有变化。纠正这种情况不会让你产生阴影，但你的光照至少会因你移动的几何体而变化。

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，由于缺少顶点邻接信息，您在GL ES中运气不佳。您还可以使用几何着色器计算每面法线，但这不是WebGL中的选项。

这应该是实现此目的的所有必要更改，请注意它需要部分派生支持（ 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

  ...
}

Fragment Shader：

#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，您需要检查扩展名，如下所示：

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.