GLSL实现Fresnel And Chromatic aberration

短命女 2022-08-07 05:42 109阅读 0赞

[http://blog.csdn.net/a3070173/archive/2008/11/13/3290091.aspx][http_blog.csdn.net_a3070173_archive_2008_11_13_3290091.aspx]

使用Shader实现菲涅尔和颜色色散效果很简单,在Cg教程和OpenGL Shader Language都有较  
为详细的介绍,个人觉得需要注意的地方是反射向量和折射向量应该在世界空间中进行计算,  
在模型空间和照相机空间中计算都会导致错误的结果.

具体着色器代码:  
顶点着色器:  
const float g\_fEta = 0.66; // 空气和玻璃的折射材质比例  
const float g\_fEtaR = 0.65;  
const float g\_fEtaG = 0.67;  
const float g\_fEtaB = 0.69;  
const float g\_fFresnelPower = 0.8;  
const float f = ((1.0-g\_fEta) \* (1.0-g\_fEta)) / ((1.0+g\_fEta) \* (1.0+g\_fEta));  
uniform vec3 g\_vec3CamerePositionInWorld;  
uniform int g\_iRenderMode;  
varying vec3  g\_vec3Reflect;  
varying vec3  g\_vec3Refract;  
varying vec3  g\_vec3Refract\_R;  
varying vec3  g\_vec3Refract\_G;  
varying vec3  g\_vec3Refract\_B;  
varying float g\_fFresnelRatio;  
void main()  
\{  
    vec3 NV = normalize(gl\_Vertex.xyz - g\_vec3CamerePositionInWorld);  
 vec3 N = gl\_Normal;  
   
 // 计算Fresnel比例  
    g\_fFresnelRatio = f + (1.0 - f) \* pow((1.0 - dot(-NV, N)), g\_fFresnelPower);  
 // 计算反射和折射光线  
 if (g\_iRenderMode == 0)  
 \{  
  g\_vec3Reflect = reflect(NV, N);  
  g\_vec3Reflect.y = -g\_vec3Reflect.y;  
 \}  
 else if (g\_iRenderMode == 1)  
 \{  
  g\_vec3Refract = refract(NV, N, g\_fEta);  
  g\_vec3Refract.y = -g\_vec3Refract.y;  
 \}  
 else if (g\_iRenderMode == 2)  
 \{  
  g\_vec3Reflect = reflect(NV, N);  
  g\_vec3Reflect.y = -g\_vec3Reflect.y;  
  g\_vec3Refract = refract(NV, N, g\_fEta);  
  g\_vec3Refract.y = -g\_vec3Refract.y;  
 \}  
 else  
 \{  
  g\_vec3Reflect = reflect(NV, N);  
  g\_vec3Reflect.y = -g\_vec3Reflect.y;  
  g\_vec3Refract\_R = refract(NV, N, g\_fEtaR);  
  g\_vec3Refract\_R.y = -g\_vec3Refract\_R.y;  
  g\_vec3Refract\_G = refract(NV, N, g\_fEtaG);  
  g\_vec3Refract\_G.y = -g\_vec3Refract\_G.y;  
  g\_vec3Refract\_B = refract(NV, N, g\_fEtaB);  
  g\_vec3Refract\_B.y = -g\_vec3Refract\_B.y;  
 \}  
    gl\_Position = ftransform();  
\}  
\}  
片元着色器:  
varying vec3  g\_vec3Reflect;  
varying vec3  g\_vec3Refract;  
varying vec3  g\_vec3Refract\_R;  
varying vec3  g\_vec3Refract\_G;  
varying vec3  g\_vec3Refract\_B;  
varying float g\_fFresnelRatio;  
uniform samplerCube g\_Cubemap;  
uniform int g\_iRenderMode;  
void main()  
\{  
 vec3 vec3FinalColor = vec3(0.0);  
   
 if (g\_iRenderMode == 0)  
 \{  
  vec3FinalColor = vec3(textureCube(g\_Cubemap, g\_vec3Reflect));  
 \}  
 else if (g\_iRenderMode == 1)  
 \{  
  vec3FinalColor = vec3(textureCube(g\_Cubemap, g\_vec3Refract));  
 \}  
 else if (g\_iRenderMode == 2)  
 \{  
  vec3 vec3ReflectColor = vec3(textureCube(g\_Cubemap, g\_vec3Reflect));  
  vec3 vec3RefractColor = vec3(textureCube(g\_Cubemap, g\_vec3Refract));  
  vec3FinalColor = mix(vec3RefractColor, vec3ReflectColor, g\_fFresnelRatio);  
 \}  
 else  
 \{  
  vec3 vec3ReflectColor = vec3(textureCube(g\_Cubemap, g\_vec3Reflect));  
  vec3 vec3RefractColor = vec3(0.0);  
  vec3RefractColor.r = vec3(textureCube(g\_Cubemap, g\_vec3Refract\_R)).r;  
  vec3RefractColor.g = vec3(textureCube(g\_Cubemap, g\_vec3Refract\_G)).g;  
  vec3RefractColor.b = vec3(textureCube(g\_Cubemap, g\_vec3Refract\_B)).b;  
  vec3FinalColor = mix(vec3RefractColor, vec3ReflectColor, g\_fFresnelRatio);  
 \}  
   
    gl\_FragColor = vec4(vec3FinalColor, 1.0);  
\}

Demo效果图:

![1.jpg][]

exe文件:http://www.fileupyours.com/view/219112/GLSL/Fresnel%20And%20Chromatic%20aberration%20Demo.rar

本文来自CSDN博客，转载请标明出处：[http://blog.csdn.net/a3070173/archive/2008/11/13/3290091.aspx][http_blog.csdn.net_a3070173_archive_2008_11_13_3290091.aspx]

[http_blog.csdn.net_a3070173_archive_2008_11_13_3290091.aspx]: http://blog.csdn.net/a3070173/archive/2008/11/13/3290091.aspx
[1.jpg]: /images/20220805/5f043a9fd48d470c8f59befb5e7880e4.png