使用GLSL实现更多数量的局部光照

向右看齐 2022-08-05 15:07 122阅读 0赞

原文 [http://www.cnblogs.com/CGDeveloper/archive/2008/07/02/1233816.html][http_www.cnblogs.com_CGDeveloper_archive_2008_07_02_1233816.html]

众所周知，OpenGL固定管线只提供了最多8盏灯光。如何使得自己的场景之中拥有更多的灯光效果呢？  
这里提供一种使用GLSL shader实现更多数量的局部光照。  
  
在GLSL里，首先建立光照参数数据结构：

![None.gif][] struct  myLightParams  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][] ![dot.gif][] \{  
![InBlock.gif][]    bool enabled;  
![InBlock.gif][]    vec4 position;  
![InBlock.gif][]    vec4 ambient;  
![InBlock.gif][]    vec4 diffuse;  
![InBlock.gif][]    vec4 specular;  
![InBlock.gif][]    vec3 spotDirection;  
![InBlock.gif][]    float spotCutoff;  
![InBlock.gif][]    float spotExponent;  
![InBlock.gif][]    float constantAttenuation;  
![InBlock.gif][]    float linearAttenuation;  
![InBlock.gif][]    float quadraticAttenuation;  
![ExpandedBlockEnd.gif][]\} ;

然后，需要app传入的参数：

![None.gif][] const   int  maxLightCount  =   32 ;  
![None.gif][]uniform myLightParams light\[maxLightCount\];  
![None.gif][]uniform  bool  bLocalViewer;  
![None.gif][]uniform  bool  bSeperateSpecualr;

主函数：

![None.gif][] void  main()  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][] ![dot.gif][] \{  
![InBlock.gif][]    gl\_Position = gl\_ModelViewProjectionMatrix \* gl\_Vertex;  
![InBlock.gif][]    vec4 pos = gl\_ModelViewMatrix \* gl\_Vertex;  
![InBlock.gif][]    vec3 epos = vec3(pos)/pos.w;  
![InBlock.gif][]      
![InBlock.gif][]    vec3 normal = normalize(gl\_NormalMatrix \* gl\_Normal);  
![InBlock.gif][]      
![InBlock.gif][]    vec3 eye;  
![InBlock.gif][]    if (bLocalViewer)  
![InBlock.gif][]        eye = \-normalize(epos);  
![InBlock.gif][]    else  
![InBlock.gif][]        eye = vec3(0, 0, 1.0);  
![InBlock.gif][]      
![InBlock.gif][]    vec4 amb = vec4(0);  
![InBlock.gif][]    vec4 diff = vec4(0);  
![InBlock.gif][]    vec4 spec = vec4(0);  
![InBlock.gif][]      
![InBlock.gif][]    for (int i=0; i<maxLightCount; i\++)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    ![dot.gif][]\{  
![InBlock.gif][]        if (light\[i\].enabled == false)  
![InBlock.gif][]            continue;  
![InBlock.gif][]              
![InBlock.gif][]        if (light\[i\].position.w == 0)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            DirectionalLight(i, eye, epos, normal, amb, diff, spec);  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]        else if (light\[i\].spotCutoff == 180.0)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            PointLight(i, eye, epos, normal, amb, diff, spec);  
![ExpandedSubBlockEnd.gif][]        \}  
![InBlock.gif][]        else  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]        ![dot.gif][]\{  
![InBlock.gif][]            SpotLight(i, eye, epos, normal, amb, diff, spec);  
![ExpandedSubBlockEnd.gif][]        \}  
![ExpandedSubBlockEnd.gif][]    \}  
![InBlock.gif][]      
![InBlock.gif][]    vec4 color = gl\_FrontLightModelProduct.sceneColor \+   
![InBlock.gif][]                 amb \* gl\_FrontMaterial.ambient \+   
![InBlock.gif][]                 diff \* gl\_FrontMaterial.diffuse;  
![InBlock.gif][]                  
![InBlock.gif][]    if (bSeperateSpecualr)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    ![dot.gif][]\{  
![InBlock.gif][]        gl\_FrontSecondaryColor = spec \* gl\_FrontMaterial.specular;  
![ExpandedSubBlockEnd.gif][]    \}  
![InBlock.gif][]    else  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]    ![dot.gif][]\{  
![InBlock.gif][]        gl\_FrontSecondaryColor = vec4(0, 0, 0, 1.0);  
![InBlock.gif][]        color \+= spec \* gl\_FrontMaterial.specular;  
![ExpandedSubBlockEnd.gif][]    \}  
![InBlock.gif][]      
![InBlock.gif][]    gl\_FrontColor = color;  
![ExpandedBlockEnd.gif][]\}

对于方向光源的计算：

![None.gif][] void  DirectionalLight( int  i, vec3 eye, vec3 epos, vec3 normal,   
![None.gif][]                      inout vec4 amb, inout vec4 diff, inout vec4 spec)  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][] ![dot.gif][] \{  
![InBlock.gif][]    float dotVP = max(0, dot(normal, normalize(vec3(light\[i\].position))));  
![InBlock.gif][]    float dotHV = max(0, dot(normal, normalize(eye\+normalize(vec3(light\[i\].position)))));  
![InBlock.gif][]      
![InBlock.gif][]    amb \+= light\[i\].ambient;  
![InBlock.gif][]    diff \+= light\[i\].diffuse \* dotVP;  
![InBlock.gif][]    spec \+= light\[i\].specular \* pow(dotHV, gl\_FrontMaterial.shininess);  
![ExpandedBlockEnd.gif][]\}

对于点光源：

![None.gif][] void  PointLight( int  i, vec3 eye, vec3 epos, vec3 normal,   
![None.gif][]                inout vec4 amb, inout vec4 diff, inout vec4 spec)  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][] ![dot.gif][] \{  
![InBlock.gif][]    vec3 VP = vec3(light\[i\].position) \- epos;  
![InBlock.gif][]    float d = length(VP);  
![InBlock.gif][]    VP = normalize(VP);  
![InBlock.gif][]      
![InBlock.gif][]    float att = 1.0/(light\[i\].constantAttenuation \+ light\[i\].linearAttenuation\*d \+ light\[i\].quadraticAttenuation\*d\*d);  
![InBlock.gif][]    vec3 h = normalize(VP\+eye);  
![InBlock.gif][]      
![InBlock.gif][]    float dotVP = max(0, dot(normal, VP));  
![InBlock.gif][]    float dotHV = max(0, dot(normal, h));  
![InBlock.gif][]      
![InBlock.gif][]    amb \+= light\[i\].ambient \* att;  
![InBlock.gif][]    diff \+= light\[i\].diffuse \* dotVP \* att;  
![InBlock.gif][]    spec \+= light\[i\].specular \* pow(dotHV, gl\_FrontMaterial.shininess) \* att;  
![ExpandedBlockEnd.gif][]\}

对于聚光灯：

![None.gif][] void  SpotLight( int  i, vec3 eye, vec3 epos, vec3 normal,   
![None.gif][]               inout vec4 amb, inout vec4 diff, inout vec4 spec)  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][] ![dot.gif][] \{  
![InBlock.gif][]    vec3 VP = vec3(light\[i\].position) \- epos;  
![InBlock.gif][]    float d = length(VP);  
![InBlock.gif][]    VP = normalize(VP);  
![InBlock.gif][]      
![InBlock.gif][]    float att = 1.0/(light\[i\].constantAttenuation \+ light\[i\].linearAttenuation\*d \+ light\[i\].quadraticAttenuation\*d\*d);  
![InBlock.gif][]      
![InBlock.gif][]    float dotSpot = dot(\-VP, normalize(light\[i\].spotDirection));  
![InBlock.gif][]    float cosCutoff = cos(light\[i\].spotCutoff\*3.1415926/180.0);  
![InBlock.gif][]      
![InBlock.gif][]    float spotAtt = 0;  
![InBlock.gif][]    if (dotSpot < cosCutoff)  
![InBlock.gif][]        spotAtt = 0;  
![InBlock.gif][]    else  
![InBlock.gif][]        spotAtt = pow(dotSpot, light\[i\].spotExponent);   
![InBlock.gif][]      
![InBlock.gif][]    att \*= spotAtt;  
![InBlock.gif][]         
![InBlock.gif][]    vec3 h = normalize(VP\+eye);  
![InBlock.gif][]      
![InBlock.gif][]    float dotVP = max(0, dot(normal, VP));  
![InBlock.gif][]    float dotHV = max(0, dot(normal, h));  
![InBlock.gif][]      
![InBlock.gif][]    amb \+= light\[i\].ambient \* att;  
![InBlock.gif][]    diff \+= light\[i\].diffuse \* dotVP \* att;  
![InBlock.gif][]    spec \+= light\[i\].specular \* pow(dotHV, gl\_FrontMaterial.shininess) \* att;  
![ExpandedBlockEnd.gif][]\}

这样，对于场景之中的任意对象，它所能够接受计算的光源就可以突破8个的限制了。  
上述光照计算是遵循OpenGL spec的，因此与固定管线的效果是一致的。

[http_www.cnblogs.com_CGDeveloper_archive_2008_07_02_1233816.html]: http://www.cnblogs.com/CGDeveloper/archive/2008/07/02/1233816.html
[None.gif]: /images/20220805/c38a4ee8c85941a6bd7b0b62eaad03f0.png
[ExpandedBlockStart.gif]: http://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif
[ContractedBlock.gif]: http://www.cnblogs.com/Images/OutliningIndicators/ContractedBlock.gif
[dot.gif]: /images/20220805/188aa57385874ecda6fe028e63213c0d.png
[InBlock.gif]: /images/20220805/42e06955cd4145909cd85f9a89ae790a.png
[ExpandedBlockEnd.gif]: /images/20220805/89f599f3a38e4a698972854389020262.png
[ExpandedSubBlockStart.gif]: http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif
[ContractedSubBlock.gif]: http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif
[ExpandedSubBlockEnd.gif]: /images/20220805/1e314df6e1b74182b92edaa8e4d94a69.png