glsl 1.3+中的点光源/聚光灯衰减？

Question

我一直在使用OpenGL的Superbible（第5版）点光源示例。

我发现它们缺少集成到旧照明模型中的恒定，线性和二次衰减值，所以我写了一个基于此ogre guide的衰减值的点光源着色器。

结果已经完全离奇了。 如何才能在新的glsl上获得合理的光线衰减？是否有衰减常量的glsl表格？

照片管理

衰减在距离99 -sphere是黑色的，光在距离蓝光

衰减50 -sphere是黑的，光被蓝光

衰减在距离16 -sphere是黑的，光被发射蓝色

衰减在距离2 -sphere是黑的，光被发射蓝色

样品顶点和片段程序：

顶点程序：

//point light per pixel vertex program 
#version 130 

// Incoming per vertex... position and normal 
in vec4 vVertex; 
in vec3 vNormal; 


uniform mat4 mvpMatrix; 
uniform mat4 mvMatrix; 
uniform mat3 normalMatrix; 
uniform vec3 vLightPosition; 

// Color to fragment program 
smooth out vec3 vVaryingNormal; 
smooth out vec3 vVaryingLightDir; 

out float dist; 
out float constantAttenuation; 
out float linearAttenuation; 
out float quadraticAttenuation; 

void main(void) 
    { 
    // Get surface normal in eye coordinates 
    vVaryingNormal = normalMatrix * vNormal; 

    // Get vertex position in eye coordinates 
    vec4 vPosition4 = mvMatrix * vVertex; 
    vec3 vPosition3 = vPosition4.xyz/vPosition4.w; 

    //get distance to light source 
    dist=length(vLightPosition-vPosition3); 

    //write proper attenuation values 

    if (dist<7.0){ 
     constantAttenuation=1.0; 
     linearAttenuation=0.7; 
     quadraticAttenuation=1.8; 
    } 

    else if (dist<13.0){ 
     constantAttenuation=1.0; 
     linearAttenuation=0.35; 
     quadraticAttenuation=0.44; 
    } 

    else if (dist<20.0){ 
     constantAttenuation=1.0; 
     linearAttenuation=0.22; 
     quadraticAttenuation=0.20; 
    } 

    if (dist<32.0){ 
     constantAttenuation=1.0; 
     linearAttenuation=0.14; 
     quadraticAttenuation=0.07; 
    } 
    if (dist<50.0){ 
     constantAttenuation=1.0; 
     linearAttenuation=0.09; 
     quadraticAttenuation=0.32; 
    } 

    if (dist<65.0){ 
     constantAttenuation=1.0; 
     linearAttenuation=0.07; 
     quadraticAttenuation=0.017; 
    } 

    if (dist<100.0){ 
     constantAttenuation=1.0; 
     linearAttenuation=0.045; 
     quadraticAttenuation=0.0075; 
    } 



    // Get vector to light source 
    vVaryingLightDir = normalize(vLightPosition - vPosition3); 

    // Don't forget to transform the geometry! 
    gl_Position = mvpMatrix * vVertex; 
    } 

片断程序：

//point light per pixel fragment program 

#version 130 

out vec4 vFragColor; 

uniform vec4 ambientColor; 
uniform vec4 diffuseColor; 
uniform vec4 specularColor; 

smooth in vec3 vVaryingNormal; 
smooth in vec3 vVaryingLightDir; 

in float dist; 
in float constantAttenuation; 
in float linearAttenuation; 
in float quadraticAttenuation; 

void main(void){ 

    float att; 

    att = 1.0/constantAttenuation + linearAttenuation*dist +quadraticAttenuation*dist*dist; 

    // Dot product gives us diffuse intensity 
    float diff = max(0.0, dot(normalize(vVaryingNormal), normalize(vVaryingLightDir))); 

    // Multiply intensity by diffuse color, force alpha to 1.0 
    vFragColor = att*(diff * diffuseColor +ambientColor); // attenuation affects the diffuse component 

    // Specular Light 
    vec3 vReflection = normalize(reflect(-normalize(vVaryingLightDir), normalize(vVaryingNormal))); 

    float spec = max(0.0, dot(normalize(vVaryingNormal), vReflection)); 
    if(diff != 0) { 
     float fSpec = pow(spec, 128.0); 
     vFragColor.rgb += (att*vec3 (fSpec, fSpec, fSpec)); // attenuation affects the specular component 
     } 
    } 

Answer 1

最后我用眼前这个衰减值，该事情的作品可以接受：

 constantAttenuation=1.0; 
     linearAttenuation=0.22; 
     quadraticAttenuation=0.20; 

有一对夫妇括号失踪衰减师太的。

Answer 2

你的衰减公式是完全不正确的：

att = 1.0/constantAttenuation + linearAttenuation*dist +quadraticAttenuation*dist*dist; 

应改为：

att = constantAttenuation/((1+linearAttenuation*dist)*(1+quadraticAttenuation*dist*dist)). 

这就是为什么你所得到的球更轻的距离增加时。尝试适当的公式并发布结果。