shader 的复习

Vertex Shader：

// vertex shader
uniform vec3 lightpos; //传入光源的模型坐标吧
uniform vec4 eyepos;
 
varying vec3 lightdir;
varying vec3 halfvec;
varying vec3 norm;
varying vec3 eyedir;
 
attribute vec3 rm_Tangent;
 
void main(void)
{
   vec4 pos = gl_ModelViewMatrix * gl_Vertex;
   pos = pos / pos.w;
   
//把光源和眼睛从模型空间转换到视图空间
   vec4 vlightPos = (gl_ModelViewMatrix * vec4(lightpos, 1.0));
   vec4 veyePos   = (gl_ModelViewMatrix * eyepos);
   
   lightdir = normalize(vlightPos.xyz - pos.xyz);
   vec3 eyedir = normalize(veyePos.xyz - pos.xyz);
   
  //模型空间下的TBN
   norm = normalize(gl_NormalMatrix * gl_Normal);
 
   vec3 vtangent  = normalize(gl_NormalMatrix * rm_Tangent);
 
   vec3 vbinormal = cross(norm,vtangent);
   
   //将光源向量和视线向量转换到TBN切线空间
   lightdir.x = dot(vtangent,  lightdir);
   lightdir.y = dot(vbinormal, lightdir); 
   lightdir.z = dot(norm     , lightdir);
   lightdir = normalize(lightdir);
   
   eyedir.x = dot(vtangent,  eyedir);
   eyedir.y = dot(vbinormal, eyedir);
   eyedir.z = dot(norm     , eyedir);
   eyedir = normalize(eyedir);
   
   halfvec = normalize(lightdir + eyedir);
 
   gl_FrontColor = gl_Color;
   
   gl_TexCoord[0] = gl_MultiTexCoord0;
   
   gl_Position = ftransform();
}

fragment shader：

 
//fragment shader
uniform float shiness;
uniform vec4 ambient, diffuse, specular;
 
uniform sampler2D bumptex;
uniform sampler2D basetex;
 
float amb = 0.2;
float diff = 0.2;
float spec = 0.6;
 
varying vec3 lightdir;
varying vec3 halfvec;
varying vec3 norm;
varying vec3 eyedir;
 
void main(void)
{
   vec3 vlightdir = normalize(lightdir);
   vec3 veyedir = normalize(eyedir);
 
   vec3 vnorm =   normalize(norm);
   vec3 vhalfvec =  normalize(halfvec);  
   
   vec4 baseCol = texture2D(basetex, gl_TexCoord[0].xy); 
   
   //Normal Map里的像素normal定义于该像素的切线空间
   vec3 tbnnorm = texture2D(bumptex, gl_TexCoord[0].xy).xyz;
   
   tbnnorm = normalize((tbnnorm  - vec3(0.5))* 2.0); 
   
   float diffusefract =  max( dot(lightdir,tbnnorm) , 0.0); 
   float specularfract = max( dot(vhalfvec,tbnnorm) , 0.0);
   
   if(specularfract > 0.0){
   specularfract = pow(specularfract, shiness);
   }
   
   gl_FragColor = vec4(amb * ambient.xyz * baseCol.xyz
                 + diff * diffuse.xyz * diffusefract * baseCol.xyz
                 + spec * specular.xyz * specularfract ,1.0);
}