简单的光照模型

看了康玉之大牛的《GPU 编程与CG 语言之阳春白雪下里巴人》，和放风筝的程序员的博客，自己也来写写光照模型

1. Lambert光照模型，也就是漫反射光照模型。它考虑的是ambient光和diffuse光对物体的综合影响

struct VertexIn 
{ 
  float4 position : POSITION;        
  float4 normal   : NORMAL; 
}; 
struct VertexScreen 
{ 
   float4 oPosition : POSITION; 
   float4 color     : COLOR; 
}; 

void main_v(VertexIn posIn, 
            out VertexScreen posOut, 
 
            uniform float3 globalAmbient, 
            uniform float3 lightPosition, 
            uniform float3 lightColor, 
            uniform float3 Kd) 
{ 
    // Get OpenGL state matrices
    float4x4 modelViewProj = glstate.matrix.mvp;
    float4x4 worldMatrix = glstate.matrix.modelview[0];
    float4x4 worldMatrix_IT = glstate.matrix.invtrans.modelview[0];
  
  
    posOut.oPosition = mul(modelViewProj, posIn.position); 
 
    float3 worldPos = mul(worldMatrix, posIn.position).xyz; 
    float3 N = mul(worldMatrix_IT, posIn.normal).xyz; 
    N = normalize(N); 
     
    //计算入射光方向 
    float3 L = lightPosition - worldPos; 
    L = normalize(L); 
     
    //计算方向光漫反射光强 
    float3 diffuseColor = Kd*lightColor*max(dot(N, L), 0); 
     
    //计算环境光漫反射光强 
    float3 ambientColor = Kd*globalAmbient; 
     
    posOut.color.xyz = diffuseColor+ambientColor; 
    posOut.color.w = 1; 
} 

#include <stdio.h>
#include <gl/glut.h>
#include <cg/cg.h>
#include <cg/cgGL.h>
#pragma comment(lib,"cg.lib")
#pragma comment(lib,"cgGL.lib")

#define WINDOW_SIZE 800

static CGcontext Context = NULL;
static CGprogram VertexProgram = NULL;
static CGprofile VertexProfile;
static CGparameter globalAmbient = NULL;
static CGparameter lightPosition = NULL;
static CGparameter lightColor = NULL;
static CGparameter Kd = NULL;



void init()
{
    glShadeModel(GL_SMOOTH);
    glClearColor(0.0f,0.0f,0.0f,0.0f);
    glClearDepth(1.0f);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);
    glHint(GL_PERSPECTIVE_CORRECTION_HINT,GL_NICEST);

    //-------------------------------cg init-------------------------------------------------------
    Context = cgCreateContext();
    VertexProfile = cgGLGetLatestProfile(CG_GL_VERTEX);
    VertexProgram = cgCreateProgramFromFile(Context,CG_SOURCE, "lightmodle.cg",VertexProfile,"main_v", NULL);
    cgGLLoadProgram(VertexProgram);
    globalAmbient = cgGetNamedParameter(VertexProgram, "globalAmbient");
    lightPosition = cgGetNamedParameter(VertexProgram, "lightPosition");
    lightColor = cgGetNamedParameter(VertexProgram, "lightColor");
    Kd = cgGetNamedParameter(VertexProgram, "Kd");
}

void display()
{
    cgGLBindProgram(VertexProgram);
    cgGLSetParameter3f(globalAmbient, 0.2, 0.2, 0.2);//环境光暗灰色
    cgGLSetParameter3f(lightPosition, 0.0, 0.0, 1.0);//光源放在正前面
    cgGLSetParameter3f(lightColor, 1.0, 1.0, 1.0);//明亮的白色的点光源
    cgGLSetParameter3f(Kd, 0.8, 0.8, 0.8);//材料对光的反射属性
    cgGLEnableProfile(VertexProfile);

    static float rotate=0.0;
    rotate+=0.1;

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();

    glTranslatef(0.0,0.0,-6.0);
    glRotatef(30,1.0,0.0,0.0);
    glRotatef(rotate,0.0,1.0,0.0);
    glutSolidTeapot(1.0);
    cgGLDisableProfile(VertexProfile);

    glutSwapBuffers();
}

void reshape(int w,int h)
{
    if (h==0) h=1;
    glViewport(0,0,w,h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45.0f,(GLfloat)w/(GLfloat)h,0.01f,400.0f);
    glMatrixMode(GL_MODELVIEW);
}

int main(int argc,char* argv[])
{
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGBA);
    glutCreateWindow(argv[0]);
    glutReshapeWindow(WINDOW_SIZE,WINDOW_SIZE);

    glutDisplayFunc(display);
    glutIdleFunc(display);
    glutReshapeFunc(reshape);

    init();
    glutMainLoop();
    cgDestroyProgram(VertexProgram);
    cgDestroyContext(Context);
    return 0;
}

效果图：

2. Phong光照模型，这个模型计算了镜面高光(Specular)：

struct VertexIn 
{ 
  float4 position  : POSITION;        
  float4 normal   : NORMAL; 
}; 
 
struct VertexScreen 
{ 
   float4 oPosition      : POSITION; 
   float4 objectPos      : TEXCOORD0; 
   float4 objectNormal   : TEXCOORD1; 
}; 

void main_v( VertexIn posIn, 
             out VertexScreen posOut) 
{
    float4x4 modelViewProj = glstate.matrix.mvp;
     
    posOut.oPosition = mul(modelViewProj, posIn.position); 
    posOut.objectPos = posIn.position; 
    posOut.objectNormal = posIn.normal; 
}


void main_f( VertexScreen posIn, 
             out float4 color     : COLOR, 
 
              uniform float3 globalAmbient, 
              uniform float3 eyePosition, 
              uniform float3 lightPosition, 
              uniform float3 lightColor,             
              uniform float3 Kd, 
              uniform float3 Ks, 
              uniform float  shininess) 
{
    float4x4 worldMatrix = glstate.matrix.modelview[0];
    float4x4 worldMatrix_IT = glstate.matrix.invtrans.modelview[0];
     
    float3 worldPos = mul(worldMatrix, posIn.objectPos).xyz; 
    float3 N = mul(worldMatrix_IT, posIn.objectNormal).xyz; 
    N = normalize(N); 
   
    //计算入射光方向、视线方向、反射光线方向 
    float3 L = normalize(lightPosition - worldPos); 
    float3 V = normalize(eyePosition - worldPos); 
    float3 R = 2*max(dot(N, L), 0)*N-L; 
    R = normalize(R); 
 
    //计算漫反射分量 
    float3 diffuseColor = Kd * globalAmbient+Kd*lightColor*max(dot(N, L), 0); 
   
    //计算镜面反射分量 
    float3 specularColor = Ks * lightColor*pow(max(dot(V, R), 0), shininess); 
   
    color.xyz = diffuseColor + specularColor; 
    color.w = 1; 
}

#include <stdio.h>
#include <gl/glut.h>
#include <cg/cg.h>
#include <cg/cgGL.h>
#pragma comment(lib,"cg.lib")
#pragma comment(lib,"cgGL.lib")

#define WINDOW_SIZE 800

static CGcontext Context = NULL;
static CGprogram VertexProgram = NULL;
static CGprogram FragementProgram = NULL;
static CGprofile VertexProfile;
static CGprofile FragementProfile;

static CGparameter globalAmbient = NULL;
static CGparameter eyePosition = NULL;
static CGparameter lightPosition = NULL;
static CGparameter lightColor = NULL;
static CGparameter Kd = NULL;
static CGparameter Ks = NULL;
static CGparameter shininess = NULL;


void init()
{
    glShadeModel(GL_SMOOTH);
    glClearColor(0.0f,0.0f,0.0f,0.0f);
    glClearDepth(1.0f);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);
    glHint(GL_PERSPECTIVE_CORRECTION_HINT,GL_NICEST);

    //-------------------------------cg init-------------------------------------------------------
    Context = cgCreateContext();
    //顶点程序
    VertexProfile = cgGLGetLatestProfile(CG_GL_VERTEX);
    VertexProgram = cgCreateProgramFromFile(Context,CG_SOURCE, "lightmodle.cg",VertexProfile,"main_v", NULL);
    cgGLLoadProgram(VertexProgram);
    //片段程序
    FragementProfile = cgGLGetLatestProfile(CG_GL_FRAGMENT);
    FragementProgram = cgCreateProgramFromFile(Context,CG_SOURCE, "lightmodle.cg",FragementProfile,"main_f", NULL);
    cgGLLoadProgram(FragementProgram);

    globalAmbient = cgGetNamedParameter(FragementProgram, "globalAmbient");
    eyePosition = cgGetNamedParameter(FragementProgram, "eyePosition");
    lightPosition = cgGetNamedParameter(FragementProgram, "lightPosition");
    lightColor = cgGetNamedParameter(FragementProgram, "lightColor");
    Kd = cgGetNamedParameter(FragementProgram, "Kd");
    Ks = cgGetNamedParameter(FragementProgram, "Ks");
    shininess = cgGetNamedParameter(FragementProgram, "shininess");
}

void display()
{
    cgGLEnableProfile(VertexProfile);
    cgGLEnableProfile(FragementProfile);
    cgGLBindProgram(VertexProgram);
    cgGLBindProgram(FragementProgram);

    cgGLSetParameter3f(globalAmbient, 0.2, 0.2, 0.2);//环境光暗灰色
    cgGLSetParameter3f(eyePosition, 0.0, 0.0, 0.0);//视点位置
    cgGLSetParameter3f(lightPosition, 0.0, 0.0, 1.0);//光源放在正前面
    cgGLSetParameter3f(lightColor, 1.0, 1.0, 1.0);//明亮的白色的点光源
    cgGLSetParameter3f(Kd, 0.8, 0.8, 0.8);//材料对光的反射属性
    cgGLSetParameter3f(Ks, 1.0, 1.0, 1.0);//材质的镜面反射系数
    cgGLSetParameter1f(shininess, 20);//高光指数
    cgGLEnableProfile(FragementProfile);

    static float rotate=0.0;
    rotate+=0.1;

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();

    glTranslatef(0.0,0.0,-6.0);
    glRotatef(30,1.0,0.0,0.0);
    glRotatef(rotate,0.0,1.0,0.0);
    glutSolidTeapot(1.0);
    cgGLDisableProfile(VertexProfile);
    cgGLDisableProfile(FragementProfile);

    glutSwapBuffers();
}

void reshape(int w,int h)
{
    if (h==0) h=1;
    glViewport(0,0,w,h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45.0f,(GLfloat)w/(GLfloat)h,0.01f,400.0f);
    glMatrixMode(GL_MODELVIEW);
}

int main(int argc,char* argv[])
{
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGBA);
    glutCreateWindow(argv[0]);
    glutReshapeWindow(WINDOW_SIZE,WINDOW_SIZE);

    glutDisplayFunc(display);
    glutIdleFunc(display);
    glutReshapeFunc(reshape);

    init();
    glutMainLoop();
    cgDestroyProgram(VertexProgram);
    cgDestroyProgram(FragementProgram);
    cgDestroyContext(Context);
    return 0;
}

效果图：