计算机图形学——OpenGL光照模型

野性酷女 2022-06-17 06:59 553阅读 0赞

# 计算机图形学——OpenGL光照模型 #

## 1、Phong光照模型 ##

![20170419220921791][] ![20170419221444877][]

镜面高光是由R、V决定， ks为材质的镜面反射系数， ns 是高光指数，V 表示从顶点到视点的观察方  
向， R 代表反射光方向。ns越大，反射光越集中；ns越小，表示物体越粗糙，反射光分散。

**实现实例**：

![20170420094322350][]

（源码在后面）

## 2、高洛德着色 ##

真实感图象颜色过渡均匀，图形显得非常光滑但是 镜面反射效果不太理想。

**实现实例：**

**![20170420093502924][]**

[（源码在这里）][Link 1]

## 3、二者的区别 ##

从图中可以看出，在光照强度相同时，Phong光照模型明暗交界处处理的很平滑。

![20170419223441231][]

Phong模型源码：

// 包含着色器加载库
    #include "shader.h"
    #include <GL/glut.h>
    GLfloat lightPosition[3] = { 30.0,30.0,-15.0 };
    GLfloat ambient[4] = { 0.0 , 0.0 , 0.0 , 1.0 };
    GLfloat lightcolor[4] = { 1.0 , 1.0 , 1.0 , 1.0 };
    GLfloat eyeposition[3] = { 0.0 , 10.0 , 30.0 };
    GLfloat Ns = 30;
    GLfloat attenuation = 0.01;
    GLuint programHandle;
    void mydisplay(){
    	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //清空颜色和深度缓冲
    	glEnable(GL_DEPTH_TEST);
        glShadeModel(GL_SMOOTH);//着色模型
    	programHandle = loadShaders("F:\\大三下课程\\Computer Graphic\\Shader\\gouraud.vert", "F:\\大三下课程\\Computer Graphic\\Shader\\gouraud.frag");
    	glUseProgram(programHandle);
    	glUniform3f(glGetUniformLocation(programHandle, "lightposition"), lightPosition[0], lightPosition[1], lightPosition[2]);
    	glUniform3f(glGetUniformLocation(programHandle, "eyeposition"), eyeposition[0], eyeposition[1], eyeposition[2]);
    	glUniform4f(glGetUniformLocation(programHandle, "ambient"), ambient[0], ambient[1], ambient[2], ambient[3]);
    	glUniform4f(glGetUniformLocation(programHandle, "lightcolor"), lightcolor[0], lightcolor[1], lightcolor[2], lightcolor[3]);
    	glUniform1f(glGetUniformLocation(programHandle, "Ns"), Ns);
    	glUniform1f(glGetUniformLocation(programHandle, "attenuation"), attenuation);
    	glutSolidTeapot(0.5);
    	glFlush();
    }
    int main(int argc, char *argv[])
    {
    	glewInit();
        glutInit(&argc, argv);
        glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
        glutInitWindowPosition(100, 100);
        glutInitWindowSize(600, 600);
        glutCreateWindow("ShaderLight");
    	glewInit(); 
        glutDisplayFunc(&mydisplay);
        glutMainLoop();
        return 0;
    }

顶点着色器：

uniform vec3 lightposition;//光源位置
    uniform vec3 eyeposition;//相机位置
    uniform vec4 ambient;//环境光颜色
    uniform vec4 lightcolor;//光源颜色
    uniform float Ns;//高光系数
    uniform float attenuation;//光线的衰减系数
    varying vec4 color;//向片段着色其传递的参数
    
    void main()
    {
    vec3 ECPosition = vec3(gl_ModelViewMatrix * gl_Vertex);
    vec3 N = normalize(gl_NormalMatrix * gl_Normal);
    vec3 L = normalize(lightposition - ECPosition);
    vec3 V = normalize(eyeposition - ECPosition);
    vec3 H = normalize(V + L);
    
    vec4 diffuse = lightcolor * max(dot(N , L) , 0);
    vec4 specular = lightcolor * pow(max(dot(N , H) , 0) , Ns) * attenuation;
    
    color = vec4(clamp((diffuse + specular) , 0.0 , 1.0));
    color = color + ambient;
    
    gl_Position = ftransform();
    }

片段着色器：

varying vec4 color;
    void main()
    {
    gl_FragColor = color;
    }

[20170419220921791]: https://img-blog.csdn.net/20170419220921791
[20170419221444877]: /images/20220617/58d66bc3140c47679fb4073ac635eff7.png
[20170420094322350]: /images/20220617/a8cde96e3179498e89c1e3c1f6d3cd0d.png
[20170420093502924]: /images/20220617/bfed3539df6243fd85709ca2c9d76519.png
[Link 1]: http://blog.csdn.net/qq_29721419/article/details/70161686
[20170419223441231]: /images/20220617/48196fcf76b3479696045a3879510dcb.png