OpenGL_砖块着色案例

- 日理万妓 2022-08-07 17:38 179阅读 0赞

效果图：

![20150421173835079][]

顶点着色器：

uniform vec3 LightPosition;
    
    const float SpecularContribution=0.3;
    const float DiffuseContribution=1.0-SpecularContribution;
    
    varying float LightIntensity;
    varying vec2 MCposition;
    
    void main(void)
    {
       vec3 ecPosition=vec3(gl_ModelViewMatrix*gl_Vertex);
       vec3 tnorm=normalize(gl_NormalMatrix*gl_Normal);
       vec3 lightVec=normalize(LightPosition-ecPosition);
       vec3 reflectVec=reflect(-lightVec,tnorm);
       vec3 viewVec=normalize(-ecPosition);
       float diffuse=max(dot(lightVec,tnorm),0.0);
       float spec=0.0;
       if(diffuse>0.0){
       spec=max(dot(reflectVec,viewVec),0.0);
       spec=pow(spec,16.0);
       }
       LightIntensity=DiffuseContribution*diffuse+SpecularContribution*spec;
       MCposition=gl_Vertex.xy;
       gl_Position = ftransform();
    }

片元着色器：

varying vec2 MCposition;
    varying float LightIntensity;
    
    void main(void)
    {
       vec3 BrickColor=vec3(0.7,0.3,0.2);
       vec3 MortarColor=vec3(0.85,0.86,0.84);
       vec2  BrickSize=vec2(0.1,0.05638);
       vec2  BrickPct=vec2(0.9,0.85);
       vec3 color;
       vec2 position,useBrick;
       position=MCposition/BrickSize;
       if(fract(position.y*0.5)>0.5) position.x+=0.5;
       position=fract(position);
       useBrick=step(position,BrickPct);
       
       color=mix(MortarColor,BrickColor,useBrick.x*useBrick.y);
       color*=LightIntensity;   
       
       gl_FragColor = vec4( color, 1.0 );
    }

执行代码：

<pre name="code" class="cpp">#include <stdio.h>
    #include <stdlib.h>
    #include "stdafx.h"
    #include <math.h>
    #ifdef _WIN32
    	#include <windows.h>
    	#include <wingdi.h>
    	#define GLUT_DISABLE_ATEXIT_HACK
    #endif /* _WIN32 */
    
    #include "glew.h"
    
    #ifndef M_PI
    #define M_PI 3.14159265358979323846
    #endif
    
    extern void shaderAttachFromFile(GLuint,GLenum,const char *);//加载shader方法，请参考我的博客，有相关介绍
    
    static GLuint g_program;
    static GLuint g_programCameraPositionLocation;
    static GLuint g_programLightPositionLocation;
    static GLuint g_programLightColorLocation;
    
    static GLuint g_cylinderBufferId;
    static unsigned int g_cylinderNumVertices;
    
    static float g_cameraPosition[3];
    
    #define NUM_LIGHTS 1
    static float g_lightPosition[NUM_LIGHTS*3];

//创建圆柱
    static void createCylinder(unsigned int divisions)
    {
    	const int floatsPerVertex=6;
    	unsigned int i,size;
    	float *v;
    
    	g_cylinderNumVertices=(divisions+1)*2;
    	size=floatsPerVertex*g_cylinderNumVertices;
    
    	v=(float *)malloc(sizeof(float)*size);
    	for(i=0;i<=divisions;i++)
    	{
    		float r=((M_PI*2.0f)/(float)divisions)*(float)i;
    		unsigned int index1=i*2*floatsPerVertex;
    		unsigned int index2=index1+floatsPerVertex;
    
    		/* vertex positions */
    		v[index1 + 0] = cosf(r);
    		v[index1 + 1] = 1.0f;
    		v[index1 + 2] = -sinf(r);
    		v[index2 + 0] = cosf(r);
    		v[index2 + 1] = -1.0f;
    		v[index2 + 2] = -sinf(r);
    
    		/* normals */
    		v[index1 + 3] = cosf(r);
    		v[index1 + 4] = 0.0f;
    		v[index1 + 5] = -sinf(r);
    		v[index2 + 3] = v[index1 + 3];
    		v[index2 + 4] = v[index1 + 4];
    		v[index2 + 5] = v[index1 + 5];
    	}
    	glGenBuffers(1,&g_cylinderBufferId);
    	glBindBuffer(GL_ARRAY_BUFFER,g_cylinderBufferId);
    	glBufferData(GL_ARRAY_BUFFER,sizeof(float)*size,v,GL_STATIC_DRAW);
    	free(v);
    
    	glEnableClientState(GL_VERTEX_ARRAY);
    	glEnableClientState(GL_NORMAL_ARRAY);
    
    	glVertexPointer(3,GL_FLOAT,sizeof(float)*floatsPerVertex,0);
    	glNormalPointer(GL_FLOAT,sizeof(float)*floatsPerVertex,(const GLvoid *)(sizeof(float)*3));
    }
    //初始场景
    void sceneInit(void)
    {
    	GLint result;
    
    	g_program=glCreateProgram();
    	shaderAttachFromFile(g_program,GL_VERTEX_SHADER,"brick_v.glsl");
    	shaderAttachFromFile(g_program,GL_FRAGMENT_SHADER,"brick_f.glsl");
    	glLinkProgram(g_program);
    	glGetProgramiv(g_program,GL_LINK_STATUS,&result);
    	if(result==GL_FALSE)
    	{
    		GLint length;
    		char *log;
    		glGetProgramiv(g_program,GL_INFO_LOG_LENGTH,&length);
    		log=(char *)malloc(length);
    		glGetProgramInfoLog(g_program,length,&result,log);
    		fprintf(stderr,"sceneInit(): Program linking failed: %s\n",log);
    		free(log);
    		glDeleteProgram(g_program);
    		g_program=0;
    	}
    	/* get uniform locations */
    	
    	g_programLightPositionLocation = glGetUniformLocation(g_program, "LightPosition");
    	
    	/* create cylinder */
    	createCylinder(36);
    
    	g_lightPosition[0]=-10.0f;
    	g_lightPosition[1]=0.0f;
    	g_lightPosition[2]=4.0f;
    
    	
    	glLoadIdentity();
    	glTranslatef(0, 0, -4.0f);
    }
    //渲染场景
    void sceneRender(void)
    {
    	int i;
    
    	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
    	/* enable program and set uniform variables */
    	glUseProgram(g_program);
    	glUniform3fv(g_programLightPositionLocation, NUM_LIGHTS, g_lightPosition);
    
    	/* render the cylinder */
    	glDrawArrays(GL_TRIANGLE_STRIP, 0, g_cylinderNumVertices);
    
    	/* disable program */
    	glUseProgram(0);	
    }

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[20150421173835079]: /images/20220805/21b56b659eec4251905ad540513c8e7d.png