纹理贴图

8.5为面片添加纹理

Code：

glBegin(GL_QUADS);

  glTexCoord2f(0.0,0.0);glVertex3f(1.0,2.5,1.5);

  glTexCoord2f(0.0,0.6);glVertex3f(1.0,3.7,1.5);

  glTexCoord2f(0.8,0.6);glVertex3f(2.0,3.7,1.5);

  glTexCoord2f(0.8,0.0);glVertex3f(2.0,2..5,1.5);

glEnd();

注意：纹理坐标值不能超过1.0，否则按裁剪算法进行裁剪

 

为网格模型添加纹理坐标

1．纹理坐标列表

2．模型中纹理信息的组织方法

（1）面片顶点的数量

     面片法向的索引

     顶点索引的列表

     纹理坐标索引的列表

（2）面片顶点的数量

     顶点索引的列表

 

渲染纹理

理性线性绘制 rational linear rendering

双曲线插值   hyperbolic interpolation

视锥         view volume

 

纹理的卷绕和剪裁

卷绕 glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_REPEAT);

设置t方向上 将GL_TEXTURE_WRAP_T

关掉平铺 将GL_REPEAT替换为GL_CLAMP

 

纹理调和

创建一个发光体 可见亮度等于纹理值

glTexEnvf(GL_TEXTURE_ENV,GL_TEXTURE_ENV_MODE,GL_REPLACE);

改进 Phong镜面反射的颜色是光源的颜色，高光不依赖纹理

glTexEnvf(GL_TEXTURE_ENV,GL_TEXTURE_ENV_MODE,GL_MODULATE) ;

8_5_4例子的代码如下：

//RGBpixmap.h #ifndef _RGBPIXMAP #define _RGBPIXMAP #include <fstream> #include <iostream> #include <string> using namespace std; #include <windows.h> #include <assert.h> #include <math.h> #include <gl/GL.h> #include <gl/Glu.h> #include <gl/glut.h> class IntPoint { public: int x,y; void set(int dx,int dy){x=dx,y=dy;} void set(IntPoint& p){x=p.x;y=p.y;} IntPoint(int xx,int yy){x=xx;y=yy;} IntPoint(){x=y=0;} }; class IntRect { public: int left,top,right,bott; IntRect(){left=top=right=bott=0;} IntRect(int l,int t,int r,int b) {left=l; top=t; right=r;bott=b;} void set(int l,int t,int r,int b) {left=l;top=t;right=r;bott=b;} void set(IntRect& r){left=r.left;top=r.top;right=r.right;bott=r.bott;} }; typedef unsigned char uchar; class mRGB { public: uchar r,g,b; mRGB(){r=g=b=0;} mRGB(mRGB& p){r=p.r;g=p.g;b=p.b;} mRGB(uchar rr,uchar gg,uchar bb){r=rr;g=gg;b=bb;} }; class RGBpixmap { private: public: mRGB* pixel; // mRGB* numPixel; int nRows,nCols; void makeCheckerboard(); void setTexture(GLint textureName); RGBpixmap(){nRows=nCols=0;pixel=0;} RGBpixmap(int rows,int cols) { nRows=rows; nCols=cols; pixel=new mRGB[rows* cols]; } int readBMPFile(string fname); void freeIt() { delete []pixel; nRows=nCols=0; } void copy(IntPoint from,IntPoint to,int x,int y,int width,int height) { if(nRows==0||nCols==0)return; glCopyPixels(x,y,width,height,GL_COLOR); //复制像素 } void draw() { if(nRows==0||nCols==0)return; //通知OpenGL：不要在内存中对像素进行4字节边界对齐 glPixelStorei(GL_UNPACK_ALIGNMENT,1); glDrawPixels(nCols,nRows,GL_RGB,GL_UNSIGNED_BYTE,pixel); //往framebuffer写入像素 } int read(int x,int y,int wid,int ht) { nRows=ht; nCols=wid; pixel=new mRGB[nRows*nCols]; if(!pixel)return -1; glPixelStorei(GL_PACK_ALIGNMENT,1); //设置存储像素模式 glReadPixels(x,y,nCols,nRows,GL_RGB,GL_UNSIGNED_BYTE,pixel); //从 framebuffer读取像素 return 0; } int read(IntRect r) { nRows=r.top-r.bott; nCols=r.right-r.left; pixel=new mRGB[nRows*nCols]; if(!pixel)return -1; glPixelStorei(GL_PACK_ALIGNMENT,1); glReadPixels(r.left,r.bott,nCols,nRows,GL_RGB,GL_UNSIGNED_BYTE,pixel); return 0; } void setPixel(int x,int y,mRGB color) { if(x>=0 && x<nCols && y>=0 &&y<nRows) pixel[nCols*y+x]=color; } mRGB getPixel(int x,int y) { mRGB bad(255,255,255); assert(x>=0 && x<nCols); assert(y>=0 && y<nRows); return pixel[nCols*y+x]; } }; #endif //RGBpixmap.cpp #include "RGBpixmap.h" typedef unsigned short ushort; typedef unsigned long ulong; fstream inf; ushort getShort() //辅助函数 { //使用低位在前存储方式整型的BMP格式 //获取一个低位在前存储方式的2字节整数 char ic; ushort ip; inf.get(ic); ip=ic; //第一字节是低位 inf.get(ic); ip|=((ushort)ic<<8); //或在高字节 return ip; } ulong getLong() { ulong ip=0; char ic=0; unsigned char uc=ic; inf.get(ic);uc=ic;ip=uc; inf.get(ic);uc=ic;ip|=((ulong)uc<<8); inf.get(ic);uc=ic;ip|=((ulong)uc<<16); inf.get(ic);uc=ic;ip|=((ulong)uc<<24); return ip; } int RGBpixmap::readBMPFile(string fname) { //从未压缩的BMP文件中读入mRGB图像到内存中 //失败返回0，成功返回1 inf.open(fname.c_str(),ios::in|ios::binary); //读二进制字符串 if(!inf){cout<<"Can't open file:"<<fname<<endl;return 0;} int k,row,col,numPadBytes,nBytesInRow; //读入文件头信息 char ch1,ch2; inf.get(ch1);inf.get(ch2); //类型：总是'BM' ulong fileSize=getLong(); ushort reserved1=getShort(); //总是0 ushort reserved2=getShort(); //总是0 ulong offBits=getLong(); //到图像数据的偏移量-不可靠 ulong headerSize=getLong(); //总是40 ulong numCols=getLong(); //图像中列数 ulong numRows=getLong(); //图像中行数 ushort planes=getShort(); //总是1 ushort bitsPerPixel=getShort(); //8或24；这里允许是24 ulong compression=getLong(); //对未压缩的图片必须是0 ulong imageSize=getLong(); //图像的总字节数 ulong xpels=getLong(); //总是0 ulong ypels=getLong(); //总是0 ulong numLUTentries=getLong(); //对8位是256，否则为0 ulong impColors=getLong(); //总是0 if(bitsPerPixel!=24) { //必须是24位的未压缩图像 cout<<"not a 24 bit/pixelimage,or is compressed!/n"; inf.close();return 0; } //对每行加入若干字节以保证总字节数是4的倍数 //对3*numCols上舍入到4的倍数 nBytesInRow=((3*numCols+3)/4)*4; numPadBytes=nBytesInRow-3*numCols; //需要这么多 nRows=numRows; //设置类的数据成员 nCols=numCols; pixel=new mRGB[nRows*nCols]; //为数组申请空间 if(!pixel)return 0; //内存溢出 long count=0; char dum; char r,g,b; for(row=0;row<nRows;row++) //读入像素值 { for(col=0;col<nCols;col++) { inf.get(b);inf.get(g);inf.get(r); //读入字节 pixel[count].r=r; //设置颜色 pixel[count].g=g; pixel[count++].b=b; } for(k=0;k<numPadBytes;k++) //跳过行尾的扩充字节 inf>>dum; } inf.close(); return 1; //成功 } void RGBpixmap::makeCheckerboard() { nRows=nCols=64; //产生24*24的矩阵 pixel=new mRGB[3*nRows*nCols]; //不知道为什么要乘以三 if(!pixel){cout<<"out of memory!";return;} long count=0; for(int i=0;i<nRows;i++) for(int j=0;j<nCols;j++) { int c=(((i/8)+(j/8))%2)*255; pixel[count].r=c; pixel[count].g=c; pixel[count++].b=0; } } void RGBpixmap::setTexture(GLint textureName) { glBindTexture(GL_TEXTURE_2D,textureName); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST); glTexImage2D(GL_TEXTURE_2D,0,GL_RGB,nCols,nRows,0,GL_RGB,GL_UNSIGNED_BYTE,pixel);//设置二维纹理 } //texture.cpp #include <windows.h> #include "gl/gl.h" #include "gl/glu.h" #include "gl/glut.h" #include "RGBpixmap.h" RGBpixmap pix[6]; float xSpeed=0.2, ySpeed=0.5, xAngle=0.02, yAngle=0.02; void myInit(void) { glClearColor(1.0f,1.0f,1.0f,1.0f); glEnable(GL_DEPTH_TEST); glEnable(GL_TEXTURE_2D); pix[0].makeCheckerboard(); pix[0].setTexture(2001); pix[1].readBMPFile("Mandrill.bmp"); pix[1].setTexture(2002); pix[2].readBMPFile("Mandrill.bmp"); pix[2].setTexture(2003); pix[3].makeCheckerboard(); pix[3].setTexture(2004); pix[4].readBMPFile("red.bmp"); pix[4].setTexture(2005); pix[5].makeCheckerboard(); pix[5].setTexture(2006); glViewport(0,0,640,480); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(60.0,1280.0/800.0,1.0,30.0); //透视投影 glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glTranslated(0.0,-0.2,-4); } void display(void) { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glTexEnvf(GL_TEXTURE_ENV,GL_TEXTURE_ENV_MODE,GL_DECAL/*GL_REPLACEGL_MODULATE*/); //纹理调和 glPushMatrix(); glRotated(xAngle,1.0,0.0,0.0); glRotated(yAngle,0.0,1.0,0.0); glBindTexture(GL_TEXTURE_2D,2001); glBegin(GL_QUADS); glTexCoord2f(-1.0,-1.0);glVertex3f(-1.0f,1.0f,-1.0f); glTexCoord2f(-1.0,2.0);glVertex3f(-1.0f,1.0f,1.0f); glTexCoord2f(2.0,2.0);glVertex3f(1.0f,1.0f,1.0f); glTexCoord2f(2.0,-1.0);glVertex3f(1.0f,1.0f,-1.0f); glEnd(); glBindTexture(GL_TEXTURE_2D,2002); glBegin(GL_QUADS); glTexCoord2f(0.0,0.0);glVertex3f(1.0f,-1.0f,1.0f); glTexCoord2f(0.0,2.0);glVertex3f(1.0f,-1.0f,-1.0f); glTexCoord2f(2.0,2.0);glVertex3f(1.0f,1.0f,-1.0f); glTexCoord2f(2.0,0.0);glVertex3f(1.0f,1.0f,1.0f); glEnd(); glBindTexture(GL_TEXTURE_2D,2003); glBegin(GL_QUADS); glTexCoord2f(0.0,0.0);glVertex3f(-1.0f,1.0f,-1.0f); glTexCoord2f(2.0,0.0);glVertex3f(-1.0f,1.0f,1.0f); glTexCoord2f(2.0,2.0);glVertex3f(-1.0f,-1.0f,1.0f); glTexCoord2f(0.0,2.0);glVertex3f(-1.0f,-1.0f,-1.0f); glEnd(); glBindTexture(GL_TEXTURE_2D,2004); glBegin(GL_QUADS); glTexCoord2f(1.0,0.0);glVertex3f(1.0f,-1.0f,1.0f); glTexCoord2f(1.0,1.0);glVertex3f(1.0f,-1.0f,-1.0f); glTexCoord2f(0.0,1.0);glVertex3f(-1.0f,-1.0f,-1.0f); glTexCoord2f(0.0,0.0);glVertex3f(-1.0f,-1.0f,1.0f); glEnd(); glBindTexture(GL_TEXTURE_2D,2005); glBegin(GL_QUADS); glTexCoord2f(0.0,2.0);glVertex3f(1.0f,1.0f,1.0f); glTexCoord2f(2.0,0.0);glVertex3f(1.0f,-1.0f,1.0f); glTexCoord2f(0.0,-2.0);glVertex3f(-1.0f,-1.0f,1.0f); glTexCoord2f(-2.0,0.0);glVertex3f(-1.0f,1.0f,1.0f); glEnd(); glBindTexture(GL_TEXTURE_2D,2006); glBegin(GL_QUADS); glTexCoord2f(1.0,0.0);glVertex3f(-1.0f,1.0f,-1.0f); glTexCoord2f(1.0,0.0);glVertex3f(1.0f,1.0f,-1.0f); glTexCoord2f(1.0,0.0);glVertex3f(1.0f,-1.0f,-1.0f); glTexCoord2f(1.0,0.0);glVertex3f(-1.0f,-1.0f,-1.0f); glEnd(); glFlush(); glPopMatrix(); glutSwapBuffers(); glutPostRedisplay(); //何解？ } void spinner(void) //空闲函数 { xAngle+=xSpeed; yAngle+=ySpeed; display(); } void main(int argc,char **argv) { glutInit(&argc,argv); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB); glutInitWindowSize(1280,800); glutInitWindowPosition(0,0); glutCreateWindow("Rotating Cube Demo"); glutDisplayFunc(display); myInit(); glutIdleFunc(spinner); glutMainLoop(); }

运行结果如下：

 

 

新学过的接口函数：

glPixelStorei(GL_UNPACK_ALIGNMENT,1);

glDrawPixels(nCols,nRows,GL_RGB,GL_UNSIGNED_BYTE,pixel);

glReadPixels(x,y,nCols,nRows,GL_RGB,GL_UNSIGNED_BYTE,pixel);

glutPostRedisplay();

glBindTexture(GL_TEXTURE_2D,textureName);

       glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);

       glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST);

       glTexImage2D(GL_TEXTURE_2D,0,GL_RGB,nCols,nRows,0,GL_RGB,GL_UNSIGNED_BYTE,pixel);

glutIdleFunc(spinner);

glHint(GL_PERSPECTIVE,GL_NICEST);

//此函数要求OpenGL正确的（使双曲线插值）渲染纹理，这样当面片相对观察者旋转地时候，纹理才会正确的贴在面片之上

 

反射映射

铬映射 chrome mapping

环境映射 environment mapping

 

 

对于纹理包裹在一个大的包围立方体的情况，OpenGL提供了进行这种近似环境映射的工具

glTexGenf(GL_S,GL_TEXTURE_GEN_MODE,GL_CUBE_MAP) ;

glTexGenf(GL_T,GL_TEXTURE_GEN_MODE,GL_CUBE_MAP) ;

glEnable(GL_TEXTURE_GEN_S);

glEnable(GL_TEXTURE_GEN_T) ;