OpenGL学习十：视口，正投影，透视投影
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正投影是以原比例进行显示不会随着Z轴的变化而变化
视口：viewport当我们投影完成以后投影内容会按照视口的比例进行拉伸和缩放
举例：视口的大小是800*600? 假设我们正投影设置为 width 8 height 6 那么显示出来的效果就是物体宽高都拉伸100倍
?glViewport(0,0,800,600);
?glOrtho(0,200,0,150,-1,1);
?glBegin(GL_QUADS);
?glTexCoord2f(0.0f, 0.0f); glVertex3f(0, 0,? 0);
?glTexCoord2f(1.0f,0.0f); glVertex3f(100, 0,? 0);
?glTexCoord2f(1.0f,1.0f);glVertex3f(100,? 100,? 0);
?glTexCoord2f(0.0f,1.0f);glVertex3f(0,? 100,? 0);
?glEnd(）
分析：可知四边形宽度和高度都是100，乘以系数 分别为weight(100*800/200),height(100*600/150)
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#include "header.h"GLuinttexture[3];AUX_RGBImageRec *LoadBMP(char *Filename) {FILE *File=NULL; if (!Filename) {return NULL; }File=fopen(Filename,"r"); if (File) {fclose(File); return auxDIBImageLoad(Filename); }return NULL; }int LoadGLTextures() {int Status=FALSE; AUX_RGBImageRec *TextureImage[3]; memset(TextureImage,0,sizeof(void *)*3); if ((TextureImage[0]=LoadBMP("Data/logo.bmp") )&& (TextureImage[1]=LoadBMP("Data/mask1.bmp"))&& (TextureImage[2]=LoadBMP("Data/image1.bmp"))){Status=TRUE; glGenTextures(3, &texture[0]); glBindTexture(GL_TEXTURE_2D, texture[0]);glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, TextureImage[0]->sizeX, TextureImage[0]->sizeY, 0, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[0]->data);glBindTexture(GL_TEXTURE_2D, texture[1]);glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, TextureImage[1]->sizeX, TextureImage[1]->sizeY, 0, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[1]->data);glBindTexture(GL_TEXTURE_2D, texture[2]);glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, TextureImage[2]->sizeX, TextureImage[2]->sizeY, 0, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[2]->data);}if (TextureImage[0]) {if (TextureImage[0]->data) {free(TextureImage[0]->data); }free(TextureImage[0]); }return Status; }GLvoid ReSizeGLScene(GLsizei width, GLsizei height){if (height==0){height=1;}glViewport(0,0,600,480);glMatrixMode(GL_PROJECTION);glLoadIdentity();gluPerspective(90.0f,(GLfloat)600/(GLfloat)480,0.1f,100.0f);glMatrixMode(GL_MODELVIEW);glLoadIdentity();}int InitGL(GLvoid){if (!LoadGLTextures()){return FALSE;}glClearColor(1.0f, 1.0f, 1.0f, 0.0f);glClearDepth(1.0);glEnable(GL_DEPTH_TEST);//glShadeModel(GL_SMOOTH);glEnable(GL_TEXTURE_2D);return TRUE;}void DrawGLScene(GLvoid){glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);glLoadIdentity();glTranslatef(0.0f,0.0f,-3.0f);glBindTexture(GL_TEXTURE_2D, texture[0]);glColor3f(1.0f,1.0f,0.0f);glBegin(GL_QUADS);glTexCoord2f(0.0f, 0.0f); glVertex3f(0.0f,0.0f,0.0f);glTexCoord2f(1.0f,0.0f);glVertex3f(1.0f, 0.0f,0.0f);glTexCoord2f(1.0f,1.0f);glVertex3f(1.0f, 1.0f, 0.0f);glTexCoord2f(0.0f,1.0f);glVertex3f(0.0f, 1.0f, 0.0f);glEnd();glMatrixMode(GL_PROJECTION); glPushMatrix(); glLoadIdentity();glOrtho(0,800,0,600,-1,1);glMatrixMode(GL_MODELVIEW);glPushMatrix(); glLoadIdentity();glColor3f(0.0f,1.0f,0.0f);glBegin(GL_QUADS);glTexCoord2f(0.0f, 0.0f); glVertex3i(10, 30, 0);glTexCoord2f(1.0f,0.0f);glVertex3i(110, 30, 0);glTexCoord2f(1.0f,1.0f);glVertex3i(110, 130, 0);glTexCoord2f(0.0f,1.0f);glVertex3i(10, 130, 0);glEnd();glMatrixMode(GL_PROJECTION); glPopMatrix(); glMatrixMode(GL_MODELVIEW); glPopMatrix(); glMatrixMode(GL_PROJECTION);glPushMatrix(); glLoadIdentity();glOrtho(0,800,600,0,-1,1);glMatrixMode(GL_MODELVIEW);glPushMatrix(); glLoadIdentity();glScaled(2,2,2);glColor3f(1.0f,0.0f,0.0f);glBegin(GL_QUADS);glTexCoord2f(0.0f, 0.0f);glVertex3i(10, 30, 0);glTexCoord2f(1.0f,0.0f);glVertex3i(110, 30, 0);glTexCoord2f(1.0f,1.0f);glVertex3i(110, 130, 0);glTexCoord2f(0.0f,1.0f);glVertex3i(10, 130, 0);glEnd();glMatrixMode(GL_PROJECTION); glPopMatrix(); glMatrixMode(GL_MODELVIEW); glPopMatrix(); glMatrixMode(GL_PROJECTION);glPushMatrix(); glLoadIdentity();glOrtho(800,0,600,0,-1,1);glMatrixMode(GL_MODELVIEW);glPushMatrix(); glLoadIdentity();glColor3f(0.8f,0.5f,0.0f);glBegin(GL_QUADS);glTexCoord2f(0.0f, 0.0f);glVertex3i(10, 30, 0);glTexCoord2f(1.0f,0.0f);glVertex3i(110, 30, 0);glTexCoord2f(1.0f,1.0f);glVertex3i(110, 130, 0);glTexCoord2f(0.0f,1.0f);glVertex3i(10, 130, 0);glEnd();glMatrixMode(GL_PROJECTION); glPopMatrix(); glMatrixMode(GL_MODELVIEW); glPopMatrix(); glMatrixMode(GL_PROJECTION);glPushMatrix(); glLoadIdentity();glOrtho(800,0,0,600,-1,1);glMatrixMode(GL_MODELVIEW);glPushMatrix(); glLoadIdentity();glColor3f(0.3f,0.5f,1.0f);glBegin(GL_QUADS);glTexCoord2f(0.0f, 0.0f);glVertex3i(10, 30, 0);glTexCoord2f(1.0f,0.0f);glVertex3i(110, 30, 0);glTexCoord2f(1.0f,1.0f);glVertex3i(110, 130, 0);glTexCoord2f(0.0f,1.0f);glVertex3i(10, 130, 0);glEnd();glMatrixMode(GL_PROJECTION); glPopMatrix(); glMatrixMode(GL_MODELVIEW); glPopMatrix();glFlush();}int main(int argc, char** argv){glutInit(&argc, argv);glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);glutInitWindowSize(640,480);glutCreateWindow("视口，正投影，透视投影");glutReshapeFunc(ReSizeGLScene);glutDisplayFunc(DrawGLScene);InitGL();glutMainLoop();return 0;}?