正投影：将物体直接投影到屏幕上，不改变其大小
glOrtho (GLdouble left, GLdouble right, GLdouble bottom, GLdouble top, GLdouble zNear, GLdouble zFar);透视投影：远处的东西看起来要小一些,近处的东西看起来会大一些,这就是透视原理
gluPerspective(GLdouble fovy,GLdouble aspect,GLdouble zNear,GLdouble zFar)
首先得设置gluPerspective,来看看它的参数都表示什么意思
fovy,这个最难理解,我的理解是,眼睛睁开的角度,即,视角的大小,如果设置为0,相当你闭上眼睛了,所以什么也看不到,如果为180,那么可以认为你的视界很广阔,
aspect,这个好理解,就是实际窗口的纵横比,即x/y
zNear,这个呢,表示你近处剪裁面
zFar表示远处剪裁面
glViewport(0,0,600,480);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f,(GLfloat)600/(GLfloat)480,0.1f,100.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
窗口的大小是800*600 视口的大小是600*480,可以看出视口是以窗口的左下角为原点的一个区域
glTranslatef(0.0f,0.0f,-3.0f);
glBindTexture(GL_TEXTURE_2D, texture[0]);
glColor3f(1.0f,1.0f,0.0f);//黄色图形
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);//绿色图形
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();
建立right=800,top=600的正投影。可以看到正投影以左下角为原点（虽然视口是600*400，此处会按照比例进行缩放）
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);//红色图形
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()
建立right=800,bottom=600的正投影。可以看到正投影以左上角为原点（虽然视口是600*400，此处会按照比例进行缩放）glScaled可以对正投影进行缩放，glTranslatef可对透视投影进行缩放
建立left=800,bottom=600的正投影。可以看到正投影以右上角为原点
建立left=800,top=600的正投影。可以看到正投影以右上角为原点
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)
#include "header.h"
GLuint texture[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;
}
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