OpenGL小探3——纹理映射

纹理映射

纹理映射相关函数：

void glGenTextures(GLsizei n, GLuint *textures);

void glBindTexture(GLenum target, GLuint texture);

#include <stdio.h>

#include <GL/glaux.h> //在Qt中的头文件

GLfloat xrot; //x旋转量

GLfloat yrot;

GLfloat zrot;

GLuint texture[1]; //存储一个纹理

//位图宽高应是64,128,256像素

AUX_RGBImageRec *LoadBMP(char* FileName e){ //载入位图图像

FILE *File = NULL; //文件句柄

if(!e)

return NULL;

File = fopen(e,"r");

if(File) {

flose(File);

return auxDIBImageLoad(e);

}else

return NULL;

}

int LoadGLTextures(){ //载入位图并转换成纹理

int Status = FALSE;

AUX_RGBImageRec *TextureImage[1]; //存储纹理

memset(TextureImage,0,sizeof(void*)*1); //将指针设为NULL

if(TextureImage[0] = LoadBMP("Data.bmp")){

Status = TRUE;

glGenTextures(1,&texture[0]); //创建一个纹理

glBindTexture(GL_TEXTURE_2D,texture[0]); //&texture[0]绑定纹理

glTexImage2D(GL_TEXTURE_2D,0,3,TextureImage[0]->sizeX,TextureImage[0]->sizeY,

0,GL_RGB,GL_UNSIGNED_BYTE,TextureImage[0]->data); //生成纹理

glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);//线性滤波

glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);//线性滤波

}

if(TextureImage[0]){ //纹理是否存在

if(TextureImage[0]->data) { //纹理图像是否存在

free(TextureImage[0]->data);

}

free(TextureImage[0]); //释放图像结构

   }

return Status;

}

int InitGL(GLvoid){     //此处开始对OpenGL进行所有设置

if(!LoadGLTextures()){  //调用纹理载入子例程

return FALSE;       //载入失败

}

glEnable(GL_TEXTURE_2D); //启用纹理映射

glShadeModel(GL_SMOOTH);  //阴影平滑

glClearColor(0.0f,0.0f,0.0f,0.5f);  //黑色背景

glClearDepth(1.0f);   //设置深度缓存

glEnable(GL_DEPTH_TEST); //启用深度测试

glDepthFunc(GL_LEQUAL);  //深度测试的类型

glHint(GL_PERSPECTIVE_CORRECTION_HINT,GL_NICEST); //真正精细的透视修正

return TRUE;

}

int DrawGLScene(GLvoid){  //从这里开始进行所有的绘制

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //清除屏幕和深度缓存

glLoadIdentity();

glTranslatef(0.0f,0.0f,-5.0f); //移入屏幕5个单位

glRotate(xrot,1.0f,0.0f,0.0f);  //绕x轴旋转

glRotate(yrot,0.0f,1.0f,0.0f);

glRotate(zrot,0.0f,0.0f,1.0f);

glBindTexture(GL_TEXTURE_2D,texture[0]); //绑定纹理，不能在glBegin()和glEnd()之间

//为了将纹理正确的映射到四边形上，必须将纹理的右上角映射到四边形的右上角，如此等等。

//glTexCoord2f参数为x，y坐标：0.0f是纹理的左侧/底部，0.0f是中点，1.0f是纹理的右侧/顶部

glBegin(GL_QUADS);

//前面

glTexCoord2f(0.0f,0.0f); glVertex3f(-1.0f,-1.0f,1.0f); //纹理和四边形的左下

glTexCoord2f(1.0f,0.0f); glVertex3f(1.0f,-1.0f,1.0f);  //右下

glTexCoord2f(1.0f,1.0f); glVertex3f(1.0f,1.0f,1.0f); //右上

glTexCoord2f(0.0f,1.0f); glVertex3f(-1.0f,1.0f,1.0f); //左上

//后面

glTexCoord2f(1.0f,0.0f); glVertex3f(-1.0f,-1.0f,-1.0f); //右下

glTexCoord2f(1.0f,1.0f); glVertex3f(-1.0f,1.0f,-1.0f); //右上

glTexCoord2f(0.0f,1.0f); glVertex3f(1.0f,1.0f,-1.0f); //左上

glTexCoord2f(0.0f,0.0f); glVertex3f(1.0f,-1.0f,-1.0f); //左下

//顶面

glTexCoord2f(0.0f,1.0f); glVertex3f(-1.0f,1.0f,-1.0f); //左上

glTexCoord2f(0.0f,0.0f); glVertex3f(-1.0f,1.0f.1.0f); //左上

glTexCoord2f(1.0f,0.0f); glVertex3f(1.0f,1.0f,1.0f); //右下

glTexCoord2f(1.0f,1.0f); glVertex3f(1.0f,1.0f,-1.0f); //右上

//底面

glTexCoord2f(1.0f,1.0f); glVertex3f(1.0f,-1.0f,-1.0f); //右上

glTexCoord2f(0.0f,1.0f); glVertex3f(-1.0f,-1.0f,-1.0f); //左上

glTexCoord2f(0.0f,0.0f); glVertex3f(-1.0f,-1.0f,1.0f); //左下

glTexCoord2f(1.0f,0.0f); glVertex3f(1.0f,-1.0f,1.0f); //右下

//右面

glTexCoord2f(1.0f,0.0f); glVertex3f(1.0f,-1.0f,-1.0f); //右下

glTexCoord2f(0.0f,1.0f); glVertex3f(1.0f,1.0f,1.0f); //左上

glTexCoord2f(0.0f,0.0f); glVertex3f(1.0f,-1.0f,1.0f); //左下

glTexCoord2f(1.0f,0.0f); glVertex3f(1.0f,-1.0f,-1.0f); //右下

glEnd();

xrot += 0.3f;

yrot += 0.2f;

zrot += 0.4f;

return true;

}