#100317#NeHe学习笔记---添加纹理

首先是在框架中添加了几个变量：
GLfloatxrot;       
GLfloatyrot;       
GLfloatzrot;      
GLuinttexture[1];     //用于存储纹理的数据结构

然后添加了一个用于读取图像的函数：
AUX_RGBImageRec *LoadBMP(char *Filename)    // Loads A Bitmap Image
{
 FILE *File=NULL;         // File Handle

 if (!Filename)          // Make Sure A Filename Was Given
 {
  return NULL;         // If Not Return NULL
 }

 File=fopen(Filename,"r");       // Check To See If The File Exists

 if (File)           // Does The File Exist?
 {
  fclose(File);         // Close The Handle
  return auxDIBImageLoad(Filename);    // Load The Bitmap And Return A Pointer
 }

 return NULL;          // If Load Failed Return NULL
}

又添加了一个用于装载纹理的函数：

int LoadGLTextures()         // Load Bitmaps And Convert To Textures
{
 int Status=FALSE;         // Status Indicator

 AUX_RGBImageRec *TextureImage[1];     // Create Storage Space For The Texture

 memset(TextureImage,0,sizeof(void *)*1);            // Set The Pointer To NULL

 // Load The Bitmap, Check For Errors, If Bitmap's Not Found Quit
 if (TextureImage[0]=LoadBMP("Data/NeHe.bmp"))
 {
  Status=TRUE;         // Set The Status To TRUE

  glGenTextures(1, &texture[0]);     // Create The Texture

  // Typical Texture Generation Using Data From The Bitmap
  glBindTexture(GL_TEXTURE_2D, texture[0]);
  glTexImage2D(GL_TEXTURE_2D, 0, 3, TextureImage[0]->sizeX, TextureImage[0]->sizeY, 0, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[0]->data);
  glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
 }

 if (TextureImage[0])         // If Texture Exists
 {
  if (TextureImage[0]->data)       // If Texture Image Exists
  {
   free(TextureImage[0]->data);     // Free The Texture Image Memory
  }

  free(TextureImage[0]);        // Free The Image Structure
 }

 return Status;          // Return The Status
}

即是如何用图像生成纹理的。

 

再修改int InitGL(GLvoid)函数，使纹理设置生效：

 

      int InitGL(GLvoid)          // All Setup For OpenGL Goes Here
{
 if (!LoadGLTextures())        // Jump To Texture Loading Routine ( NEW )
 {
  return FALSE;         // If Texture Didn't Load Return FALSE
 }

 glEnable(GL_TEXTURE_2D);       // Enable Texture Mapping ( NEW )
 glShadeModel(GL_SMOOTH);       // Enable Smooth Shading
 glClearColor(0.0f, 0.0f, 0.0f, 0.5f);    // Black Background
 glClearDepth(1.0f);         // Depth Buffer Setup
 glEnable(GL_DEPTH_TEST);       // Enables Depth Testing
 glDepthFunc(GL_LEQUAL);        // The Type Of Depth Testing To Do
 glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST); // Really Nice Perspective Calculations
 return TRUE;          // Initialization Went OK
}

最后

int DrawGLScene(GLvoid)         // Here's Where We Do All The Drawing
{
 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear The Screen And The Depth Buffer
 glLoadIdentity();         // Reset The View
 glTranslatef(0.0f,0.0f,-5.0f);

 glRotatef(xrot,1.0f,0.0f,0.0f);
 glRotatef(yrot,0.0f,1.0f,0.0f);
 glRotatef(zrot,0.0f,0.0f,1.0f);

 glBindTexture(GL_TEXTURE_2D, texture[0]);                   //？？可选，注释后运行无障碍。

 glBegin(GL_QUADS);
  // Front Face
  glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);
  glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);
  glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f,  1.0f);
  glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f,  1.0f);
  // Back Face
  glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);
  glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);
  glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);
  glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f);
  // Top Face
  glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);
  glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f,  1.0f,  1.0f);
  glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f,  1.0f,  1.0f);
  glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);
  // Bottom Face
  glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, -1.0f, -1.0f);
  glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f, -1.0f, -1.0f);
  glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);
  glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);
  // Right face
  glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f);
  glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);
  glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  1.0f,  1.0f);
  glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);
  // Left Face
  glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);
  glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);
  glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  1.0f,  1.0f);
  glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);
 glEnd();

 xrot+=0.3f;
 yrot+=0.2f;
 zrot+=0.4f;
 return TRUE;          // Keep Going
}

（0.0f，0.0f）是左下的坐标，其余的类似设置来改变纹理的方向。