如何将纹理应用到四边形以纹理立方体？
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【中文标题】如何将纹理应用到四边形以纹理立方体？【英文标题】：How to apply textures to a quad in order to texture a cube? 【发布时间】：2010-07-17 11:34:40 【问题描述】：最近我一直在研究 OpenGL，如果我想对事物进行纹理处理，我已经上台了。我想我会从纹理一个简单的立方体开始。 我目前有这段代码，并且完全理解它是如何工作的：
#include <glut.h>
#define WINDOW_WIDTH 400
#define WINDOW_HEIGHT 400
float angle = 30.0f;
void Draw()
glLoadIdentity(); //Reset the drawing perspective
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //Clears the buffers
//Add positioned light
GLfloat lightColor0[] = 0.5f, 0.5f, 0.5f, 1.0f; //Color intensity
GLfloat lightPos0[] = 0.0f, 0.0f, 0.0f, 1.0f; //Positioned at..
glLightfv(GL_LIGHT0, GL_DIFFUSE, lightColor0); //Set our light colour
glLightfv(GL_LIGHT0, GL_POSITION, lightPos0); //Set our light position
glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, 200);
glRotatef(angle,1.0f,1.0f,1.0f); //Rotate around the origin
glScalef(0.4f, 0.4f, 0.4f); //Scale the shape down
glBegin(GL_QUADS); //Start drawing a Quad
glColor3f(1.0f,0.0f,0.0f); //Set the colour to Red
glVertex3f( 1.0f, 1.0f,-1.0f); //Top right of the quad (Top Face)
glVertex3f(-1.0f, 1.0f,-1.0f); //Top left of the quad (Top Face)
glVertex3f(-1.0f, 1.0f, 1.0f); //Bottom left of the quad (Top Face)
glVertex3f( 1.0f, 1.0f, 1.0f); //Bottom right of the quad (Top Face)
glVertex3f( 1.0f,-1.0f, 1.0f); //Top right of the quad (Bottom Face)
glVertex3f(-1.0f,-1.0f, 1.0f); //Top left of the quad (Bottom Face)
glVertex3f(-1.0f,-1.0f,-1.0f); //Bottom left of the quad (Bottom Face)
glVertex3f( 1.0f,-1.0f,-1.0f); //Bottom right of the quad (Bottom Face)
glVertex3f( 1.0f, 1.0f, 1.0f); //Top right of the quad (Front Face)
glVertex3f(-1.0f, 1.0f, 1.0f); //Top left of the quad (Front Face)
glVertex3f(-1.0f,-1.0f, 1.0f); //Bottom left of the quad (Front Face)
glVertex3f( 1.0f,-1.0f, 1.0f); //Bottom right of the quad (Front Face)
glVertex3f( 1.0f,-1.0f,-1.0f); //Top right of the quad (Back Face)
glVertex3f(-1.0f,-1.0f,-1.0f); //Top left of the quad (Back Face)
glVertex3f(-1.0f, 1.0f,-1.0f); //Bottom left of the quad (Back Face)
glVertex3f( 1.0f, 1.0f,-1.0f); //Bottom right of the quad (Back Face)
glVertex3f(-1.0f, 1.0f, 1.0f); //Top right of the quad (Left Face)
glVertex3f(-1.0f, 1.0f,-1.0f); //Top left of the quad (Left Face)
glVertex3f(-1.0f,-1.0f,-1.0f); //Bottom left of the quad (Left Face)
glVertex3f(-1.0f,-1.0f, 1.0f); //Bottom right of the quad (Left Face)
glVertex3f( 1.0f, 1.0f,-1.0f); //Top right of the quad (Right Face)
glVertex3f( 1.0f, 1.0f, 1.0f); //Top left of the quad (Right Face)
glVertex3f( 1.0f,-1.0f, 1.0f); //Bottom left of the quad (Right Face)
glVertex3f( 1.0f,-1.0f,-1.0f); //Bottom right of the quad (Right Face)
glEnd(); //Finished Drawing The Quad
glutSwapBuffers(); //Send the 3D scene to the screen
void Update(int value) //Our update function
angle+=0.5f; //Increase the angle by 5
if(angle>360) //If the angle is greater than 360
angle=0; //Set the angle to 0
glutPostRedisplay(); //Tell it that the scene has changed
glutTimerFunc(25,Update,0); //Call "Update" again in another 25ms
void Initialize()
glEnable(GL_DEPTH_TEST);
glEnable(GL_COLOR_MATERIAL);
glEnable(GL_LIGHTING); //Enable lighting
glEnable(GL_LIGHT0); //Enable light No. 0
glEnable(GL_NORMALIZE); //Automatically "normalize" normals
glShadeModel(GL_SMOOTH); //Enable smooth shading (nice effect)
glClearColor(0.0, 0.0, 0.0, 0.0); //Background RGBA
glMatrixMode(GL_MODELVIEW); //MODELVIEW view
glLoadIdentity(); //Start at origin
glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0); //Set the scale
//X axis = 0 to 1. Y = 0 to 1. Z = -1 to 1.
int main()
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH); //The display mode
glutInitWindowSize(WINDOW_WIDTH, WINDOW_HEIGHT); //Window Size
glutInitWindowPosition(200, 200); //Window Position
glutCreateWindow("Lighting!"); //Creates a window with the name "Lighting!"
Initialize(); //Call our initialize function.
glutDisplayFunc(Draw); //"Draw" then refresh the window
glutTimerFunc(25,Update,0); //Call "Update" 25ms after program starts
glutMainLoop(); //Process events etc. Also keeps the window open.
return 0; //End the program
然而，在阅读了很多很多纹理教程之后（我的意思是我可以在网上找到的所有教程）；我仍然对如何将其添加到该程序中感到困惑。 我知道我必须（以某种方式）加载纹理，然后在绘制立方体之前使用 glBindTexture 函数绑定它，但我认为在这两者之间我还需要做一些其他事情（而且我不知道如何加载图像也正确）。
【问题讨论】：
【参考方案1】：要加载纹理文件（png、jpg...），请使用以下命令： （别忘了安装 SDL 和 SDL_image 库）
#include <SDL/SDL.h>
#include <SDL/SDL_image.h>
GLuint texture_alloc(const char *tex_name, int alpha)
GLuint tex_num;
SDL_Surface *tex_img;
glGenTextures(1, &tex_num);
if(tex_img = (SDL_Surface *) IMG_Load(tex_name))
glBindTexture(GL_TEXTURE_2D, tex_num);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE);
if (alpha==1)
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, tex_img->w, tex_img->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, tex_img->pixels);
else
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, tex_img->w, tex_img->h, 0, GL_RGB, GL_UNSIGNED_BYTE, tex_img->pixels);
SDL_FreeSurface (tex_img);
return tex_num;
使用 glTexCoord 函数设置纹理坐标：
glTexCoord2f(0.0f, 0.0f);
glVertex3f( 1.0f, 1.0f,-1.0f);
glTexCoord2f(1.0f, 0.0f);
glVertex3f(-1.0f, 1.0f,-1.0f);
.
.
.
【讨论】：
+ 你可以将 (alpha==1) 替换为 (tex_img->format->BitsPerPixel==32) /RGBA/【参考方案2】：我建议查看SOIL，一个 OpenGL 图像加载库 - 我使用它。
就纹理的工作而言，它几乎是：
Unsigned int texture = SOIL_load_OGL_texture(imagePath.c_str(), SOIL_CREATE_NEW_ID, SOIL_LOAD_AUTO, SOIL_FLAG_MIPMAPS);
glBindTexture(texture);
但是，您必须使用纹理坐标，以便 opengl 知道如何包装您的纹理。下面是一些渲染立方体的示例调用。
int size = 1;
// Begin Rending
glBegin(GL_QUADS);
// Face 1
glNormal3f( 0.0f, 0.0f, 1.0f);
glTexCoord2f(0.0f, 0.0f);
glVertex3f( m_size, m_size,-m_size);
glTexCoord2f(1.0f, 0.0f);
glVertex3f(-m_size, m_size,-m_size);
glTexCoord2f(1.0f, 1.0f);
glVertex3f(-m_size, m_size, m_size);
glTexCoord2f(0.0f, 1.0f);
glVertex3f( m_size, m_size, m_size);
// Face 2
glNormal3f( 0.0f, 0.0f,-1.0f);
glTexCoord2f(0.0f, 0.0f);
glVertex3f( m_size,-m_size, m_size);
glTexCoord2f(1.0f, 0.0f);
glVertex3f(-m_size,-m_size, m_size);
glTexCoord2f(1.0f, 1.0f);
glVertex3f(-m_size,-m_size,-m_size);
glTexCoord2f(0.0f, 1.0f);
glVertex3f( m_size,-m_size,-m_size);
// Face 3
glTexCoord2f(0.0f, 0.0f);
glVertex3f( m_size, m_size, m_size);
glTexCoord2f(1.0f, 0.0f);
glVertex3f(-m_size, m_size, m_size);
glTexCoord2f(1.0f, 1.0f);
glVertex3f(-m_size,-m_size, m_size);
glTexCoord2f(0.0f, 1.0f);
glVertex3f( m_size,-m_size, m_size);
// Face 4
glNormal3f( 0.0f,-1.0f, 0.0f);
glTexCoord2f(0.0f, 0.0f);
glVertex3f( m_size,-m_size,-m_size);
glTexCoord2f(1.0f, 0.0f);
glVertex3f(-m_size,-m_size,-m_size);
glTexCoord2f(1.0f, 1.0f);
glVertex3f(-m_size, m_size,-m_size);
glTexCoord2f(0.0f, 1.0f);
glVertex3f( m_size, m_size,-m_size);
// Face 5
glNormal3f( 1.0f, 0.0f, 0.0f);
glTexCoord2f(0.0f, 0.0f);
glVertex3f(-m_size, m_size, m_size);
glTexCoord2f(1.0f, 0.0f);
glVertex3f(-m_size, m_size,-m_size);
glTexCoord2f(1.0f, 1.0f);
glVertex3f(-m_size,-m_size,-m_size);
glTexCoord2f(0.0f, 1.0f);
glVertex3f(-m_size,-m_size, m_size);
// Face 6
glNormal3f( 1.0f, 0.0f, 0.0f);
glTexCoord2f(0.0f, 0.0f);
glVertex3f( m_size, m_size,-m_size);
glTexCoord2f(1.0f, 0.0f);
glVertex3f( m_size, m_size, m_size);
glTexCoord2f(1.0f, 1.0f);
glVertex3f( m_size,-m_size, m_size);
glTexCoord2f(0.0f, 1.0f);
glVertex3f( m_size,-m_size,-m_size);
glEnd();
【讨论】：
【参考方案3】：我认为您缺少的部分是纹理坐标的概念。
纹理是二维的吧？因此，当您将对象的 3d 点推送到图形卡时，如果您希望它具有纹理，您还需要将该 3d 点与纹理图像中的位置相关联，您可以使用一对纹理坐标（配对因为纹理是 2d)... 看看 glTexCoord2f()... 如果您在调用 glVertex3f() 之前调用它，您会将该 3d 点与图像中的一个点相关联... 如果您对构成原始 opengl 的所有点执行此操作，可以对中间的所有点进行插值...
【讨论】：
所以我必须创建立方体（使用我程序中已有的绘制代码），然后使用我的 Tomas Cokis 帖子中的大部分代码映射纹理？ 是的。您创建一个纹理，将图像加载到其中（我认为使用 glTexSubImage2d()），然后使用 glBindTexture() 以便openGL知道您在谈论什么纹理，然后当您推动几何图形时，您也会推动纹理坐标（使用glTexCoord2f()). 好的，我想我明白了。但是您说要使用 hlTexSubImage2d() 加载图像，但是根据快速搜索，该函数没有文件路径参数；那么我如何实际加载图像？ （我知道我可以使用 SOIL，但我通常不喜欢额外的预先创建的标头，如果可能的话，我更愿意以纯 OpenGL 的方式进行）。 是的，glTexSubImage2d() 不知道图像文件...您必须为其提供指向充满像素的缓冲区的指针... OpenGL 对文件一无所知。【参考方案4】：对于图像加载，您还可以使用 SDL 图像库：
http://www.libsdl.org/projects/SDL_image/
非常方便。
【讨论】：
我认为该库仅用于 SDL 的内置渲染？ 不，它是你想要的任何东西的扩展，当然，它可能需要 sdl（我不知道）但你可以在任何地方使用它【参考方案5】：您可以使用http://nehe.gamedeve.net/ 中的 glaux 代码，这也很简单。
AUX_RGBImageRec* LoadBMP(char* Filename)
FILE *File = NULL;
if ( !Filename )
return NULL;
File = fopen(Filename,"r");
if ( !Filename )
return NULL;
fclose(File);
return auxDIBImageLoad(Filename);
int LoadTextures()
int Status = FALSE;
AUX_RGBImageRec *TextureImage[1];
memset(TextureImage,0,sizeof(void*)*1);
if ( TextureImage[0] = LoadBMP("GoneFishing.bmp") )
Status = true;
if(texture[0] == -1)
glGenTextures(1,&texture[0]);
glBindTexture(GL_TEXTURE_2D,texture[0]);
// Generate The Texture
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); // Linear Filtering
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); // Linear Filtering
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;
【讨论】：
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