OpenGL - 渲染 3D 纹理答案

【问题标题】：OpenGL - render 3D textureOpenGL - 渲染 3D 纹理
【发布时间】：2016-04-27 14:17:37
【问题描述】：

想法： 我一直在尝试开发可以获取几（十）张 2D 图像并将它们渲染为 3D 纹理的代码。到目前为止，我根据我之前的帖子的建议使用了 glTexImage3D 和 glTexSubImage3D：OpenGL - 'glTexSubImage3D': identifier not found

我的工作基于 NeHe 的纹理映射教程：http://nehe.gamedev.net/tutorial/lesson_06_texturing_update/47002/

NeHe 教程main() 中的函数调用流程如下：CreateGLWindow()、InitGL()、LoadGLTextures()、DrawGLScene()。我只对从DrawGLScene() 开始的代码进行了更改，而该函数下方的所有内容都与我的代码中的相同。

问题： 代码中的所有内容看似看起来都正确，但是屏幕上没有呈现任何内容。我花了两天时间试图让它工作无济于事。我错过了什么？有什么我做错了吗？

编辑代码

#include "windows.h"        
#include "stdio.h"          
#include "gl\gl.h"          
#include "gl\glu.h"         
#include "GLext.h"
#include "SOIL.h"

HDC          hDC=NULL;      
HGLRC        hRC=NULL;      
HWND         hWnd=NULL;     
HINSTANCE    hInstance;     

bool    keys[256];          
bool    active=TRUE;        
bool    fullscreen=TRUE;    

GLfloat xrot;               
GLfloat yrot;               
GLfloat zrot;               

GLuint  m_nTexId;           
unsigned char tex;

int h = 1024;           
int w = 256;
int slices = 10;

GLfloat dOrthoSize = 1.0f;

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);   

// EDIT HERE

PFNGLTEXIMAGE3DPROC TexImage3D;
PFNGLTEXSUBIMAGE3DPROC TexSubImage3D;
PFNGLCOPYTEXSUBIMAGE3DPROC CopyTexSubImage3D;

int LoadGLTextures()    
{
    glGenTextures(1,(GLuint*)&m_nTexId );

    if(m_nTexId == 0)
    return false;

    glBindTexture( GL_TEXTURE_3D, m_nTexId );
    glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
    glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
    glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
    glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_BORDER);
    glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    return true;
}


GLvoid ReSizeGLScene(GLsizei width, GLsizei height)     
{
    if (height==0)                                      
    {
        height=1;
    }

    glViewport(0,0,width,height);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();   
}

int InitGL(GLvoid)  
{
    if (!LoadGLTextures())
    {
        return FALSE;
    }

    glEnable(GL_TEXTURE_3D);
    glShadeModel(GL_SMOOTH);
    glClearColor(0.0f, 0.0f, 0.0f, 0.5f);   
    glClearDepth(1.0f);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL); 
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);

// EDIT HERE

    TexImage3D = (PFNGLTEXIMAGE3DPROC) wglGetProcAddress("glTexImage3D");
    TexSubImage3D = (PFNGLTEXSUBIMAGE3DPROC) wglGetProcAddress("glTexSubImage3D");
    CopyTexSubImage3D = (PFNGLCOPYTEXSUBIMAGE3DPROC) wglGetProcAddress("glCopyTexSubImage3D");

    return TRUE;
}

#define MAP_3DTEXT( TexIndex ) \
    glTexCoord3f(0.0f, 0.0f, ((float)TexIndex+1.0f)/2.0f);  \
    glVertex3f(-dOrthoSize,-dOrthoSize,TexIndex);\
    glTexCoord3f(1.0f, 0.0f, ((float)TexIndex+1.0f)/2.0f);  \
    glVertex3f(dOrthoSize,-dOrthoSize,TexIndex);\
    glTexCoord3f(1.0f, 1.0f, ((float)TexIndex+1.0f)/2.0f);  \
    glVertex3f(dOrthoSize,dOrthoSize,TexIndex);\
    glTexCoord3f(0.0f, 1.0f, ((float)TexIndex+1.0f)/2.0f);  \
    glVertex3f(-dOrthoSize,dOrthoSize,TexIndex);


int DrawGLScene(GLvoid)
{
    PFNGLTEXIMAGE3DPROC glTexImage3D = (PFNGLTEXIMAGE3DPROC) wglGetProcAddress("glTexImage3D");
    PFNGLTEXSUBIMAGE3DPROC glTexSubImage3D = (PFNGLTEXSUBIMAGE3DPROC) wglGetProcAddress("glTexSubImage3D");
    PFNGLCOPYTEXSUBIMAGE3DPROC glCopyTexSubImage3D = (PFNGLCOPYTEXSUBIMAGE3DPROC) wglGetProcAddress("glCopyTexSubImage3D");

    glClear( GL_COLOR_BUFFER_BIT  | GL_DEPTH_BUFFER_BIT );

    //glEnable( GL_ALPHA_TEST );
    //glAlphaFunc( GL_GREATER, 0.2f );

    //glEnable(GL_BLEND);
    //glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );

    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity();
    gluLookAt(0,0,-300,0,0,1,0,1,0);


    glEnable(GL_TEXTURE_3D);
    glBindTexture( GL_TEXTURE_3D,  m_nTexId );

    TexImage3D(GL_TEXTURE_3D, 0, GL_RGBA, w, h , slices, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL );


    glTranslatef( 0.0f, 0.0f, 100.0f );


    glBegin(GL_QUADS);
    tex = (unsigned char)SOIL_load_image("Data/PA_170090.png", &w, &h, NULL, 0);
    TexSubImage3D(GL_TEXTURE_3D, 0, 0, 0, 1, w, h, 1, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*) tex);
    MAP_3DTEXT( 0.0f );
    glEnd();

    glBegin(GL_QUADS);
    tex = (unsigned char) SOIL_load_image("Data/PA_170091.png", &w, &h, NULL, 0);
    TexSubImage3D(GL_TEXTURE_3D, 0, 0, 0, 2, w, h, 1, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*) tex);
    MAP_3DTEXT( 0.1f );
    glEnd();

    glBegin(GL_QUADS);
    tex = (unsigned char)SOIL_load_image("Data/PA_170092.png", &w, &h, NULL, 0);
    TexSubImage3D(GL_TEXTURE_3D, 0, 0, 0, 3, w, h, 1, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*) tex);
    MAP_3DTEXT( 0.2f );
    glEnd();

    glBegin(GL_QUADS);
    tex = (unsigned char)SOIL_load_image("Data/PA_170093.png", &w, &h, NULL, 0);
    TexSubImage3D(GL_TEXTURE_3D, 0, 0, 0, 4, w, h, 1, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*) tex);
    MAP_3DTEXT( 0.3f );
    glEnd();

    glBegin(GL_QUADS);
    tex = (unsigned char)SOIL_load_image("Data/PA_170094.png", &w, &h, NULL, 0);
    TexSubImage3D(GL_TEXTURE_3D, 0, 0, 0, 5, w, h, 1, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*) tex);
    MAP_3DTEXT( 0.4f );
    glEnd();

    glBegin(GL_QUADS);
    tex = (unsigned char)SOIL_load_image("Data/PA_170095.png", &w, &h, NULL, 0);
    TexSubImage3D(GL_TEXTURE_3D, 0, 0, 0, 6, w, h, 1, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*) tex);
    MAP_3DTEXT( 0.5f );
    glEnd();

    glBegin(GL_QUADS);
    tex = (unsigned char) SOIL_load_image("Data/PA_170096.png", &w, &h, NULL, 0);
    TexSubImage3D(GL_TEXTURE_3D, 0, 0, 0, 7, w, h, 1, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*) tex);
    MAP_3DTEXT( 0.6f );
    glEnd();

    glBegin(GL_QUADS);
    tex = (unsigned char) SOIL_load_image("Data/PA_170097.png", &w, &h, NULL, 0);
    TexSubImage3D(GL_TEXTURE_3D, 0, 0, 0, 8, w, h, 1, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*) tex);
    MAP_3DTEXT( 0.7f );
    glEnd();

    glBegin(GL_QUADS);
    tex = (unsigned char) SOIL_load_image("Data/PA_170098.png", &w, &h, NULL, 0);
    TexSubImage3D(GL_TEXTURE_3D, 0, 0, 0, 9, w, h, 1, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*) tex);
    MAP_3DTEXT( 0.8f );
    glEnd();

    glBegin(GL_QUADS);
    tex = (unsigned char) SOIL_load_image("Data/PA_170099.png", &w, &h, NULL, 0);
    TexSubImage3D(GL_TEXTURE_3D, 0, 0, 0, 10, w, h, 1, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*) tex);
    MAP_3DTEXT( 0.9f );
    glEnd();

    return TRUE;

}

【问题讨论】：

您应该在DrawGLScene 函数之外的范围内声明您的glTexImage3D 等函数指针，然后在您调用InitGL (...) 时加载这些指针。每次绘制场景时从驱动程序获取函数指针是没有意义的，它们永远不会改变。同样，您的纹理文件是否每帧都更改？如果不是，您可能只想加载它们一次……您目前对磁盘 I/O 施加了很大压力。
但最重要的是，我不明白您为什么要转换纹理矩阵？您已经在 MAP_3DTEXT(...) 宏中为切片提供了 Z 坐标。您可能应该改用 ModelView。
@AndonM.Coleman 是的，当我尝试模拟实时系统时，我的帧每秒都在变化。因此，我需要硬件一直在重新加载图像。请参阅我在代码中的编辑，即在全局范围内声明 PFNGLTEXIMAGE3DPROC 和相关指针，并在 InitGL() 中定义指针。
每一秒都不同于每一帧。您应该定期（每 1 秒）重新加载纹理，并在过渡期间重新使用加载的图像切片。此外，您的编辑并没有太大变化。您正在隐藏DrawGLScene (...) 中的同名变量。
@AndonM.Coleman 对，再次编辑。稍后我将修改代码以与系统一起工作，但现在我想坚持这个例子，看看为什么它仍然不起作用。我对 3D 纹理映射的了解仍在不断发展。你能告诉我应该如何转换 ModelView 吗？

标签： opengl

【解决方案1】：

查看函数调用 TexSubImage3D，参数深度始终为 1，并且您仅递增 zoffset。请保持 zoffset 为 0 并提供来自第 8 个参数（深度）的深度/层值。

TexSubImage3D( enum target, int level, int xoffset, int yoffset, int zoffset, sizei width, sizei height, sizei depth, enum format, enum type, const void *data );

【讨论】：