将2D图像映射到3D纹理

Question

Question: I am trying to map a single 2D image to a 3D texture. When I visualize the output, OpenGL renders a white texture floating in black background. Why is this happening? Is it possible to map a 2D image to a 3D texture?

My goal is to place multiple 2D images along the z-dimension to resemble a volume. An example of such an approach is in this video: http://cvlab.epfl.ch/research/medical/em/synapses

Approaches attempted: I took 2D images and mapped them to 2D textures. I have also used 2D texture arrays. Both of these approaches provide a good result. However, when I tried to paint the surface of a 3D texture with the same image, I get a white texture floating around in a black space.

Code I have followed the texture mapping tutorial that is available on NeHe's website. http://nehe.gamedev.net/tutorial/lesson_06_texturing_update/47002/

Except changes to these three functions, everything else in the program (present in the solution file in the website) is the same.

... // header file declarations

#include <glext.h>

PFNGLTEXIMAGE3DPROC glTexImage3D;
GLuint  texture;    


int LoadGLTextures()    // Load Bitmaps And Convert To Textures
{
            /* load an image file directly as a new OpenGL texture */

            texture = SOIL_load_OGL_texture("Data/NeHe.bmp",SOIL_LOAD_AUTO, 
            SOIL_CREATE_NEW_ID,S OIL_FLAG_INVERT_Y);
            // "Data/NeHe.bmp"

            if(texture == 0) {return false;}

            glTexImage3D = (PFNGLTEXIMAGE3DPROC) wglGetProcAddress("glTexImage3D");
            if (glTexImage3D == NULL) 
            {
            printf("Error in line %d: Couldn't load glTexImage3D function. Aborting.\n", __LINE__);
            return -1;
            }

    glBindTexture(GL_TEXTURE_3D, texture);
    glTexParameteri(GL_TEXTURE_3D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
    glTexParameteri(GL_TEXTURE_3D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
    //glTexImage3D(GL_TEXTURE_3D, 0, GL_RGBA, 4096, 4096, 1, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
    return true;    
}


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

    glEnable(GL_TEXTURE_3D);
    // glEnable(GL_TEXTURE_2D); 
    glShadeModel(GL_SMOOTH);    //
    glClearColor(0.0f, 0.0f, 0.0f, 0.5f);   // Black Background
    glClearDepth(1.0f);         // Depth Buffer Setup
    glEnable(GL_DEPTH_TEST);    
    glDepthFunc(GL_LEQUAL);     
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST); // Really Nice Perspective calculations
    return TRUE;    // Initialization Went OK
}


int DrawGLScene(GLvoid)   
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
    glLoadIdentity();   
    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]);
    glBindTexture(GL_TEXTURE_3D, texture);
    glBegin(GL_QUADS);

    glTexCoord3f(0.0f, 0.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  0.0f);
    glTexCoord3f(1.0f, 0.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  0.0f);
    glTexCoord3f(1.0f, 1.0f, 0.0f); glVertex3f( 1.0f,  1.0f,  0.0f);
    glTexCoord3f(0.0f, 1.0f, 0.0f); glVertex3f(-1.0f,  1.0f,  0.0f);

    glEnd();

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

...

Answer 1

It is better to use 3D textures instead of 2D ones as you will be able to apply rotations correctly using glRotate(). You will also need to do blending and/or alpha-testing to see different layers of your 2D image.

To create a 3D texture, you can create an array of dimension [width x height x number_of_slices] and then store the raw data slice by slice

Look at this tutorial: http://www.codeproject.com/Articles/352270/Getting-started-with-Volume-Rendering?msg=4729498#xx4729498xx

It's very good and it worked for me to do the same thing