copy GL_TEXTURE_2D into one slice of a GL_TEXTURE_2D_ARRAY Texture

Question

I'm trying to copy one GL_TEXTURE_2D into a chosen slice of a GL_TEXTURE_2D_ARRAY Texture.

I try to bind the usual Texture_2D to one framebuffer and only a slice of the Texture_2D_Array to another framebuffer (both have the same size (width, height, GL_RGB, GL_UNSIGNED_BYTE)). Afterwards I thought to glBlitFramebuffer would copy that texture into this one slice... but I think I misunderstand the glFramebufferTexture3D command.

BTW: the GL_TEXTURE_2D is loaded correctly and I also printed it out (works)

Here my code:

//Create 2 FBOs for copying textures
glGenFramebuffers(1, &nFrameBufferRead); //FBO for texture2D
glGenFramebuffers(1, &nFrameBufferWrite); //FBO for one slice of the texture2d_array
CBasics::GetOpenGLError(); 

//generate the GL_TEXTURE_2D_ARRAY with given values (glgentextures is already called for this texture)
glTexImage3D(GL_TEXTURE_2D_ARRAY, 0, GL_RGB, nWidth, nHeight, countSlices, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL);
CBasics::GetOpenGLError();  

//Bind the Texture2D to the readFramebuffer
glBindFramebuffer(GL_READ_FRAMEBUFFER, nFrameBufferRead);
glFramebufferTexture(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, texture2D_ID, 0);
CBasics::GetOpenGLError();

//try to bind the Texture2D_Array to the drawFramebuffer
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, nFrameBufferWrite);
CBasics::GetOpenGLError(); //till here everything works (no glerror)
glFramebufferTexture3D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D_ARRAY, texture2D_Array_ID, 0, slicenumber); // here the error appears 
CBasics::GetOpenGLError();

//because of the error one step earlier here will be the next error... 
glBlitFramebuffer(0, 0, nWidth, nHeight, 0, 0, nWidth, nHeight, GL_COLOR_BUFFER_BIT, GL_NEAREST);
CBasics::GetOpenGLError();

at glFramebufferTexture3D the error appears: GL_INVALID_VALUE I think it is because of

GL_INVALID_VALUE is generated if texture is not zero or the name of an existing texture object.

1st: Is this way to copy textures into arrayslices correctly? Or is there a better way to do that?

2nd: Is it possible to bind only one slice of a GL_TEXTURE_2D_ARRAY?

3rd: Do I need the glFramebufferTexture3D command or the glFramebufferTexture2D command for GL_TEXTURE_2D_ARRAYs?

Are you actually trying to copy the data, or do you want to render to that array layer? Because these are two very different operations. — Nicol Bolas
@NicolBolas I am trying to copy the data... after this method inside the TEXTURE_2D_ARRAY the one slice should be the TEXTURE_2D — Thomas

Nicol Bolas Nicol Bolas · Accepted Answer · 2017-09-20T21:05:31

Assuming that "Here's my code" actually does contain all of your code, it doesn't work because you didn't bind the 2D array texture before calling glTexImage3D to allocate storage for it.

However, you don't have to render or blit to copy texture data. You can copy texture data by... copying texture data. The glCopyImageSubData function can copy layers between textures with different array layer counts. In your case:

glCopyImageSubData(
    texture2D_ID, GL_TEXTURE_2D, 0, 0, 0, 0,
    texture2D_Array_ID, GL_TEXTURE_2D_ARRAY, 0, 0, 0, slicenumber,
    nWidth, nHeight, 1);

This requires OpenGL 4.3 or better, or one of the ARB/NV_copy_image extensions. The NVIDIA extension is actually quite widely implemented.

But you still need to use glTexImage3D correctly.

copy GL_TEXTURE_2D into one slice of a GL_TEXTURE_2D_ARRAY Texture

1 Answers