Question

Can anybody help with converting an SDL_Surface object, a texture loaded from a file, into an IDirect3DTexture9 object.

Answer 1

I honestly don’t know why you would ever want to do this. It sounds like a truly horrible idea for a variety of reasons, so please tell us why you want to do this so we can convince you not to ;).

In the meanwhile, a quick overview of how you’d go about it:

IDirect3DTexture9* pTex = NULL;
HRESULT            hr   = S_OK;
hr = m_d3dDevice->CreateTexture(
    surface->w,
    surface->h,
    1,
    usage,
    format,
    D3DPOOL_MANAGED,
    &pTex,
    NULL);

This creates the actual texture with the size and format of the SDL_Surface. You’ll have to fill in the usage on your own, depending on how you want to use it (see D3DUSAGE). You’ll also have to figure out the format on your own – you can’t directly map a SDL_PixelFormat to a D3DFORMAT. This won’t be easy, unless you know exactly what pixel format your SDL_Surface is.

Now, you need to write the data into the texture. You can’t use straight memcpy here, since the SDL_Surface and the actual texture may have different strides. Here’s some untested code that may do this for you:

HRESULT        hr;
D3DLOCKED_RECT lockedRect;

// lock the texture, so that we can write into it
// Note: if you used D3DUSAGE_DYNAMIC above, you should 
// use D3DLOCK_DISCARD as the flags parameter instead of 0.
hr = pTex->LockRect(0, &lockedRect, NULL, 0);
if(SUCCEEDED(hr))
{
    // use char pointers here for byte indexing
    char*  src     = (char*) surface->pixels;
    char*  dst     = (char*) lockedRect->pBits;
    size_t numRows = surface->h;
    size_t rowSize = surface->w * surface->format->BytesPerPixel;

    // for each row...
    while(numRows--)
    {
        // copy the row
        memcpy(dst, src, rowSize);

        // use the given pitch parameters to advance to the next
        // row (since these may not equal rowSize)
        src += surface->pitch;
        dst += lockedRect->Pitch;
    }

    // don't forget this, or D3D won't like you ;)
    hr = pTex->UnlockRect(0);
}