使用图像位图创建多重采样Render Target并从Offscreen-plain复制数据后渲染异常，求排查错误原因

Hey there, I see where the issue is here—let's break this down and fix it!

The core problem is that Direct3D 9's StretchRect doesn't support copying from a non-multisampled surface directly to a multisampled render target. Multisampled surfaces have a completely different memory layout than regular surfaces, so the API blocks this operation (you're probably getting a D3DERR_INVALIDCALL return code here if you check it, which you absolutely should!).

To get your bitmap into a multisampled render target, you need to go through the GPU rendering pipeline instead of trying a direct copy. Here's the step-by-step fix:

1. Add an Intermediate Non-Multisampled Render Target #

First, create a regular (non-multisampled) render target that matches the format/size of your multisampled target. This acts as a bridge between your offscreen bitmap and the multisampled surface.

IDirect3DSurface9* intermediateRT = nullptr;
HRESULT hr = device->CreateRenderTarget(
    width, 
    height, 
    D3DFMT_A8R8G8B8, 
    D3DMULTISAMPLE_NONE,  // No multisampling here
    0, 
    false, 
    &intermediateRT, 
    NULL
);
if (FAILED(hr)) {
    // Handle error (log it, debug, etc.)
}

2. Copy Your Bitmap to the Intermediate RT #

Now you can safely use StretchRect to copy from your offscreen plain surface to this intermediate render target—both are non-multisampled, so this is supported:

hr = device->StretchRect(sourceSurface, NULL, intermediateRT, NULL, D3DTEXF_POINT);
if (FAILED(hr)) {
    // Handle error
}

3. Draw the Intermediate RT to the Multisampled Target #

Use the GPU to render the intermediate surface into your multisampled render target. The easiest way to do this is with ID3DXSprite (a helper for 2D rendering):

First, Initialize the Sprite #

ID3DXSprite* pSprite = nullptr;
hr = D3DXCreateSprite(device, &pSprite);
if (FAILED(hr)) {
    // Handle error
}

Then Render to the Multisampled Target #

// Set the multisampled render target as the active target
device->SetRenderTarget(0, targetSurface);
// Clear the target first (optional but good practice)
device->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0, 0, 0), 1.0f, 0);

// Begin sprite rendering
pSprite->Begin(D3DXSPRITE_ALPHABLEND); // Use ALPHABLEND if your bitmap has transparency

// Get the texture associated with the intermediate render target
IDirect3DTexture9* intermediateTex = nullptr;
intermediateRT->GetContainer(IID_IDirect3DTexture9, (void**)&intermediateTex);

// Draw the texture to fill the entire multisampled render target
pSprite->Draw(intermediateTex, NULL, NULL, NULL, 0xFFFFFFFF);

// End sprite rendering
pSprite->End();

4. Clean Up Resources #

Don't forget to release all the temporary interfaces you created:

SAFE_RELEASE(intermediateTex);
SAFE_RELEASE(pSprite);
SAFE_RELEASE(intermediateRT);

• Always check the return value of every Direct3D API call—this will save you hours of debugging!
• Multisampled surfaces can't be locked directly (via LockRect) or copied to/from non-multisampled surfaces with StretchRect; you must use rendering operations.
• If you don't want to use ID3DXSprite, you can also draw a full-screen quad with the intermediate texture applied—this works too, but Sprite is simpler for 2D blits.

内容的提问来源于stack exchange，提问作者Husker