Thought I'd start a new topic on this one. I'm having an issue rendering my screen layers.

My first layer, the game scene, is rendered to the back buffer, my next scene, the HUD (which currently is just a bunch of text quads), is rendered to a render target. I then blend the HUD render target onto the back buffer with a very simple full screen quad shader.

The problem is that my HUD render target doesn't appear to be fully transparent in the areas where I haven't drawn text. When I Clear the render target I clear it with 0,0,0,0 which I thought would give me a fully transparent surface. I then render my text quads to that target.

When I blend, the HUD layer just appears to cover the back buffer surface completely. If I adjust the alpha component in the output of the simple blend pixel shader to something like 0.5 then I get half brightness on the background and half brightness on the HUD layer.

Is there some special blend mode parameters I need to set for rendering alpha to rendertargets?

My blending is:

BlendOp=ADD;
SrcBlend=SRCALPHA;
DestBlend=INVSRCALPHA;
AlphaBlendEnable=TRUE;

This shader is very simple, renders to the back buffer and just takes a sample from the HUD layer.

The HUD only has a couple of lines of text, the rest of the area (which is 99% of it) should be transparent but is coming through as opaque.

If I manually set the alpha in the blend shader pixel shader return value to 0.5 it works, but obviously the areas of the HUD that haven't been drawn on should be alpha 0.

I saved the texture from pix (dds) and the opacity was 255 (full)...

Yes, just a very simple tex2d

Texture format for the render target is A8R8G8B8.

So I guess it means my clear is not clearing it to transparent...?

Are you clearing with D3DCOLOR_ARGB(0,0,0,0)?

Even D3DCOLOR_XRGB(0,0,0) should do (no warranty), just make sure its three zeros and not like 255.

Betting it's clear color too.

Should I not be clearing colour?

Are you clearing with D3DCOLOR_ARGB(0,0,0,0)?

Even D3DCOLOR_XRGB(0,0,0) should do (no warranty), just make sure its three zeros and not like 255.

Yes, definitely clearing with 4 zeros. I can't quite remember whether it's XRGB or ARGB (I'll check) but it's definitely 4 zeros.

Thats what my clear call is looking like:

m_lpDevice->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_ARGB(0,0,0,0), 1.0f, 0);

What does yours look like? Did you make sure the texture is still bound to the device when clearing? Does this happen in release and debug mode? I remember having a very similar issue with alpha transparency, only in release mode, I try to find the thread (it's quite old), can't recall the solution anymore...