Copy buffer

Blitz3D Forums/Blitz3D Programming/Copy buffer

licin

(Posted 2009) [#1]

Hi,

Is there a way to copy blitz backbuffer memory
to another application memory?

Warner

(Posted 2009) [#2]

Sure, but it is not easy. The most straightforward method is saving the backbuffer onto disk, and then loading it from the other application.
Else, you could maybe create a stream (tcpstream?) and transfer the data via that.. I never tried that.
More direct acces would be finding the D3DDevice of the blitz app, and pass it to the other application.
Direct3DDevice7=SystemProperty$("Direct3DDevice7")

However, this is not easy, and it has been long since I tried something like that. I was able to access the backbuffer from a .DLL
As I remember it, reading from it was quite fast, but writing to it was slow. I only have a small piece of the code for that, written in Delphi.

//this function copies the z-buffer to the rendertarget
procedure LockZBuffer(lpDevice : IDirect3DDevice7); stdcall;
var
   surf2, surf : IDirectDrawSurface7;
   caps : TDDSCaps2;
begin
  //get rendertarget
  lpDevice.GetRenderTarget(surf);
  surf.GetCaps(caps);
  caps.dwCaps := DDSCAPS_ZBUFFER;
  //get z-buffer
  surf.GetAttachedSurface(caps, surf2);
  //copy z-buffer to rendertarget
  surf.BltFast(0, 0, surf2, rect(0,0,799,599), 0);
  //clear z-buffer
  lpDevice.Clear(1, r, D3DCLEAR_ZBUFFER, $000000, 0, 0);
end;

Where 'Rendertarget' is the backbuffer.

licin

(Posted 2009) [#3]

hmm...

When I call the command "backBuffer()" it is suposed
to return a memory area where the buffer pixels are stored,
right ?

Or it returns a memory area that only Blitz "knows to read" ?

Gabriel

(Posted 2009) [#4]

When I call the command "backBuffer()" it is suposed
to return a memory area where the buffer pixels are stored,
right ?

No, I don't think it is right. As I understand it the BackBuffer (or FrameBuffer as it may also be called) is stored in videoram, and it is not possible to read videoram. This is nothing to do with Blitz3D, or how it reads things, it's simply the way that videocards work. In order to have direct access to a framebuffer, you have to make a copy of it in system memory, which I think is what Warner does above, and it's not terribly fast to copy big chunks of memory around like that.

Bobysait

(Posted 2009) [#5]

As I remember, You can get the D3DS7 surface using :
PeekMemInt(BackBuffer()+12)

but If it's for a copy, maybe it could be easier to use the clipboard to store data to share...