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Is there any way to obtain a pointer to the video buffer without using a graphics API like SDL?
I mean if you know where it is could you manually assign a pointer to it? I guess it starts at the same place on every machine?
Something like
Code:unsigned char *video = (unsigned char *) 0x00ABCDEF
Well assuming you can get past the virtual memory protection of your OS,
and can find the physical address where the card video memory is mapped,
and can figure out how that memory is mapped to pixels and screen resolutions,
and ....
What is your question?
I'll be quiet now.
:(
Hang on, so how do OpenGL and SDL get hold of it then? Is there an API call?
i think you would need to do some assembly, but i really have no idea
I'm not sure. Using assembly would surely mean having to use API calls or interrupts.Quote:
Originally Posted by loopshot
Someone must know. I don't need to know, I'm just interested.
In the beginning,
http://computer.howstuffworks.com/pci.htm
You cannot get a pointer to video memory in XP unless you are in the DOS emulator. Even in DJGPP 32-bit you cannot get a pointer to the Linear Frame Buffer or LFB by using a near pointer hack. The near pointer hack works under DOS and Windows 98SE, but not XP.
To obtain a pointer to video memory in 16-bit DOS:
I forget the wait for retrace code but it's still available on the net.Code:
typedef unsigned char BYTE;
BYTE far *pScreen=(BYTE far *)MK_FP(0xA000,0);
BYTE far *Buffer=new BYTE[64000L];
void Flip13h(BYTE far *pScreen,BYTE far *pBuffer)
{
//Wait for vertical retrace.
//....while (!(inp(0x03DA)).... I forget the code sorry
asm {
les di,pScreen
push ds
lds si,pBuffer
mov cx,32000d
rep movsw
pop ds
}
}
You can gain access to the primary buffer and all buffers in Direct3D via the IDirect3DSurface9::Lock() method. I would not make use of this as it will result in degraded performance.