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Index > Windows > troubles with big OGL bitmap

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Zetus



Joined: 03 Jun 2004
Posts: 37
Zetus
Hello all,
my program draws an entire screen bitmap with openGL :

invoke glDrawPixels,[ScreenX],[ScreenY],GL_RGB,GL_UNSIGNED_BYTE,[VBuffer2]
xor eax,eax
invoke SwapBuffers,[hdc]

all is good, but only on nVidia chipsets - GeForce, Riva etc
on Intel or ATI cards all works but VERY slow... all of this cards have good OpenGl. What's wrong?

the init procedure for window is mostly regular...
Post 22 Aug 2006, 08:10
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Madis731



Joined: 25 Sep 2003
Posts: 2140
Location: Estonia
Madis731
Check if you have...hmm what was it...that straight connection between RAM <=and=> VIDEO. Maybe if it isn't using/supporting it, then the data always goes through the CPU and you might find a bottle-neck from there.

Maybe they don't have some CAPS and just switch to SW mode and again
it uses your CPU and you might find a bottleneck there.

Anyway - check CPU%usage...

PS. I found this on AnandTech:

Can you spare a DiME?

One of the major advantages of AGP over PCI is its ability to support Direct Memory Execute of textures, otherwise known as DIME. Whenever you draw pixels in a 3D arena, you have two options, they are either (1) texture-mapped or (2) drawn using shading. When you are drawing pixels using the latter option, you don't have to worry about calling or fetching bitmaps to physically draw the pixel. However, when using texture mapped pixels you quickly become aware of the bottlenecks of the standard PCI graphics subsystem. Because of DIME, AGP accelerators (not all, see The Real Benefits of AGP) can use and manipulate your system RAM directly whenever the need for intense texture-mapping functions are in demand.

I recall it was AGP Aperture, but this had something to do with video-card
stealing RAM or sth...
Post 22 Aug 2006, 11:47
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SomeoneNew



Joined: 12 Aug 2006
Posts: 54
SomeoneNew
Zetus is your image size a power of 2 ? on new cards its possible that the drivers might be converting your image to a power of 2 every time you set it to opengl...

Many things could be slowing down your rendering, I should see your initialization code and the image specs at least.
Post 22 Aug 2006, 18:23
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Zetus



Joined: 03 Jun 2004
Posts: 37
Zetus
Thanks anyway)

i'll found:

DirectDraw based out has normal speed, on all cards
power of 2 sizing has no effect

it seems need to change out temporary to bitblt or somthing same...
Post 23 Aug 2006, 06:17
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