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Coleco

Is my math right??

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I am doing a textured-quad based 2D game in D3D9. I am wondering how far I can push my video card. Anyway, my card at home is a Radeon 7500. According to ATI, it can display 500 Mpixel/sec. Now, in past experiences, I have found that "maximum limits" rarely occur in real life. So, assuming best case is half that (250 Mpixel/sec), I was wonding if the following would be true: Practical number of pixels per second: 250,000,000 Target FPS: 60 Number of pixels in 1/60th second: 4,166,666 64x64 pixel sprites = 4096 pixels Number of 64x64 pixel sprites in 1/60 sec: 1,017 (Numbers are rounded) My current engine is getting 2048 sprites at 27 fps....which seems pretty close...which should be 226,492,416 pixels per second. Damn...sure seems like I am approaching that "practical maximum limit" lol....And my engine is NOT optimized. I am doing a LOCK/Draw Primitive on EVERY SPRITE (don''t laugh...I am a 3D newbie). So, if ATI was correct, shouldn''t I be able to get about 4000 sprites at 27 FPS or that same 2000 at about 60 FPS? Thanks! -cbmeeks

~ c o l ec o ~

Rock the cradle of love! You stupid WANKER! S i g n a l D E V .com Metroid Classic

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Might be possible if your program that does all the drawing consumes zero CPU and cost no other overhead at all. It''s fine with theoretical numbers but for a normal 2d game you will not get close to using all that you need anyway.

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Oh yeah, I realize that. I guess what I am going for is I am wondering how many sprites/tiles I can get practically?

Just seems like I should be able to get enough textured quads for a 640x480 game, 4 layers of parallax scrolling, and maybe 100 sprites on sceen. Does that seem possible even on a low-end 3D card? I know 2D DirectDraw can do that.

-cbmeeks

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I did a similar test on my own particle system to see if fillrate was my issue, however with a GeForce3. I search on the net for fillrate values, and found 3 or 4 conflicting values. nVidia claimed one thing, but with a footnote saying it''s only valid when using Quincunx AA. I decided to use the lowest value that any site claimed, assuming it''s the "real" value without being in a special mode. When using that number, I was pretty close... within a few percent.

Their posted fillrate limit may not be achievable when using textures. You may hit a memory bandwidth limit. Their fillrate limit may not be achievable when Z is enabled... it requires memory. On the latest nVidia cards the fillrate doubles when Z is disabled, and on the latest ATi cards the fillrate doubles when AA is enabled.

You''ve got to be careful when interpreting these numbers. As long as it''s acting like you''ve hit the memory bandwidth/fillrate limit, regardless of what the numbers may say, you already know what the issue is.

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