Dreamcast-Talk.com

Gary_b wrote:explain how to calculate the polygons and i will try to test it. i got the game running on my PC. it runs like shit but it does work. if i have to set shit up in NullDC tell me what needs to be done.

sin wrote: I will try to upload a screenshot sometime so you can check it out, and i really hope to find some free time so i can work on my new format and check out the dc's limits.

sin wrote:regarding polygon counts...if you want decent image quality you need an 640x480x24bpp resolution which leaves us with roughly 6 megabytes for geometry and textures. Assuming you use all 6 of them for geometry (clearly not realistic), you end up with 3 megabytes for each of the 2 vertex buffers that reside in vram. The simplest useful vertex format for the powervr chipset needs 32 bytes per vertex, so we can afford roughly 90000 vertices because some space is also consumed for tile organization etc...so do the math....that's 30000 triangles. If you manage to transform and light them at 60 fps, you got 1.8 million triangles. That's about it, end of story, the vram can't hold more at this level of image quality. If you want more you need to lower the resolution or bits per pixel, or work with stripped frame buffers which consume almost no vram space but are very inefficient as far as render time is concerned and a bitch to get working properly. Naomi has double the amount of vram, so it can afford more polys

However, if you manage to organize triangles in triangle strips you can aford much greater "effective" polygon counts. I can easily take a 50000 triangle model that would need 150k vertices in vram and strip it down to 70k vertices with ZERO quality loss. So that gives me an "effective" mesh of 50k triangles, despite the fact that i store it in vram in a very efficient way. With one dynamic point light and one base texture i can do this in full 60 fps, getting an effective 3mpps. From what i have seen no dreamcast game comes close, but of course they need vram space for textures and have also game logic to execute. The highest poly counts i have seen are in DOA2, usually around 10k polygons for characters and backgrounds which is very good considering the quality of lighting and animation of the skinned characters. Lemans has a high poly car in the car selection screen, but in game it uses lower quality models, especially for distant cars. Nowhere near even DOA2's poly counts, but it still looks really nice, one of my favourites. Another good one is ecco, really phenomenal when it came out, i was truly amazed. Also nullDC's author once told me that the emulator sends roughly 25% more geometry because of the way it organizes data, so the numbers you see there are slightly higher than the real ones.

I would like to note that my results evaluate the shader for every vertex sent to the powervr. This is a limitation of my current format, and currently the sh4 maxes out at 80k vertices (almost 160k "effective" vertices) per frame at 60fps, that's 3+ times the amount of geometry of DOA2, and if we look at the "effective" numbers, well make it 6+. Of course i do not do the type of detailed animation they did, but it gives you an idea of the raw amount of geometry the dc can push. I have a new format in the works that will use indexed vertex arrays and will be way faster. This will make transformations and lighting for the sh4 much cheaper, but of course triangle counts can't go up since there is the vram space limitation. I will try to upload a screenshot sometime so you can check it out, and i really hope to find some free time so i can work on my new format and check out the dc's limits.

I hope i cleared some things up for you.