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PowerVR Series2


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#1 Alastair   Members   -  Reputation: 122

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Posted 02 January 2000 - 03:10 AM

I noticed that there''s a new PowerVR chipset. Its used in the latest VideoLogic card - the Neon250. I have read on the VideoLogic web site that the PowerVR does not use a conventional z-buffer for hidden surface removal. Can anyone confirm or deny this? What does it do? How do I get it to render my triangles in the right order under DX7? So many questions but I can''t find one to play with :)

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#2 mhkrause   Members   -  Reputation: 122

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Posted 02 January 2000 - 10:02 AM

PowerVR 1 & 2 do not have Z-Buffers. You can tell this because they expose the ZBUFFERLESSHSR flag in D3D.

Most cards are "immediate." You send a triangle to the card with DrawPrim and it is immediately (or almost immediately) drawn to the screen. PowerVR''s are "scene capture" cards. No rendering is done between BeginScene() and EndScene() pairs. When the scene is ended, all triangles are rendered. This is done by splitting the screen up into tiles, and casting a ray for each pixel and seeing which triangle it intersects.

This has a couple advantages. There is no need for a Z-Buffer, so you can save some VRAM, and you get order-independent alpha blending.

BTW, PowerVR 2 is used in Sega''s Dreamcast console.




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