Re: [Algorithms] VB vs primitives (was Polygon clipping)

[Martin G. <bz...@wi...>]

Can anybody explain me, why rendering untransformed, unlit, single-textured
stripes from a huge optimized wr-only vertex buffer is about 50% slower versus
rendering them from a huge primitive? Is it something related to the software
T&L? We are using ATI Fury 128, DirectX 7 and DrawIndexedPrimitiveVB vs.
DrawIndexedPrimitive. The vertex percent of total vertices per D3D call is
about 0.5%. Any idea?

Thanks in advance,
Martin

P.S. apologies if this is OT


-----Original Message-----
From: Tom Forsyth <to...@mu...>
To: gda...@li...
<gda...@li...>
Date: 26 Þëè 2000 ã. 12:58
Subject: RE: [Algorithms] Polygon clipping


>Fans remain fans (though it may be knarly to find the ordering), strips
>don't - they can become multiple strips (think about a U-shaped strip where
>the bottom of the U is off-screen).
>
>You might also want to try sending objects that intersect the frustum edges
>through the non-VB path, so that D3D clips them for you - it's actually
>pretty fast. Things that don't need clipping should still go through the VB
>path of course.
>
>Oh, and I really recommend indexed lists instead of lots of little strips
>and fans - you get far too many D3D calls that way, and if you're going to
>do your own clipping, indexed lists are very easy to handle.
>
>Tom Forsyth - Muckyfoot bloke.
>Whizzing and pasting and pooting through the day.
>
>> -----Original Message-----
>> From: Klaus Hartmann [mailto:k_h...@os...]
>> Sent: 25 July 2000 23:49
>> To: gda...@li...
>> Subject: [Algorithms] Polygon clipping
>>
>>
>> Hi all,
>>
>> Even though this is not an API-specific question, I'd like to use an
>> API-specific example to explain my problem.
>>
>> In Direct3D, when using *vertex buffer* with pre-transformed
>> and pre-lit
>> vertices, then Direct3D does not perform any clipping. So I
>> have to do this
>> myself. I could probably go ahead an clip single triangles
>> with a Sutherland
>> Hodgman algorithm, but...
>>
>> How do you people clip triangle strips and triangle fans? Is
>> it possible to
>> clip them so, that strips remain strips, and fans remain
>> fans, or is this
>> impossible?
>>
>> Also, which is the prefered clipping algorithm? Is it
>> Sutherland Hodgman?
>>
>> When you answer, please keep in mind that I also need to clip texture
>> coordinates and the diffuse/specular colors.
>>
>> Any help is greatly appreciated,
>> Niki
>>
>>
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>
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