On Sunday 26 Jun 2005 21:53, Frederic Bouvier wrote:
> Vivian Meazza a écrit :
> >I've just seen the new volumetric shadows. Brilliant!!! On a
> > Nvidia gForce 5200, the frame rate hit is about 10 in
> > external view (I can live with it) and no noticeable effect
> > in internal - perhaps 1 or 2.
> Yes, it is very nice. I have a drop of 10 fps ( 50 -> 40 )
> when I enable all ( ac + ai + to )
> >There's a bit of a funny with the interaction between the
> > Hurricane propeller disk and the ac shadow: it makes the
> > shadow disappear, and there's something throwing a shadow on
> > to the disk, which I've not seen in real life, although I
> > might not have noticed it. Is there anything I can do within
> > the ac model to tidy this up?
> 2 stranges things that I know are inherent to the shadow
> volume technique : 1. even when surfaces are smoothed, the
> shadows are hard and apply to a whole quad when a fuselage
> shadows itself ( try the A320, look at the airframe and press
> t to see what I mean ).
> 2. transparent surfaces ( the suspension chains of the
> bridges, or the metallic structures ) produce filled shadows.
> Let wait the hardware to catch up a hit, and we could have
> clouds and mountains casting shadows ;-)
> Good job again.
> -Fred

Yes, very nice work.  I notice a little frame-rate drop but not 
as much as I expected (nVidia 6600 based card).

I noticed problems with prop disks too.  I'm fading both the 
props and prop disks in and out, depending on their rpm and even 
when the prop disk is completely faded out a shadow from the 
spinners is cast on them.  As the disks are faded in the shadow 
density upon the prop disk seems to remain constant.

I imagine that varying the shadow density based on the alpha 
channel of the texture of the object that the shadow is cast 
upon would not be trivial.

I also noticed that the props, before being faded out, also cast 
a shadow upon the still faded out prop disks but don't once 
they're de-selected.

I noticed a few 'artifacts' in the shadows cast upon the aircraft 
itself but I think most of these were due to tiny irregularities 
in the model geometry that are normally not noticed due to 
smoothing i.e. tiny concavities in the model which may not be 
obvious but which cast shadows.  The shadow of the tailfin 
moving across the tailplanes is fine though, as was the shadow 
of the wing trailing edge upon the partially deployed flaps.

I don't think I've seen the problem Fred reported of entire quads 
being shadowed incorrectly  (hmm - Fred, are you referring to 
four-sided polys here?  Any polys with > 3 sides appear to be 
triangulated before rendering.


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