Re: Mathematica Lightning Model?
- To: mathgroup at smc.vnet.net
- Subject: [mg14742] Re: Mathematica Lightning Model?
- From: Martin Kraus <mkraus at theorie3.physik.uni-erlangen.de>
- Date: Thu, 12 Nov 1998 02:17:41 -0500
- Organization: Regionales Rechenzentrum Erlangen, Germany
- References: <72bdtl$k11@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Alexander Otte wrote:
>
> Hi!
>
> How can it be, that the shading of an object depends on the distance
> between object and viewer?
>
> The following line of code shows the problem:
>
> Plot3D[Sin[x] Cos[y],{x,0,2 Pi},{y,0,2 Pi},
>
> LightSources->{{{1,0,1},RGBColor[1,0,0]}},ViewPoint->1000{1.3,-2.4,2.0}]
>
> The surface is rendered with a single color. Even if an object is far
> away - should't the intensity of diffuse reflected light depend on the
> angle between the surface normals and the direction of light?
>
> So what kind of lightning model (lightning equation) does Mathematica
> use?
>
> Thanks
>
> Alex
Hi,
as far as I understand, the problem is that the ViewPoint vector is not
properly normalized in the calculation of shadings. For long ViewPoint
vectors this leads to a squeezing of the graphics in the direction of
the ViewPoint vector with respect to the lightning. Therefore, the
graphics in your case are shaded as if they were flat; thus, they are
uniformly colored.
This is a known bug. Hopefully it will be corrected somewhen.
Greetings
Martin Kraus