Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
1998
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 1998

[Date Index] [Thread Index] [Author Index]

Search the Archive

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


  • Prev by Date: Re: A "singular" equation
  • Next by Date: Re: Multi-Variate Taylor Series Expansions
  • Previous by thread: Mathematica Lightning Model?
  • Next by thread: Differentiating Piecewise Functions