       Re: Light and surface colors

• To: mathgroup at smc.vnet.net
• Subject: [mg58692] Re: Light and surface colors
• From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
• Date: Fri, 15 Jul 2005 03:02:09 -0400 (EDT)
• Organization: Uni Leipzig
• References: <db57t5\$4vl\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

you have need a half-day for
With[{a = 1, b = 2, c = 1/2},
ParametricPlot3D[
{a*Cos[phi]*Sin[th], b*Sin[phi]*Sin[th],
c*Cos[th], Hue[phi/(2Pi)]},
{th, 0, Pi}, {phi, 0, 2Pi}, Lighting -> False]
]

but wish

With[{a = 1, b = 2, c = 1/2},
ParametricPlot3D[
{a*Cos[phi]*Sin[th], b*Sin[phi]*Sin[th],
c*Cos[th],
SurfaceColor[Hue[phi/(2Pi)]]},
{th, 0, Pi}, {phi, 0, 2Pi}]
]

You can't have shadows in Mathematica. Even when
has no floor or wall to show you the shadow

You can try MathGL3d form

http://phong.informatik.uni-leipzig.de/~kuska/mathgl3dv3/

and save the graphics to POVRay or Renderman and
use these render engines to obtain light sources
with solid walls in the back of the object.

Regards

Jens

schrieb im Newsbeitrag
news:db57t5\$4vl\$1 at smc.vnet.net...
| Hi to everyone.
|
| I've just obtained a Student License of
Mathematica, and I'm working in
| graphics...
|
| I've created, after a half-day of work, an image
representing an ellipsoid,
| with a colored surface
|
| When I try to represent it, I must put
Ligthing->False to see surface
| colors.
|
| I'd like to know if there's a way to obtain a
rendered image, in which I
| can have both light and surface color, to give a
| create a more 3D effect.
|
| Thanks for replies.
|
| Below there's the code...
|
|
| Daniele
|
|
| --------------------------
|
| << Graphics`ContourPlot3D`;
|
| a = 7; b = 5; c = 4; r = 1;
|
| ellipsoid = ContourPlot3D[
|    (x/a)^2 + (y/b)^2 + (z/c)^2 - r, {
|    x, -10, 10}, {y, -10, 10}, {z, -10, 10},
|    PlotPoints -> 12,
|    AspectRatio -> Automatic
|    ];
|
| (*It finds the median point of vertices of a
list of a 3D coordinates*)
| midpoint[l_] := Apply[Plus, Transpose[l],
2]/Length[l];
|
|
| (*Function to map in the ellipsoid surface*)
| pressure[x_, y_, z_] := x^2 + y^2 + Sin[4z];
|
| (*Color Function*)
| color[x_] := Hue[pressure @@ midpoint[x]/50];
|
| (*Rule to change original graphic object*)
| colorpolygon = Polygon[coord_] :>
| {color[coord],EdgeForm[{}],Polygon[coord]};
|
| (*creation of new, colored ellipsoid*)
| coloredellipse = ellipsoid /. colorpolygon;
|
| (*Visualization of the shape*)
| (*I'd like to have also the light...*)
| Show[coloredellipse, Lighting -> False];
|

```

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