[Paraview] Emissive polygons?

[Moreland, Kenneth]

No, they are different (although you might be able to get a similar effect).  The ambient light represents a base level of lighting coming from all directions that is formed (in real life) by light coming actual light sources and bouncing around the objects in the room.  It is the light that illuminates an object that is in shadow from all light sources.  Because OpenGL does not compute the amount of light that gets scattered around the scene, for each light you specify an ambient parameter representing the amount you expect the light to be bouncing around the scene.  OpenGL also allows you to specify different colors for ambient and diffuse reflection of materials.  In real life, these are always the same, but changing them sometimes allows you to work around some of the approximations that OpenGL makes.

Emission is light that originates directly from an object.  It is a color that is completely impendent of any lights (because the light is coming from the object itself).  Objects like turned on light bulbs or glow-in-the-dark toys have emission.  Unlike in real life, light from polygons with emission in OpenGL do not affect other objects (another approximation introduced by OpenGL).

For more information, check out the chapter on Lighting in the red OpenGL book.

-Ken


On 2/19/09 7:45 AM, "Berk Geveci" <berk.geveci at kitware.com> wrote:

I am probably confused here but isn't setting ambient to larger than 0
in vtkProperty supposed to do that?

-berk

On Wed, Feb 18, 2009 at 4:23 PM, Moreland, Kenneth <kmorel at sandia.gov> wrote:
> I'm afraid not.  It looks like that functionality is not even support in
> VTK.  Implementing light emission that is constant for whole objects would
> be pretty straightforward, but would require modifying code all the way to
> VTK's rendering layer.
>
> -Ken
>
>
> On 2/18/09 1:55 PM, "Eric E. Monson" <emonson at cs.duke.edu> wrote:
>
> Hello,
>
> I'm not sure if I'm using the proper terminology, but is it possible
> in ParaView to give polygons or 3d cells an "emissive" property for
> the lighting, so they "give off" light instead of reflecting it?
>
> Thanks,
> -Eric
>
> ------------------------------------------------------
> Eric E Monson
> Duke Visualization Technology Group
>
>
>
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>    ****      Kenneth Moreland
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   ****      Kenneth Moreland
    ***      Sandia National Laboratories
***********
*** *** ***  email: kmorel at sandia.gov
**  ***  **  phone: (505) 844-8919
    ***      web:   http://www.cs.unm.edu/~kmorel

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