kike nous apporta ses lumieres en ce 01-03-2007 05:14:
> Hello everybody.
> I'm trying to make the effect of an object burning and falling from the sky
> so it should have a smoke tail (I guess you can imaging what Im talking
> about). I thought I great idea would be to make a mesh with Wings3D and
> then do something like:

> interior{media{absorption 3}}

> probably with density as well. But IT DOESN'T WORK. An here it goes my first
> question DO MESH SUPPORT MEDIA?.

> The second thing is that I know emission and scattering depend strongly on
> the position of both light and camera. Absorption depends as well on the
> relative position of light and camera?

> Thank you


You need to add hollow to the object's deffinition.
If you use the spherical pattern, remember that it's centered at the origin, 
value of 1 at <0,0,0>, droping to 0 at a radius of 1 unit.
If you use the cylindrical pattern, it's centered around the y axis with an 
effective unit radius.
It's beter to create your object at that location and orientation, then to 
rotate and translate to the desired orientation and location.

Emissive media don't interact with your light. It's aspect depent on it's 
colour, it's density and thickness. It don't cast any shadow. Is visible on it's 
own.

Absorbing media will absorb light, will cast shadow and obscure what is behind. 
Aspect is independant on the direction of incident light. It needs something 
behind it to be obscured to be visible.

Scattering media will diffuse light and obscure what is behind it. The 
directionality depends on the scatering model used. Type 1 is isotropic or 
spherical scatering. It's mostly independent of the light's direction relative 
to the camera, it will show some darkening gradient if thick enough in the 
direction of the incoming light.
Type 2 and 3 are strongly directionals. Low effect if the light is behind the 
camera, maximum if you look at the light.
Type 4 have some directionality. Maximum effec if the light is behind or 
directly in front of the camera, less but notable if perpendicular.
Type 5's directionality depends on the exentricity parameter.
Those only affect scatering media, NOT emissive nor absorbing media.
Light shining through it will make it visible as well as any background as it is 
also absorbing.

-- 
Alain
-------------------------------------------------
"If you see me running, try to keep up."
       ...Back of bomb technician's shirt

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