light through curtains


#1

Curtain Material
Hi, I was wondering how I would go about making a material for a set of curtains in a room. The curtains are closed in the scene, so you cannot see any direct light passing through the window and into the room. I would like to create a material that is is not transparent, but you can see the intense sunlight hitting the back of it where the window is. Is this possible, and if so how would you create this material. Here is an image from cgarchitect which kind of relates what I am trying to say.

Could this effect be faked if a material could not be made. Maybe placing a light inside the room, making it look as though the light was passing through? I am working with MAX 6.
Any comments will be appreciated. Thanks


#2

not sure how you would do this in 3ds max but there’s a simple hack :

  • place a (directional) light outside
  • render a shadow map (with window frame - but not the curtain in it)
  • render the curtain with a material that has normals pointing inside the room (making the assumption that the lighting operation won’t cull the light because it’s not facing the surface)

#3

I see what you mean…

It’s called SSS (Sub SURFACE SCATTING)
Theres a shader called WAX in brazil R/s , which have no Transperency,but like in wax/candle/skin etc. you can see the light hitting the object from its back.
Look up for the wax shader in brazil, under Brazil advenced material.
and try looking for a good tutorial for it…
I’m very sure It will be helpfull for your request…
Good luck
Idance


#4

You really don’t want to do subsurface scattering for such a thin material like this. When did you ever see curtains that were made of wax?

Just do what shehbahn said. Use a shader that allows you to do the illumination with the normals pointed the other way, or both ways and add the two.


#5

Actually, as I understand it EVERYTHING except metal scatters light below the surface ( according to a presentation Henrick Wann Jensen gave at our Siggraph meeting)
This QTVR of my house has a curtain like that. Its very low poly and rough, but you get the idea
http://www.rastermon.com/Rad/Bedroom.htm
Rendered in Radiance with a trans material


#6

Actually, EVERYTHING, INCLUDING some metals scatters to some degree… but would you use a subsurface scattering shader for a metallic surface? No!

Would you model every little house in every little country for a shot of planet earth from space? No!

What I’m trying to say is you need a little perspective. If you say “that’s translucent, I must use subsurface scattering” without thinking about what the effect you actually need to achieve is, you’re going to end up with huge render times! :slight_smile:


#7

With finalRender, in fradvanced material, you can set refraction ior to 1 (so it is transparency) and then set some blurry refraction. It is very fast and simulate very nice light through curtains. Maybe such technics is also possible with your renderer ?

Kib


#8

I also think that subsurface scattering would be total overkill for this situation, go for the trick with the reversed shading normals. Depending on what software you use, the default shader may already offer this feature (the programs I use the most call it “translucence”) or might be a 3rd party shader available that does this.


#9

Is that what’s called “translucence” in Maya or something else?


#10

Possible. I will have a look at it once I have installed PLE 6.


#11

I checked, translucence in Maya is that (tested it in PLE 5 with the Maya software renderer; don’t know if MR does that, that PLE 6 download server is incredibly slow).


#12

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