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Old 14-07-2006, 07:09 PM   #1
Falott
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Default creating realistic light for a lampshade

Iīm trying to light this lampshade. some of the faces are being absent to let the light shine through. I googled for quite some time but couldnīt find any helpful topics on how to light something like that. Iīm using mental ray btw.

any hints are much appreciated.
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Old 14-07-2006, 09:05 PM   #2
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2 workarounds did not work.

1) created light fog which gave a nice shading inside the lamp, but killed all the reflections on the outside. in addition, alltho with raytracing activated and a point light inside I wasnīt able to create those significant rays within the fog where the light comes through the deleted faces.

2) tried it with particles too, but that just dips everything into a homogenous nebula...

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Old 14-07-2006, 09:17 PM   #3
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does optical fx even work with mental ray? manual is no help here.
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Old 14-07-2006, 10:47 PM   #4
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yes, optical FX (like making objects glow, is what I assume you wanted) works in MR. Technically, pretty muc whatever you do should work in both mental ray and the software renderer (yes, there are a few instances where the way things are handled can generate large differences, but this shouldn't be one of them).

As for the rest of it, it'd help to know exactly what effect you were going for. Although personally I'd maybe make the lampshade either partially transparent, or translucent. Try that to start with, perhaps.
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Old 14-07-2006, 11:09 PM   #5
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to be more precise -> this lamp is like a juwel. it has a aluminium structure which holds blxk plexi-glas segments. some of the segments (more on the bottomside) are cut out to let the light shine through. the plexiglas itself is not transparent.

what I want is some light bulbs inside which light the scene - they should be visible when rendered. I need them to light the inside of the lampshade as bright as possible, allmost glowing like in real world and the light to emit through the holes and create visible rays like the sun shining through windows into a dark room with dirty air.

right now I dont get the inside lit like needed. in addition the light has influence on the outside of the lamp, which I dont understand, cause raytracing shadows is active and there is no other light source than from the inside..
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Old 15-07-2006, 01:27 AM   #6
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i meant this kind of light effect. Iīm not satisfied yet cause since tweaking the light the plexiGlas surface isnīt reflecting so well anymore.. also the lampīs inside isnt lit enough in my opinion. but whatsoever - itīs coming along.
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Old 15-07-2006, 07:05 AM   #7
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k, here's what I'd reccommend.

First off, its pointless to have more than one actual light inside the lamp, really. Yes, in an ultra-realistic render, you might want more, but it shouldn't be too big a difference for what you want. So, just make a single point light, and stick it in the middle of the lamp. And make it a bit on the more diffuse end, than on the sharp end.
Then model a lightbulb. Doesn't have to be much, really. We're going to make that glow instead. When you go to glow intensity, hit that button off to the right and assign a ramp to it - make it really intense at the core, drop quickly, and maintain a low level throughout. Also, if this is a house lamp, make the light slightly yellow - stark white is unsettling.
About the shade itself - If the inside is black, you're going to have problems with the thing appearing to be lit, wether it is or not. The lighter the color is, the better it'll show up. Try lightening the inside color. If, on the other hand, your lampshade is composed of planes, you're going to have to extrude faces so it actually has thickness (which may solve some of your other illumination problems, as well).
As for the dusty-air bit... Well, I've never messed with a lightfog, so I have no idea what would happen. But seems to me you could just throw a bumch of particles with a really long lifespan into the general area. But don't pack them too densely....

All I can think of at the moment....
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Old 15-07-2006, 08:43 AM   #8
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hi and thx a lot! Iīll try that in 3 days, when back home.

one thing you mentioned is the black color inside. alltho the whole thing is extruded and allready has thickness it doesnīt prevent the light to have effect on the outside. btw the lampshade was initially lit with a pointlight. what you see are just a bunch of spheres glowing. I did set the light up now with a spotlight, added a physical_light to its lightShader plus used a parti_volume for creating this sunbeam effect. I didnīt find any other solution with mental ray. found this tut on the net which was quite what I needed.

http://www.jhavna.net/main.php?page=scatter



again, thank you for your support. Iīll post updates later when Iīve tried your suggestions.
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