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Old 05-02-2008, 11:38 AM   #1
gubar
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Default Creating a lightbulb with final gather and GI

Hi,

I've been trying to create a lightbulb like effect using final gather and gi.

In the scene, there is a lamp, containing a bulb (just a lambert sphere) with incandescence (I've tried it with ambient colour too). There is a sphere containing the lamp.

The image shows the result I get. Tweaking settings, I get variations on this, though I don't get the kind of light bounce I hoped for. Couple of questions:

1) Will global illumination only work with a light actually emitting photons? I mean, it won't bounce light around if it's cast from an object acting as a light source?

2) How would you create a bulb in a setting such as this? I wanted to see what a scene looked like from a single light source, but with it's rays being bounced around the scene.

3) To make a lamp shade appear to have thickness, would you actually extrude the surface to give it depth, or is there a setting that can fake this? (with a brighter setting in this scene it is quite obvious it is a wafer thin surface).

4) Why is it that I can see the back surface colour of the shade, but not the surface closest to the camera? the shade has a high translucency setting but a very low transparency setting.
cheers,

gubar
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Old 06-02-2008, 05:49 AM   #2
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looking at the HSV settings instead of the RGB settings for the material's color, try changing the V value to over 1.000 to make the object actually illuminate the scene. i'd suggest starting at 10.000, and increasing from there if it's not enough or doesn't give you the effect you were hoping for.

at the same time though, you could just fake it by putting a glow on the sphere, and using light-linking you could illuminate the scene/lamp with a light with the settings you want.
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Old 06-02-2008, 08:28 AM   #3
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Hi,

I'm already using a very high value and this is still the result. You're right, I could just fake the effect - I would quite like to try and light a scene like this though, to see what it looks like with just one light source, dimly bounced around.

I guess this isn't the way to do it though.

Anyone else got any suggestions how they would go about this?

cheers

gubar
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Old 07-02-2008, 08:01 PM   #4
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Hi,

if you are using Maya 2008 increase the value of the scale setting on the GI tab in render globals. You can use this on a pre-baked scene. just used HSV and increase the value exactly the same as for the material. It works like an exposure setting and will brighten or darken you scene accordingly.

Hope that helps.

Gio
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Old 11-02-2008, 11:21 PM   #5
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is this setting surrounded by something like a box, simulating a room where photons can bounce back? if not it is no mystery why your front side doesn´t get illuminated, because photons wont bounce back to hit it.
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Old 11-02-2008, 11:23 PM   #6
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Thanks for the posts guys.

Got some pretty serious computer trouble that is stopping me working just now, hopefully back to it next week and I'll get working and post back then.

cheers

gubar
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