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backlighting/constant refectivity issue


scottwojda

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I'm trying to backlight a plexiglass header using the constant reflectivity shader, with the texture set not to cast or receive any shadows. when I render it, the the texture is not bright like it's supposed to be, but looks like it has no reflectivity shader at all...just regular dingy gray instead of bright white. does anyone know what could be causing this problem?

-scott

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If you want to back-light something, my experience is that you can't do this by reflection, you actually need to put a light (point source) behind. If you have a large area you can even out the lighting using an array of lights. Unfortunately this does increase rendering time considerably.

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thanks a lot, i found out that i had a gray fill selected on the object, so it showed instead of the white.

DDDesign, tell me more about your idea. i design tradeshow exhibits and we are always backlighting graphics. I can't seem to get it right in Renderworks. I tried to put a point light behind it and use the plastic translucency shader, or just make it semi-transparent, but it's not working quite right.

If anyone has any good way please let me know.

-scott

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I'm using the technique to produce an object that appears luninous and also lights it's suuroundings. I put a point source or an array of point sources behing a thin translucent sheet. This diffuses the appearance of the point source - like pearl or frosted glass. I'm not sure why it isn't working for you.

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quote:

Originally posted by scottwojda:

but when you use translucency, can't you see through the sheet? which shader are you using?

To get a luninous frosted acrylic effect I'm using color= obj attribute (object fill=white), reflectivity=translucent plastic, transparency=plain transparency @60%. You may need to experiment a bit with these settings, and the strength of the light. I have it in a box with reflective back &/or sides.

Yes, the VW12 area lights will be good...

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Until 12 ships....

A simple workaround is to assign backlit objects a constant reflectivity, so that their luminosity isn't affected by other lights. Yes one can add point or spot sources behind transluscent objects, but it adds to rendering time and requires a bit of tweaking. In my experience the backlit materials never have the punch they would have in real life.

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  • 1 month later...

"In my experience the backlit materials never have the punch they would have in real life."

One little cheat that I have discovered (I run 11 at work, so I don't know if it still works in 12) is that you can give lights intensities greater than 100. This doesn't seem to add to the rendering time the way it would if you were to add multiple lights.

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