View Full Version : refraction and transparency

08-21-2003, 08:30 PM
hey, I've been trying to have a refractive object to gradually apear over a period of time using a black and white transparency image map. but it only makes the part thats suposed to be transparent refractive and the part that's suposed to be refractive visable. in other words, I cant make an object refract unless it's transparent, so how do I make the transparent material transparent?

head worm
08-22-2003, 12:32 PM

It's quite hard to understand your problem, as you haven't explained it all that clearly.

If you want to make parts of your object transparent then you put a texture in the transparency texture channel. You can animate textures over time.

Refraction only shows up in Lightwave with transparent objects because refraction bends light passing through objects. If they're not transparent then the light doesn't pass through and so you can't see it bend!

Animating or dissolving transparency on refractive objects can create a weird jump frame effect, as the refraction will suddenly kick in when the object becomes less than 100% transparent. This is perhaps why you're also trying to dissolve the refraction, but you need to texture both Transparency and Refraction channels.

I hope this makes sense and if not, could you please explain your problem in more detail (screenshots?)


Head Worm

08-22-2003, 02:13 PM
You first have a dillema to deal with.
When it it totally transparent, you probably don't wamt to know it's there. so you dont want it to refract.
So you are may need to have to control the refractive index with the same texture as the transparency.
- really good glass is nearly 100% transparent whileryefracting like mad !
When it is invisible, the refractive index of all of it should = air.
Remember that you mar need to duplicate the whole of the exterior surface as an 'air' surface with constant refraction idex and transparency (dont forgetr to merge points)
After that I think it might get simple.
Presumabley parts of the object, when it has fully materialised, are not transparent and therefor do not refract.
You may want them to appear to refract when they are semi materialised ?

So first set up your object without rendering refraction, just get it to materialise lookin good.
then start using the same texture to control the RI of the various surfaces, to take them from 'air' value when transparent to 'full' value when fully materialised.
as your controling texture will probably have values from 0 to 100 and you will want to control the RI between something like 1.0 and 1.6 you might have to use the texture as an alpha chanel on an '6% additive' flat'gradient' white (100%) layer.
although it's difficult without experimrntin to suggest value ranges - it may be that maps in RI textures work automatically between values of 1 and 2 or something.

My brain hurts now and it's all your fault!

You owe me a pint if it works!