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How can I accomplish proper translucency for wax?

Ok. I have been trying to accomplish this for a few weeks now.

The set up is, I am trying to identify the best approach to lighting for transparency. From the image below I've tried lighting from a particle (affecting translucency) versus dropping a point light over the surface to be lit. Also, I'm not getting the subsurface effect I am after.

The candle model itself has varying thickness's which I would expect the light to transmit accordingly through the thickness. But, I read in the docs that opacity now is used as a thickness indicator. Do I need to paint a custom map to identify the proper thickness's??

Also, the scale of the "wax" is off. Too much scattering is happening. Is there a place to set the scale for hte translucency calculations?

Lastly, the thin walls of the wax ball look like they are getting clipped, like it is not depth tracing. Maybe this is a limitation I'm not aware of.

Cool. It's a lot to ask, I'm just flat out not understanding why this is looking so crummy.

Thanks everyone. alt text

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translucency.jpg (142.6 kB)
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asked Nov 14 '14 at 06:46 AM in Rendering

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funwithayoyo
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2 answers: sort voted first

It needs to be Opaque and SSS, not Translucent.

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answered Nov 14 '14 at 02:54 PM

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Jacky
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avatar image funwithayoyo Nov 15 '14 at 03:46 AM

Hey Jacky. Changing that does indeed start to give me the effect I am after. I do notice that I am getting pretty gross banding on the edges. I thought this might be due to the lightmap settings and set an override up to 512 to see if that helped and it does not.

The particle is now NOT emitting light (since there is no translucency to effect) and a point light has been dropped down to pick up that job.

Would you know where the banding is coming from and potentially how to resolve it?alt text

opaque_sss.jpg (54.8 kB)
avatar image funwithayoyo Nov 16 '14 at 06:16 PM

After reviewing the docs again I saw it mention, "Point light shadowing not yet supported".

So, this subsurface is intended to produce a light scattering effect, with all lights but the one light type that will best describe a wax candles primary function? Providing light from a flame which is best described by a point light?

In this particular scenario would you know an alternative to using a point light to emit light that would replicate the emitting nature of a point light?

avatar image Jacky Nov 16 '14 at 06:33 PM

Sorry for the late response. Yeah, it looks like the current SSS still has limitations like that. Maybe(hopefully) Subsurface profile will solve this problem when they integrate backscattering to it. Until then you can fake it with an emissive material i suppose. You need a gradient alpha mask so that the top of the candle is more lit and it gets gradually darker towards the bottom.

avatar image funwithayoyo Nov 16 '14 at 06:45 PM

Totally cool. But, how dare you have a life outside these forums. I was going to try just that, ramped emissive.

If I may ask though, ramps. I've seen how to create one though how to do yoo control directionality. Example, I want to ramp from black to white upwards, but what if I want it reversed? a 1-minus to invert?

Or what about a ramp from left to right? Take the original and rotate it?

Thanks for your time Jacky!

avatar image Jacky Nov 16 '14 at 06:58 PM

Yeah, OneMinus inverts and CustomRotator rotates. :) Also, if you are using LinearGradient node only OneMinus will work, since lineargradient will give you both horizontal and vertical gradients as U and V so you dont need to rotate.

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I think an actual texture with some wax details helps enhance the look of the wax. alt text

a normal map will further enhance that effect ofcourse. So far what you have been doing looks fine, perhaps you hit the current limitations of SSS? https://docs.unrealengine.com/latest/INT/Engine/Rendering/Materials/LightingModels/SubSurface/index.html

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answered Nov 14 '14 at 02:29 PM

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Luos
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avatar image funwithayoyo Nov 15 '14 at 03:47 AM

Hey man, thanks for the comment. I may actually take up your recommendations. Thanks.

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