View Full Version : Additive reflections in Softimage?

05 May 2011, 06:50 AM
Hi there,
I haven't had much experience with shaders in soft so I thought I have a bit of a go. One thing that I found really weird is that reflection doesn't seem to work in an additive way. I had a transparent glass object and as if i make it 100% reflective it goes opaque.
What is the deal with that? I'm kinda stuck at stage one here. if anyone could give me a pointer it'd be great.

05 May 2011, 07:45 AM
What are you trying to achieve? Reflections doesn't really work in 'add' mode, it's more 'blend' mode (speaking photoshop-way).
If you want to add reflections in non physical way turn off energy conservation or mix-add two materials (second black with reflections only).
Of course when speaking of glass, the fresnel effect is most important (its default off for reflections in mia material/architectural material)

Quoting manual:
1.4.2 Conservation of Energy

One of the most important features of the material is that it is automatically energy conserving.
This means that it makes sure that dif f use + ref lection + ref raction <= 1, i.e. that no
energy is magically created and the incoming light energy is properly distributed to the diffuse,
reflection and refraction components in a way that maintains the first law of thermodynamics4 .

In practice, this means for example that when adding more reflectivity, the energy must be
taken from somewhere, and hence the diffuse level and the transparency will be automatically
reduced accordingly. Similarly, when adding transparency, this will happen at the cost of the
diffuse level.

05 May 2011, 03:27 PM
You can render the reflections as a separate pass and then composite them in the XSI build in compositor or in After Effects. That way you can make them as strong as you want.

This is very newbie help, so first I apologize if its not your case: If you dont see the reflections, perhaps your object is alone and it is reflecting black (thus opaquing the object), to avoid that you can create a sphere with an hdri texture, or go to the pass options to add an environment so your glass material have something to reflect, or you can create white cards (grids with a white constant material) so your glass can catch the luminosity of the cards.

05 May 2011, 01:13 AM
Hey guys,
Thanks. I've gone for the mix 2 colours and it's working fine. Just out of interest though, how do you turn off energy conservation?
As for the Arch & Design material, I generally like to put everything together myself as separate elements so I have steered clear of this kind of one material to rule them all solution but I might have to check it out. It does look good.

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05 May 2011, 01:13 AM
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