Specular material opacity

[karanis]

Dear Juan...

I`ve seen a similar post in the forum today (posted long ago) but could not find it again to refer it. It was a tourism office scene. I think he was refering the same specific problem.

The problem is :
When you make a glass surface with a "Specular Material" (no matter smoothing or fake shadows is enabled) ; If its opacity is 100%, everything works fine BUT when you reduce its opacity (about 95% or below), the reflection on the glass surface seems spheric. I think this is an issue that refraction calculation is affecting opacity (or vice versa) but in real usage it must not.

My test scene wass something like, there are 2 parallel glasses and an object between them and you view the target in about 45 degrees camera in both H and P values.

Any comments about that ?

[juanjgon]

Can you post the image and/or the sample scene to test it here? ... I am not sure about what could be the problem.

-Juanjo

[karanis]

You are unbelievable Juan... Replied in 7 mins...

Sample scene and comparison shots are :

2 comparison with opacity diff

[karanis]

Sample scene and comparison shots are :

[karanis]

Aaaah... If an object (like a box or a rectangular prism ) with thickness, with all its polys having the same surface have "specular material" AND if it that surface have an opacity value lower than 100%, The front plane (poly) behaves as expected but the back plane is rendered, reflecting after the front plane`s refraction...

Both polys behave different. Not rendering as a solid object, all polys are rendered individually...
It must be about, what it is called "double sided surface" in LW or, must be about normal mapping for Octane. Hmmm...

Can it be the reason ???

[vanhage]

I have a similar issue in standalone when I change the opacity of a specular material. See attached.

Here I modeled the glass as a solid and when you adjust opacity less than 1, i get strange reflection/refractions. Anyone know why this happens?

[karanis]

Considering vanhage`s situation in "standalone", I think the case is about Octane engine.

My conclusion about this would be :

"Specular Material" with opacity less than 100% (1.0) should only be used with single polygonal (plane) objects. Solidified objects must be used with 100% opacity having "Specular Material". This is an Octane engine issue, not the LW plugin.

Any comments from the Octane Team ?

[gordonrobb]

Hey there. It was me that posted the Oficina de Tourismo. The issue I had was that the objects had been exported from LW in a way that messed them up. And it was if I enabled smoothing, the reflection went spherical. Not sure how your obkjects are being created, bit try turning off smoothing. Or export them differently from the programme they came from.

On a side note, I have yet to see any point in using Opacity.

[juanjgon]

Perhaps there is an rendering issue with Opacity in the Specular material, if the problem is the same in Standalone it could be a Octane behavior. Try to render this surfaces without smoothing can be a nice idea to see what happens.

Perhaps to work with architecture glass (windows and so on) could be better and faster use the Glossy material + Opacity, not the Specular material.

-Juanjo

[vanhage]

Adjusting opacity on a specular material may seem odd, but right now it is the only way i've found to remove the environment from behind a speculation object(at least in standalone, is this the case in LW as well?)

See example in earlier post I had made. The glass has no opacity and I used a black image as a backroundg but with opacity at 1, you can't get rid of the daylight environment beyond the glass.

http://render.otoy.com/forum/viewtopic. ... 05#p150205
http://render.otoy.com/forum/download/f ... &mode=view