Vray ies and Specular/reflection

[cariet]

Does anyone know how to stop specular/reflections with Vrayies lights. We're trying to use them at the moment and they are working great but when we pass glass on animation it picks up the strong specular/reflection from the light source on the ies file and looks odd. Anybody overcome this problem and found a solution?? thanks

[Mikokariadis]

Hi cariet, maybe use the specular/reflection pass in post and negate its luma/chroma values from the image, usually easier with a element mask on the intended object. When the reflections are too high on some particular problem spot and I am out of time to micro tune I use that method.

There may well be another way to do it from inside the renderer but I hope this helps.

[Alan Iglesias]

It is important to realize that in a sense, there are two types of specular hilights in Vray. If your material is reflective, unless your light has Affect Reflections unchecked and you are using a healthy amount of Reflective Glossiness, it will actually create a hard hilight (the actual reflection of the light in the object) on the rendered object, even before you "create" one with the reflective material. Although perhaps physically correct, I find that this one is usually the one that is creating the problems because of the hard edges and blown-out appearance it can have.

In this case you might consider unchecking the light's Affect Reflections attribute. This will stop the light's reflection and allow you to control the specular with just the material. Notice that even though the light's Affect Specular is still checked and the material is reflective, there is no hilight rendered on the object until you add one with the material's controls.

Now, when you add the hilight with the material, you will notice that the Hilight Glossiness and the Reflective Glossiness are locked together, so in its default form the Vray material will not give you any "procedural" specular without adjusting both attributes. As you decrease the Reflective Glossiness, so will go the Hilite Glossiness and the hilight will appear and continue to grow and soften. Although it may not be always physically correct, I will often unlock the two glossiness attributes and soften the specular by adjusting the Hilight Glossiness on its own, without blurring the reflection itself with the Reflective Glossiness. I'm quite certain I've seen actual surfaces (some car finishes come to mind) that have fairly sharp reflections, but also have a softer specular due to finish and light source/flaring considerations, so I don't have a problem with unlocking these settings. Another plus here is getting a softer specular without the greatly increased render times associated with glossy reflections!

Now, will this solve your problem? It all depends on the size, strength, and proximity of your light(s). If they are big and bright and close enough, you may still have specular-oriented problems, especially in animations.

In these cases I would use your existing lights for illumination only; turn off their Specular and Reflective attributes, and create "specular only" lights in approximately the same positions that are just affecting the specular aspect of the material. You pretty much turn everything off except the specular and adjust the light's size, power, and position until the specular is doing exactly what you'd like it to do. This, coupled with the material's Hilite control should give you all the control over the specular aspect of your rendering you'd ever need.

And don't forget that you can use the Vray light Exclude functions to effectively "lock off" specular-only lights to specific objects to your heart's content.

Finally, something else I've seen is when someone is using a bitmap in the Environment Override Reflection slot. Keep in mind that if your bitmap has white or very bright areas (especially HDRIs) thse may very well appear as specular hilights on your rendered object, and as uncontrolable as they are, they can raise all kinds of havok. The way around this is to edit the bitmap in a paint program and rid the image of completely white (or very bright) areas, leaving the specular aspect of your rendering to your complete control.

I don't know if this will help your IES-oriented problem at all, but I've seen folks have a considerable amount of problems with specular hilights in Vray so I thought I'd add thse comments for the forum at large.

The whole specular thing in Vray can be pretty complex I guess, but ultimately with power comes complexity and I appreciate very much the power Vray gives you as a renderer, both as a physically correct one, as well as one that allows artistic license and production-oriented control.

I hope this is helpful,

-Alan

[cariet]

Thanks for the info alan, think francesco should employ you for his next "complete guide" book!!. I learn't a lot from what you said and certain parts make sence. I am however unable to uncheck affect reflections or affect specular using vray ies lights. If they had a check on them like photometric lights then there wouldn't be a problem as what you mentioned above would solve it. Photomeric lights on the otherhand allow you to turn off affect reflection affect specular BUT the render times we're massive in comparison to the vray ies lights, so I'm after a solution that allows me to to keep the vray ies file but turns off the reflection/specular. Thanks for your help.

[cariet]

Thanks for the work around Mikokariadis, I'm looking to sort the problem in max first and if I can't I'll use your method, sounds like a good solution - thanks.