Vray Matte and glass transparency

[sine_mare]

Hi people,

So here is the problem - i have applied vray mtlwrapper as mate material on ground and wall plane, in front of wich stands object with glass:



As this is intended to be composite on photo I've checked both "affects shadow" and "affect alpha" and alpha contribution is -1. But on second picture you can see that glass is not transparent and somehow mate plane behind it makes it opaque:



Any thoughts?

Thanks in forward,

Sinisa

[joconnell]

Heya Sinisca - that happens in every raytracer full stop, the renderer sees the windows as a solid surface but bends the light through the glass to make it look transparent - I think Vlado may have mentioned a method to get an alpha but off the top of my head I'd say it's a two render job.

[sine_mare]

Hi joconnell... Sure i can see the physical limits that makes such operation difficult, but let us put aside refraction. I can't make that with simple "standard material" set to 0 opacity - even then result is the same but no refraction / reflection is made...

2 pass render is ok but if my wall behind is textured and signs on glass cast shadow on the wall (and important - shadows are from my angle seen both by the totem and through the glass) i have a problem.

If i render one pass with and one without glass i should in first pass leave my signs on to cast shadow on wall, because in second nothing will be seen behind the glass. But leaving them on, mapped on simpe standard material with opacity (as mentioned) gives also opaque area.

I have a feeling that I'm missing something so obvious, so please contribute with answers (slept for only one hour last night)

Thank you

Sinisa

[andy_butler_7]

Take off your Vraymaterialwrapper material and apply a normal material.

Select your wall and floor. Right click on them and choose "vray properties"

In the window that appears in the area called matte properties, tick the Matte object box and make the alpha contribution -1.0. Only apply this to your wall and floor. Your glass and surrounding objects should have their affect alpha as 0 (which is default) Also below there tick the shadows and affect alpha boxes.

The glass will get it's alpha value from your glass material.

This should give you a render with the correct alphs channel. If not, let me know and i'll see if i can help again.

Cheers.

[panthon]

I would use vraymaterial instead of vraywrapper. And try using alpha contribution = 0 instead of -1, and see if it works.

[Morbid Angel]

unfortinantly such thing is not as simple as one would think; when refraction is computed it no longer shows the transparency. What you need to do is render the refraction as a gbuffer pass and composite that. But I would also render the glass separetly.

[zoranm]

Sinisa,

As Morbit said, tht is the nature of the beast, but

You can get some transparency to glass material (but hard to control) if you use vray material for glass object, set up refl and refrac properties as you wish. Go to VRay:System\object settings\matte properties and set the Alpha Contribution (only) to something like 0.05 (that would be like 5% transparent, but it's just a guess because it's not linear).
This way you'l be able to see what's behind the glass.

Hope this might help

Zoran