In the previous version of vray i was able to make a 2-sided material or skp 2sided material with one side white and one side transparant. I used this material for the ceiling of an interior so from the top view you do not see the ceiling but it does give a shadow in the interior scene. With rhino 5 and the latest vray i cannot make this work. The material is double sides the way i want it but it does not cast a shadow. I use a sun as a light source and tried both double side skp and normal double sided.
Any suggestions about what i am doing wrong?
The problem is, that there is a bug at 1.5 and 2sided material doesn’t work like before. Joe was looking at it, but doesn’t found a quick solution last. I’m not sure what the last state is. From my side I must say too, it’s a hard problem for scene setups. I hope it can be fixed.
Micha, thanks a lot. I have been trying all possible settings, flipping normals and what not. Still a pain in the ass that it does not work but i guess i have to do without it for now.
I tested it here - right, it block GI light only. So, maybe you can setup the scene so that an extra surface placed above the scene block the sun light and the invisible black light block the GI.
Hi Rene and Micha
Maybe I’m not understanding what Rene want, but the material to hide the ceiling is not the Two sided material, it is SKp Two Sided. I made a test and seem that is working fine for me.
Again, maybe I’m not understanding the effect that you want to get.
Best
In the past I used a material at the backside of a surface as background behind a train window (motion blur effect) and the lighting from outside comes in. Now at 1.5 it’s blocked. If I would change back and front material and flip the normal, than material isn’t visible from inside the room.
The Skp2Sided material behavior you are talking about was a fluke related to the implementation of that material. That was why I ended up just giving you a recompiled version of the old plugin so you could use it for your project. There is not a way for me to implement this behavior without putting that bug back in, and that bug messed up reflections/refractions, and other things.
Here is why the Skp2Sided used to work the way you want it: in certain cases I accidentally picked the incorrect side to render. In your case, it was accidentally picking the transparent side regardless of whether I was shading the front or back. This had the side-effect of allowing camera rays in, and light rays to be traced back to the camera. However, now that this bug is fixed, it will always pick the correct side: meaning the outside will be shaded as transparent but from the inside it returns an opaque material. This has the effect of letting camera rays in, but does not allow light rays to get out ( because it is opaque on the interior side now, which is correct ). That is why this trick no longer works - if light can’t get back to the camera it is dark.
You can get pretty much the same affect by just having a fully transparent double-sided material - because that is essentially what was going on in the old Skp2Sided material.
@Violine: typical it should work if the surface normal (set per _dir command) shows in the room and you set a wall material to the front side. But I suppose so it’s working in the current nightly build only, because “accidentally picking the transparent side”. So, you need to wait for the next update, if I understand right.
@Joe: What do you mean with “fully transparent double-sided material”. I need to see the background plane from inside the room, but need all lights goe’s through the plane. How do I setup a “fully transparent double-sided material”? Is it visible from one side? It’s no problem for me to setup a fresh material for my project files.
Unfortunately i cannot see your posted image because i do not have permission to see them and i do not know why. I indeed ment the skp double sided which used to work in v ray 1 but not in vray 1.5. Which version did you use?
Micha
that is a good way around but you have to put a vertical surface in the scene otherwise it will block your cameraview from above. In topview you do not see this surface at all but in perspective views you have to post remove it. Good idea!
If i understand what you want, both of these can be done with a regular Two-sided material (not Skp2side).
To make a wall transparent from one side only, but cast a shadow as if it is opaque:
On one side place a standard diffuse matl - this is the opaque matl. On the other side place a standard matl with NO diffuse layer, only refraction layer, IOR = 1.0, affect shadows = off - the surface will appear transparent from this side.
To make a wall transparent from one side only, AND cast a shadow as if it is transparent:
Same as above, but in the OPAQUE matl turn off “cast shadows” in the options panel below the diffuse layer panel.
I need a visible surface from inside, but this surface need to be transparent for GI lighting. Nothing works here, always the lighting is blocked. I very miss the option to get a visible surface that cast no shadow for any light source.
I don’t believe shadows are your problem, the problem is that the surface is opaque - light cannot penetrate it. I don’t believe there is a way to do what you are trying to do all in one material. To get light into the room it needs to be double-sided transparent. To get a background image you would need to use the scene environment, or add another plane with an image on it.
There isn’t a way to combine both aspects together in a single material. You can’t make the material transparent and make it show a background at the same time - a non-transparent image makes your material opaque, which blocks the light.
Maybe I don’t explained it right. At 1.05 it was so, that two side material can contain an opaque and a transparent (or “none”) material. For GI the front material counts only, if it is “none” or transparent, than GI light come through. I used it for train interior renderings a lot. A plane with a motion blur landscape texture was placed behind the window glass, but the GI lighting wasn’t blocked. Here you can see some images:
Now at 1.5 I would expect, the transparent side is invisible for lights/GI and the opaque side (front or back, like set) count’s for the visible side only.
I need a way to add my motion blur texture planes without to block the lighting. And shouldn’t the disabled “cast shadow” option not allow to make one side transparent for GI too? Maybe this could be a way to get the workflow working again.
Or could you add an option, that the let the old workflow working again?
Or could you make, that the transparency of the front side is used for the GI calculation of the backside?
I need a textured plane that is visible for the camera only (best for reflection/refraction too, but it’s not so important). The old skp2sided material was so extreme useful.
Thanks for your reply. I understood that it was a bug in vray. I downloaded the latest version and now it works like it did before. 2 sided skp and only a material in one slot, you can leave the other one empty. Shadow from the roof insied and you can see right through it from the outside. Easy as it is!
I will try your version though. I am only not sure about the cast shadow option. I think it only works if you use the rhino render.
I thinks you can’t make the material transparent and make it show a background at the same time - a non-transparent image makes your material opaque, which blocks the light. Thanks you :roll::roll: .
