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Paper Walls with Vray?
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Paper Walls with Vray? // Archive: Tech Forum
Post by MikeNTX // May 22, 2008, 12:18pm
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MikeNTX
Total Posts: 28
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I am sure this has come up before but I will ask anyway. I am working on a scene of a house that has separate surfaces for inside and outside walls. I am using a parallel light to simulate sunshine and had all of the exterior to where I wanted it. When I moved inside I noticed the rooms were lighted in a strange way. Then it dawned on me that the light was coming through the walls in a way that can best be described as if they were made of a paper. To confirm this I put a box privative between the inside and outside wall and sure enough you can see its shadow of the box on the wall from the inside. The material I am using is a normal phong and an image texture. While I can see cases where I would love this effect, say on a lampshade. I do not want it on walls that should be solid. What am I doing wrong? |
Post by jamesmc // May 22, 2008, 12:46pm
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jamesmc
Total Posts: 2566
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The first question I would ask is the shader a Vray Shader?
The second is, what properties does the material editor state for the shader? |
Post by MikeNTX // May 22, 2008, 1:47pm
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MikeNTX
Total Posts: 28
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I am using the plain Phong you can see the material settings here in the picture |
Post by TomG // May 22, 2008, 3:28pm
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TomG
Total Posts: 3397
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Hard to tell without seeing the scene - if you could upload something (or email) even with just the one offending wall and shadow casting box, that might help.
Ideas are - Are the normals reversed on the wall? (you can try flipping them to see if that solve sthe problem, or try simplifying the lighting in the scene, see if the light is actually coming "from the other side) - this is especially true if you have used a plane rather than a cube for the wall. Planes are often treated as single sided.
Is double sided rendering enabled?
Is the wall set to cast and receive shadows? Are the lights set to cast and receive shadows? What does the workspace say for the shader on the wall in case there is some "split personality" going on there (rather than the model side Material Editor that you have inspected with here)?
What happens if you disable GI? What happens if you repaint the wall with some other values in the shader / other shader?
HTH!
Tom |
Post by v3rd3 // May 22, 2008, 3:35pm
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v3rd3
Total Posts: 388
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My guess.... transparency in the material.... I had one like that some time ago and being geriatrcally inclined took 2 days to figure it out. |
Post by prodigy // May 22, 2008, 4:12pm
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prodigy
Total Posts: 3029
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In my oppinion is:
you have made that room with a cube, you are looking from the interior of that cube so the interior faces are fliped, and you have enabled "Single Side" checkbox.. |
Post by MikeNTX // May 23, 2008, 8:55am
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MikeNTX
Total Posts: 28
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Here is a sample file I made that was made in the same way as the house I am working with was made. It gets the same results as I was getting before. |
Post by jamesmc // May 23, 2008, 9:25am
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jamesmc
Total Posts: 2566
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Unless I'm reading this wrong, the shader is lightworks and has a transparent attribute. I'll let others interpret the screen shot of the LE breakdown. |
Post by Changa // May 23, 2008, 10:04am
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Changa
Total Posts: 187
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Tom is right - wrong normals. Did you import the room from another application? It is triangulated in unusual way. Try to make it by boolean shelling from a cube and cut the window then. It works correct. |
Post by TomG // May 23, 2008, 10:08am
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TomG
Total Posts: 3397
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The walls are planes - this is never a good idea in general, planes are somewhat unusual objects, and often are single sided. You can see this in real-time, when the plane is visible from one side, and not from the other.
Generally it is best to build using cubes, especially since you have in the end given your walls thickness by using two planes. One cube would do in place of those, and give more consistent results.
If you go into point edit mode, you'll find your wall only has faces pointing outward - try and select a face on the inside of the wall, and there isnt one there. This means that all rendering is being done on that outer face, which is where the shadow falls.
A quick sweep of the outer face, and an Add Face on the back of the resulting cube, fixed the problem. Now the wall correctly has two faces, one pointing in to the room, and one pointing out. Previously there was only one face pointing out, you just happened to see that same face whichever way you were looking at it before, hence the error.
Planes will add this sort of oddity to scenes on a regular basis, so working with cubes is much better as a default. A few extra vertices and faces won't add much file size to the scene, and give more consistent results in real-time and offline rendering.
HTH!
Tom |
Post by MikeNTX // May 23, 2008, 10:09am
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MikeNTX
Total Posts: 28
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Well seems this boils down to operator error and RTFM. So I will do just that and see what I can figure out. |
Post by TomG // May 23, 2008, 10:38am
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TomG
Total Posts: 3397
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I think it more boils down to planes being unusual kinds of objects :) They have no real world counterpart, since everything in the real world has some sort of thickness, whereas planes in the 3D world really have zero thickness, which makes them kind of weird.
The whole concept of having a surface that faces in one direction but is visible in another is a strange one that is best avoided at all in early days of working with 3D, just to save such mind-bending concepts getting in the way of what you really want to do, which is create your scenes and make them look good!
So I'd suggest working with cubes (and other solid shapes) is best to begin with, for just about anything. Sometimes planes are easier, primarily I think with landscape objects, but its rare that a plane has any advantage over the cube. In particular, anything where you might end up on "the other side" of the object should most likely be a cube.
Rather than sweep and add face, you could just replace the walls with cubes, easy enough to reconstruct them in this case. Let us know how it goes! I'd like to see some renders of the house - and I do think this would be interesting for when working with genuine paper walls, it's an effect that could be exploited for benefit under the right circumstances :)
Thanks!
Tom |
Post by kena // May 23, 2008, 11:36am
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kena
Total Posts: 2321
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I tend to use planes only if they are a flat surface that I will not see the other side of. Or if I want to see both sides, I make sure to check the "double-sided" Option. This is all very well if you are doing a rag, or a piece of paper that has some curl to it, but generally, cubes are a better way to go for most things.
If I'm putting up a fence using transparency mapping, and there is no chance that I will need to look at the other side, I will use a plane.
I use cubes for walls, floors, ceilings... etc. |
Post by MikeNTX // May 24, 2008, 10:59am
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MikeNTX
Total Posts: 28
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Thanks all for your help. I created the model in Rhino and I never had a problem with using planes till now. I guess I will have to go back and recreate the whole house. |
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