I have seen this problem once before, although for the life of me I can’t remeber the thread. It dealt with some artifacts in a raytraced reflection. Well, I have hit a similar problem, although my material is glass, not metal.
Before I begin with my theories, I’ll give basic stats for the file. The model is a Naboo Starfighter. It is a 3ds model, not of my own creation, that I imported and remapped. The one you see is the “High Poly” version. The Low Poly imported and rendered fine, no glitches in the galss. It is an internal Blender render, OSA set to 8, no AO.
As soon as I saw what rendered, I recognized the problem from the other thread, and then I took steps to figure it out. First, I thought it was the normals, so I recalculated. The normals were fine to start, but better safe than sorry. Recalulate, rerender, same problem.
My next step was to remove doubles (maybe there were two windows in the same object), recalc-norms, rerender. No dice, same prob.
So, I concluded that maybe it is the number of objects underneath, and then took steps to test my theory. I singled out my Window in anther layer and used a simple cube, dupliverted along a line with over 70 vertice, going almost straight out from the camera, under the glass. Render, but the problem is gone. Maybe not the number, but the objects beneath (maybe one or a group). There is also the possibility that the render doesn’t treat dupliverts as “real” objects, which I tested in a later step.
Now, I’m going through and moving one object at a time into a different layer. Each time I did so, I would render the picture with the window and the new layer for the cockpit. I repeated this step until I encountered the problem again, which was when I had the whole cockpit plus the upper hull in the view window. So, I assumed that it was the upper hull causing the problem. With that in mind, I moved the rest of the cockpit into another layer and rendered with only the hull and window in view. No dice, problems gone. The possibility of it being just a certain group of objects is something I didn’t really want to try because of the immense amount of possible combinations that it could be.
Then, I decided to render the ship, without the window, and add a glass plane above it to see if the problem would resurface. Render, no problem. So its not the objects in the cockpit, so it must be the window. But, when I render the window alone, I get no artifacts. Maybe another window?
I decided to borrow the window from the low poly model in hopes that it would render right. No dice, problem still occurs. Maybe its the shape of the window?
I created a sphere (with an inside and an outside) with the same general shape as the original window. Gave it the glass material, and rendered. No problem.
Right now, I’m out of options (that I know of), and the headache from it is getting pretty annoying. It might just be an occasional fluke, but I’m hoping that someone could help me solve this problem. If all else fails, I’ll just make another window and leave it at that, although I’m not sure how the original creator would take that. Please, if anyone has any other options, I’m all ears.
The first picture is rendered with a window, the second without the window.
EDIT: That should have been common sense to me. I don’t know how many threads I have read where the pictures are too small or too dark. My sincerest apolgies. P.S. Unified render doesn’t work either. I’m thinking I might be in the wrong forum (should go to rendering, not modeling). I thought this might be a mesh problem. Still no clue.
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