Hi, I am having an odd problem. It seems half the cylinders I make act completely irrational when the “Set Smooth” button is clicked. They basically look like their normals are randomly flipped, yet recalculating normals (in OR out) has no effect. I assume this is a known problem that I simply have not found documented anywhere?
Notice how the black spots occur? They are (as far as I can tell) not shadows, nor are they any kind of geometry. However, they are nearly impossible to remove, and successful removal is purely coincidence; there is no logical method to remove them, as far as I can see.
EDIT: Also ask yourself “how did i model this part of the mesh … or the mesh in general”. This often gives you a direction where to start looking. And explaining it to use will let us help you a lot better
Since you did do a ctrl-n for normals, you probably have interior faces. As an example: two cubes next to each other have two faces one against the other. To combine those cubes you want to remove the two face on the interior or you’ll get the black shading you are experiencing above.
I checked the link, and double-checked normals, but no, it is more mysterious than that. It occurs even on unmodified cylinders, half the time Smooth is used. All normals are correct (unless the Make Normals Outside button is malfunctioning, and it does not seem to be for anything else). I am beginning to substitute cylinders with subsurfed cubes (small extensions at the tips make them virtual cylinders), so it only slows production work a little. But the existence of this problem is causing a bit of worry in the use of Blender in our productions… Luckily, it has not turned up anywhere other than Smoothed cylinders (there was a scare about something similar in a recent Tube model, but it -seems- to have been a false alarm).
I still think that pic above is interior faces, but I’ve seen the problem in apparently fine geometry after extruding too. Check normals, check faces, as soon as smoothing is turned on the abberations appear. And, as you mention, adding a single layer of subsurfacing usually fixes the discoloration. One of the reasons I’m using a different rendering application.
Would it be possible to post a blend of the flower pot for a closer look?
I’ve seen a few smoothing problems that surface when shapes have an odd number of vertices in a circle. Changing the model to an even numbered starting circle, the problem does not occur. Perhaps a similar problem occurs with the spin dup tool? Check an “odd” and an “even” model to see if the misbehavior occurs in both.
I think I know what is happening with the flower pot. After reading Orinoco’s post it made me think. Did you model a profile and spin-dup? If so you may have wrapped the profile past the point of origin and then possibly removed doubles? This would give you the interior geometry that causes the black shading along the edges that the image you posted above was displaying. I’ve seen that anomaly like a million times any way. Two faces are on top of each other and they are sharing vertices. One way to fix would be to go into face mode and select and delete the duplicate face. If you are in fact spinning. Hope that helps. Good luck.
No, the pot is just a cylinder (with 32 ‘sides’), which was extruded a few times. There is absolutely nothing advanced about it, nor is there anything advanced about the other cases in which this problem has occured. To make things even MORE bizarre, the lines change wildly depending on angle viewed. Here are two extremes, with a cylinder 100% unmodified, except for being Smoothed. They were each rendered with the camera focus at slightly different angles, and nothing else altered.
I’ve seen exactly what you are talking about a million times. But right now, trying everything I can think of, I can’t actually duplicate the results. It would be much easier to diagnose what is up if it were possible to see a blend of your model; i.e. the flower pot above.
Is your mesh manifold? In other words does ctrl-shift-alt-m select any verts in the Edit Mode? Note that you have to be in the vert select mode and remember to deselect all verts before using the tool.
Looks like to me as well that you need autosmooth on, others cures are select the end face polys and set them to solid, another would be select the end faces and press y to split them. when the next version of blender is out we will be able to use edgesplit modifier to cure this type of thing.
And we have a winner, folks! Autosmooth on, problem gone, very nice and thank you:)
But what the devil does Autosmooth do else? The only thing else I could make it do was counter the Smooth I put on a cube; it does not seem to produce any other effects than fixing my cylinder problem:confused:
Auto smooth at rendertime automatically sets solid any face that are whithin the degr value of each other even tho you have all faces set to set smooth.
You need to understand that “SetSmooth” doesn’t actually set anything smooth at all - it just messes with the appearance (ie it’s an optical-illusion). AutoSmooth does the same but slightly more intelligently (it looks for edges). For serious work, you are generally/probably/usually better off modelling the edges with extra loops and using subsurf and SetSmooth together to deliver the desired result.
Two faces are on top of each other and they are sharing vertices. One way to fix would be to go into face mode and select and delete the duplicate face. If you are in fact spinning. Hope that helps. Good luck.
