View Full Version : Corner Pannels on Sphere
01 January 2010, 02:57 PM
I tried to figure this one out for ages but its not working so i need a little help.
What i am trying to do is make hard edged pannels on a rounded surface. In this example i used a sphere, so i tried diferent things but very little success. I almost always get pinching on the corners and it just looks wrong on the model and not to mention the reflections. So i would apreciate little pointers on how can i figure this one out. Loops over entire object are not an option one way or the other.
I am modeling in max but it doesn't really matter. The principle is what i am after.
Ive attached the sphere in .obj format so you can take a look at the geometry and here is an image of the problem.
01 January 2010, 04:36 PM
I just found out an interasting thing. Not every corner is bad. Take a look at the image
So the one corner is good but the oposite is bad. I dont know if this is an smoothing error or those corners should be modeled diferently. What i know for sure is that i dont have overlapping verts. Everything is ok with the geometry.
01 January 2010, 11:24 AM
your not alone - i've allways had that trouble. have not found a solution.
so allways hidden it somehow, in texture work or other way.
01 January 2010, 10:16 PM
What is the final result being used for?
If you're after baking normal maps from the sphere for use on a low-poly object, floating geometry is your best bet. It'll result in a decent, clean bake and it's a hell of a lot faster than modeling it in.
If it does have to be cut into the surface of the sphere, then you need more geometry in your sphere to avoid polygonal tension or pinching at the corners.
01 January 2010, 10:31 PM
Thanks for the reply guys.
danshewan, no its not for game modeling, it needs to be high rez. Sphere was just an example of a curved surface, i come across this problem when modeling and it pisses me off, a lot of times i throw a model because of that. So i lived with it until now and i was hoping to get an answer so i can eliminate one thing that i cannot do from my list :)
I would like to see how would someone fix that problem. I dont care if there are 10000 polys on that corner. I just want to see it gone. So if you or anyone else can show me a wireframe of how to fix that it would mean a lot. A long time ago i leaned the best way to deal with this is with a very thin long triangle and it works everywhere exept here. It doesnt work well on corners with more than 90 degree angle. Everytime i add more geometry i get even worse corners.
01 January 2010, 10:44 PM
I'm not at my work computer right now, but I'll try and have a look at your .obj file when I get back to my desk.
01 January 2010, 12:36 AM
Okay, so rather than open up your mesh I just threw something together in Max real quick to see what's up. It's late here, so I'll go over your file tomorrow.
I used a sphere primitive, with 120 divisions and an Edit Poly modifier on it to give me some base geometry to work with. Then, I selected a rectangular set of polygonal faces and Inset them once to give me a supporting edge. Then, I did a small inward Extrude to give me this shape:
As you can see, this is Turbosmoothed to 3 iterations, with no pinching or artifacting. A very simple inset shape, admittedly, but I'll try some more complex shapes tomorrow on your mesh. A wireframe of the corners:
Like I said, I'll experiment with some more complex insets on your mesh when I've got a second.
01 January 2010, 09:39 AM
Okay, so I had a look at your mesh. Do all the panels have to be modeled into the same sphere?
I'm sure that straight-up polygonal modeling would be a better approach. The sphere you uploaded is already pretty low in terms of geometry, as you can see the faceting in the silhouette:
This extra edge you've got on this corner, for example, is resulting in shading errors.
By removing it and leaving the resulting pentagon, it results in a cleaner mesh:
Without going in and welding vertices and fiddling around with the mesh, I'd recommend examining your mesh and see if there isn't a more clean, efficient way of modeling the panel insets in that will reduce the pinching and smoothing errors on the mesh.
If the panels don't all have to be inset into a single sphere, I'd use a simple polygonal sphere with enough divisions to give you ample geometry to work with, and use supporting edges to define your hard edges and minimize on messy geometry and unnecessary vertices.
01 January 2010, 12:13 PM
danshewan, thanks so much for looking into my file. As i have sad already a sphere is just an example, real world work would be something like a car body or an airplane that is built out of pannels
That edge that cuts the pentagon, i think that is generated during the export. I dont remember cutting that edge.
Perhaps i shuld introduce a real world example. Here is a part of a Lamburghini Gallardo model that i abandoned few years ago because it had those problems.
Those two corners were problematic. The corner on the left is made in the way i would do back then and the right one is the way i would do it now. Bear in mind that this was modeled a few years ago. Perhaps the geometry is not perfect.
So i would like to see how would you or anyone else fix this. Ive attached that peace.
Btw thank you so much for your help and effort mate!
01 January 2010, 12:44 PM
Here's one possible topology. It's always a good idea when modeling car panels and such to have a parallel edgeloop close to the outside edge to tighten it up. and when turning corners it's a good idea to avoid nasty 3 point poles. And as mentioned above: sometimes N-gons will actually suit the topology better than a quad when sub-Ded.
01 January 2010, 08:28 PM
Yeah i see your point. That may be possible in this case. But what if you need to end it at the corner. Looping over entire geometry is an easy part. What i was searching for was the ability to fix that hard corner without adding loops over the whole geometry.
01 January 2010, 09:29 PM
In the example i gave above the only extra loops added are the vitally important loops which tighten the exterior edge. The rest of the red lines i've added are a rearrangement of topology. I hadn't got time to erase the original edges from the picture :D But you can see from the new topology that many of the original edgeloops are no longer needed.
01 January 2010, 10:11 PM
Ah we don't understand each other at all :( :D
Its a very old model so topology is not good. And it doesn't matter how good the topology is. What i am interested in is the corners. Can I or can I not use any kind of a technique or trick to make that corner tight without edgeloops. I know chamfering the corner doesn't work. Can i build it in a way so that i can have one edgeloop but on the corner to have 2 or 3 edges. I dont know how to explain this. English is not my primary language so perhaps i cannot explain it the best way, but if you downloaded the model, take a look at how i built the corner that i marked on the image to the right and you will understand what I am trying to do.
01 January 2010, 10:59 PM
HeHe! sorry,are you talking about the sphere above or the car panel? I know you're looking for a solution to the inset panel on curved shape but i was answering the other question you had about the car panel. :D
01 January 2010, 10:59 PM
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