Artifacts in Smoothed Mesh. Help!

#1

Hello everyone,

I’m using blender 2.49

The problem is that I’m getting these lines in the smoothed mesh, as pointed out by the red arrows. How can I get rid of them ?

I just want to learn how to model things like this the right way so that I don’t have to depend on modifiers like “subsurf” to clean up after all my meshes every time.

I did recalculate all normals to face outwards.
I did remove doubles (overlapping points).
I did remove triangles (in a later post).

Here is the mesh:

Note that all the highlighted faces are coplanar (lie in the same plane - perfectly flat) from SKEY, X, 0 :

A user requested the render, so here it is:

A user requested the .blend file, so here it is:
http://home.comcast.net/~ppapostol/artifacts.blend

Any help would be much appreciated.

Thanks for your time.

Peter

#2

But the neighboring faces aren’t coplanar with them. Maybe show us the rendered result.
One way doing it “nice” maybe making them flat shaded, or using modifier EdgeSplit.

#3

Okay, I have now included the rendered image.

I don’t know anything about this “edge split” modifier. I’ll look it up in the documentation.

Thanks

#4

hm…
What happens when you add a subdivision surface modifier?
Could you include a blend file then we could take a quick look at it?
Seems you have some triangles in there, dunno if that might cause some distortion/artifacts…

-thondal-

#5

Actually at rendertime it’s all rendered as triangles,
the ‘artifacts’ are result of the mesh being shaded by interpolating the vertex normals over the mesh,
that is to say according to the shader and light angle/properties the vertexes get a color
and the faces between the vertexes are filled with a gradient value from each connected vertex to the other.

   Basically a fix is to add subdivision, off course adding subdivision(modifier) can smooth out the mesh,

but that’s why artists typically add extra control edge-loops around the important detail so detail isn’t lost.

   I hope this helps.
#6

Thondal,

Thanks for offering to look at the blend file, Thondal. The link is now in the original post.

Fktt, Thondal,

I assume that the “subsurf” modifier and “subdivision” modifier are one and the same thing.

The problem is reduced when I add it (level=2 or 3), but my animation is going to have MANY verticies, and if I add this modifier to all my meshes, won’t it slow things down considerably ?

I was wondering if there was a better way to model (I’m a beginner) so that the artifacts don’t show up in the first place.

#7

I looked at your blend file, avoid triangles at all cost in Blender. In your scene you merged everything to one vertice in the center which makes all quads in the middle into triangles.
At first I thought you had double faces, could mess with normals that.

As I understand there is a project working on support for triangles but it’s not there yet. I kind of prefer Blender as it is though, you will find ways to work around triangles.

#8

I do understand that it merges to one vertice in the default cylinder though but I find it happens when it is connected to more advanced shapes and then when you have one merged vertice the shading becomes wonky, has happened to me aswell.
Hmm

#9

yes, that’s right, subsurf is short for subdivision surface. :slight_smile:

a solution if you need to keep things low poly(eg. game art), is to bake a normal map,
that essentially bakes detail from highpoly mesh to a lowpoly mesh.

a good example in a tutorial form of baking low poly from a highpoly in 2.5 is found here:
http://www.blendercookie.com/2010/08/30/retopology-and-normal/

though the title names this as a blender > unity tut it also demonstrates normals baking in 2.49:
http://www.blendercookie.com/2009/11/21/exporting-a-lowpoly-model-to-unity-3d/

#10

God-O-Zilla,

Avoiding triangles - I didn’t think about that. A good point. Okay, I removed all the triangles. Here are the results:

I’m guessing the artifacts are coming from the coplanar polys touching the non-coplanar polys (the spokes of the wheel). But how to handle situations like this…

#11

fktt,

It doesn’t have to be low poly. I just don’t want to have to apply the subsurface modifier to all of my meshes to get rid of artifacts.

I’d like to learn how to model the right way so that I don’t have to depend on the modifiers to clean up after me every time.

Peter

#12

i think that the best solution is normal maps, how fktt said, or you can use the edge split modifier (select the edges that you want flat and ctrl+e mark sharp), as dac77 said.

must remember to read all the posts, just repeating what others already said, sry.

here is the screenshot

#13

Just select the all the faces that make up the inner disk and scale them to 0 on whichever axis is pointing up, then just reposition. S key followed by x y or z followed by 0.
Also it’s more efficient to use an array for modeling this type of thing, in this case you would only need to focus on one fith of the model and duplicate it around.

#14

I did take a look at the normal map tutorial that fktt recommended. Interesting, I never thought of this.

If I understand the tutorial right, I make a high poly model of the mesh, save the normals from that mesh. Then I put those same normals on the UV map of the low poly mesh. Something for me to try out.

Regarding the sharpening of edges with CTRL+E. It took me a little while to get the hang of the edge split modifier. This looks like a good option. Thanks for bringing this up.

handlebar,

The method that you prescribed (SKEY, X, 0) is what I used to make the highlighted polys in my first post flat. I did try to use radial cloning as you mentioned, but I had a real hard time getting the vertices at the ends to line up so that I could merge them. That’s why I started out with a cylindrical surface and extruded radially inwards.

#15

I just noticed in the screenshot you did of your selection that you’ve missed out some important loops before flattening the polys.
Just make the same selection again and expand it once to include the loops around the spokes, flatten and you should be good to go, the tris arn’t an issue on flat surfaces.
See attatchment for what your selection should look like.

#16

Also note that for the ctrl+e ‘mark sharp’ to work you need to add the edge split modifier to the object,
I would suggest ticking the ‘edge angle’ option off, so only the manually marked edges would be sharp.

#17

Thanks handlebar !

That also removed the artifacts. The only reason why I did not include that extra loop of faces around the spokes was that I thought that the smoother didn’t like 90 degree angles (looks like I was wrong). That loop of faces were at 45 degrees to make an easier/smoother transition to the flat surface.

Thanks everyone for the great tips. I learned something from all of this.

#18

fktt,

I did apply the modifier, with the edge angle button off and the “sharp edge” button on. I still got the artifacts, however. I’m new to this modifier (I’m a beginner) so I probably missed something.

I was able to get rid of them by doing an additional step after applying the modifier - increasing the flat area of the mesh as recommended by handlebar in his post #15.

#19

Ah that explains why they do work on the cylinder, thanks I didn’t know. :slight_smile:

#20

I personally would use subsurface modeling for hard surfaces, you have much more control over the poly count that way. If something is in the distance of your scene you can reduce the sub-d level, if the model is in the foreground you can increase the level.

Here’s a link to a nice site on hard surface modeling for blender, it’s always good to understand both tecniques.

http://www.rab3d.com/tutorial.html