[Silo]Problems with Silo's normals

[Markku]

I've had Silo for a year, but started using it only a couple of weeks ago. Silo is fantastic, but there is something weird in the way it exports OBJ-files.

When I import them to Carrara 6 or Modo the faces look odd in edit and they render badly also. Clearly it is a problem with normals. My workaround is to open the OBJ's in Hex and export them again.

I Googled and found some threads with people having the same problem with Silo to Maya or XSI.
Here at Polyloop there are some who are using Silo like LoneGunman (Silo 1.4) and Mox (Silo 2.0.5) and possibly others. Are you having any such problems and if you do, then what do you do to fix the problem?

Any help is appreciated...

- Markku

[Aunty Betty]

I find that the issues you mention stem from Mirror Instance Merging of the forms where normals get screwed up even when I've attempted to unify normals. Have you tried deleting the instance and mirroring the original, then merging to see if that fixes things?

You may also wish to check this......

Before exporting from SILO go to OPTIONS>DISPLAY>OPTIONS and turn on back face culling if it isn't already checked. If you have REVERSED NORMAL POLYGONS now they will show up as spaces or holes in your model. If you have, select them and use MODIFY>REVERSE NORMALS or just use UNIFY NORMALS on the whole mesh.

[Markku]

Thanks Aunty Betty,

originally I had instances, but they were not merged.
Just to test this I made a basic cube in Silo and exported that as OBJ, imported into Carrara and Modo. The problem persists as the faces look bad in edit mode and in render.

The normals look ok in Silo (backface culling is on) and Modo also shows that the normals indicators are facing correctly in edit yet the faces look like there is something wrong in them.
It is a pity I don't have a place to post a screencapture of the case.

[jbshorty]

Describe the problem more specifically. Do you see funny black areas around some vertices. If you do, then it's more likely that Silo is incorrectly writing the vertex normal directions in the OBJ file. It may be writing the vertex normals according to the directions of it's face. To get a smooth render result in Modo, the vertex normal must be an average direction of all attached faces. This is a tricky thing, as many programs read the vertex normals in different manners. And not all programs have the tools to rewrite the normal directions. Even Modo does not, but i suggested this to Allen Hastings of Lux and he said it would be a good idea to add that feature (especially wih so many CAD folks using modo now). Time will tell...

jonah

[Markku]

It looks like a 2D gradient fill that covers each polygon every time a bit differently.
In Carrara the "gradient" is made of default orange and black, each quad-polygon face seems to have 3 verts that are source of the orange color and 1 vert that emits black.
In Modo this strange thing looks the same as in Carrara, except that instead of orange there is grey. The Modo version looks wilder than Carrara's because the 2 colors can meet in just about anywhere on a polygon's face and in odd shapes. It is like looking at a black&white fireworks show (no animation there tho).

Jonah, this is good learning for me as I did not know that vertexes have normals too. One always sees those arrows or lines pointing out from a poly's face so you think they are the only ones having normals.
Thanks for that and your help.

[Markku]

Well, I must be getting old - there is image hosting here at Polyloop. Great!
I guess the image speaks more than my discription.

[Aunty Betty]

I think this is a smoothing issue in Carrara but if you add a crease setting to remove the smoothing from the cube this should disappear.

[Piem]

Absolutely, it's even not an issue, it's normal, if the edges were creased ,they would look yellow (or blue if de-selected)
It's just that SILO has exported an unified mesh with all the vertices merged.

It's not a real problem, you can change this in the modeler or in the main room ( menu/edit/smooth object, then choose crease with an apropriate angle value - the default one is often good)

[Aunty Betty]

I agree Piem, but as a new user you may expect smoothing to be something you apply rather than being on by default. I seem to remember it caught me off guard when I first used Carrara when bringing in hard edged models for the first time.

Of note Markku for future reference if you get smoothing issues in Carrara with your mesh : Carrara has problems displaying buried or hidden polys when it comes to smoothing - this is true of V5 (no sure about v6). Something to be aware of and avoid when cleaning up your models for Carrara.

[Markku]

I hate to tell you this but you were right!
Creasing got arid of that messy look. I had become so accustomed to bringing in meshes from Hexagon which are creased by default (only now I know this), that I did not know there was any other way (Silo's way).

One extra question question for you wise men; why does Carrara show 2 normal indicators per each quad-polygon? My experience so far was that there is just one sticking out from the middle. Is Carrara a triangle sofware deep inside?

Thank you very much for your help!

[Markku]

Ooops - doesn anybody know how to crease edges in Modo?

[jbshorty]

Originally Posted by Markku

Ooops - doesn anybody know how to crease edges in Modo?

Select any edges, vertices, or faces and then use the Edge Weight tool undert the Vertex Map menu...

[jbshorty]

Originally Posted by Piem

Absolutely, it's even not an issue...

Not always true. If you are planning to subdivide the object, then Modo will smooth the vertex normals. But if you are using the mesh unsmoothed (for low-poly game model or impored CAD mesh) this can be a BIG problem... anyway, glad to see Markku got this sorted out...

jonah

[Markku]

Originally Posted by jbshorty

But if you are using the mesh unsmoothed this can be a BIG problem...

I agree.
In my particular case I was going to use the mesh unsmoothed so it is a problem because the mesh renders half black.

Thanks for encouraging me to try the Edge Weight Tool. At first it sounds a bit too propellerhead kind of tool, but it wasn't - infact it did not even fix my problem. I don't doubt the usefulness of the tool, but is there another way of getting arid of the funky look. I spun the weight dial from 0 to 4000% - plus and minus - and it did not have any effect on anything that I could see.

I have Carrara now covered, but I want those Silo meshes to work in Modo too. Why do I get this feeling that this thing only happens to me? Shouldn't there be more people asking the same thing? Or is this export/import route combination so rare - not many are meshing in Silo and rendering in Modo?

[Markku]

Ok, I got the Edge Weight Tool to work. I needed to subdivide the whole mesh, then select edges, then fire up EWTool AND click on the mesh item when I had the tool dialed at 100%.
But look at how the cube looks like in edit mode now (renders fine tho). The black "ghosting" is constrained tightly into each corner of the cube. Is that odd?


BTW, how does one zero the creasing when the EWTool has been dropped once?
BTW2, Modo's creasing is the best I've seen as you are not restricted to on/off only, instead you can have different levels of creasing. Superb!

[jbshorty]

Originally Posted by Markku

...I have Carrara now covered, but I want those Silo meshes to work in Modo too. Why do I get this feeling that this thing only happens to me? Shouldn't there be more people asking the same thing? Or is this export/import route combination so rare - not many are meshing in Silo and rendering in Modo?

Hi Markku. It's just the way Silo writes the vertex normals. I ran a test from Silo to Modo, and i found an easy way to fix it :

1. open Silo model in Modo
2. from the "Vertex" tab, run the command Split
3. then from Vertex tab, run the command Merge (at 0mm distance)

this should correct your vertex directions, and will not destroy your UV mapping...

jonah

[jbshorty]

Originally Posted by Markku

Ok, I got the Edge Weight Tool to work. I needed to subdivide the whole mesh, then select edges, then fire up EWTool AND click on the mesh item when I had the tool dialed at 100%.
But look at how the cube looks like in edit mode now (renders fine tho). The black "ghosting" is constrained tightly into each corner of the cube. Is that odd?

Using the edge weight tool will reveal the "unwelded" vertex normals once again, because you are unsmoothing them. Smoothing a mesh doesn't actually get rid of those funky vertices. It just hides them. But there are some other commands where it might cause a problem, such as any tool which reads the vertex normal directions (thicken, push, sculpting, etc). So it's better to fix it properly in the way I've described in the last post...

jonah

[Markku]

Originally Posted by jbshorty

1. open Silo model in Modo
2. from the "Vertex" tab, run the command Split
3. then from Vertex tab, run the command Merge (at 0mm distance)

What do I have to have selected?
I had polygons selected and I got succesfully as far as splitting, but the merging just increased the amount of black.
In Merge Vertices dialog there is Range, Keep... and Distance settings. Should I use range Fixed and then 0 mm distance.

Anyways, you truly seem to know your way around Modo. I've read your postings at Modo forum and I'm convinced you have a degree in Modo.

[jbshorty]

Hi Markku. Thanks, but i understand a small fraction of what there is to know about modo. These days i am using it just to make textures for rendering in Brazil for Rhino ... About your vertex problem - Remember one thing in modo. When you have no edges, vertices, or faces selected then in fact modo considers them to be ALL selected. It doesn't matter what selection "mode" you are in. Just make sure you have selected your Silo mesh in the item list, but nothing else should be selected. then run Vertex > Split. Then run Vertex > Merge at fixed distance of 0mm. After that, your mesh should be OK...

jonah

[Markku]

Hi Jonah,

I did my best to follow your instructions, but with no success.
This is what it looks like after merging. It renders similarly.



I'm not comfortable taking so much of your time as I have done so far, but I can't help but thinking wether I could post the OBJ to you somehow. Or do you have some other suggestions?

- Markku