Greetings colleagues,

I have encountered a rendering problem when using the rounded corner function inside of Keyshot on OBJ models generated in MOI— which I believe might be resulting from how I’ve been setting up my models for export (see image below).

As a new user of MOI, I regularly search the forum and web for answers to questions that come up or difficulties I encounter, however, at the end of the day, I have no way of knowing if I’ve stumbled upon the best solutions and/or answers.

When exporting from MOI, what I have been doing to date is as follows — once I have my MOI model in a condition I want to render, I save it out as an OBJ using the following settings:

• I leave the polygon setting slider in the default center position

• Output: Quads and Triangles

• Display Shaded Edges

• I tick the “Weld vertices along edges” box

• I set the Angle to 8

• In the “Divide longer then” field I type in 4 — and leave the drop down as “Curved”

• I leave “Avoid smaller then” blank

• I leave “Aspect ratio limit” blank

If anyone could be so kind as to provide me some guidance (or point me to a link) as to what it the best practice for going from MOI to Keyshot, I would be very grateful.

Thank you.

Rage on,
Ty

Hi Ty, it probably would be a good idea to send KeyShot a demonstration model where it's getting the rounded corners messed up so they might be able to figure out what's going wrong with it and fix it up in some future release.

Maybe it's sensitive to long skinny triangles (kind of looks like it from your screenshot) - if that's the case then the steps you are doing, especially with using the "Divide larger than" setting should help with that, I would think.

But it sounds like you're running into some bug or limitation in the KeyShot function so it would be good for them to know about that so they could try to improve that area of KeyShot.

Your steps sound good to me - the main thing for KeyShot will be to use either the "Output: Quads & Triangles" or "Output: Triangles only" settings since KeyShot does not like to handle complex n-gons (polygons with more than 3 or 4 sides). Other than that the other settings are just up to your own personal preference of what looks good. The ideal "Divide larger than" setting can vary depending on the size of your particular model you are exporting - if you have a model where 4 units is very small in relation to that particular model size then you want to put in a bigger value there. MoI will divide up polygons until they are smaller than the distance that you put in for that control. That additional dividing can help to make more evenly sized polygons and helps to avoid long and skinny triangles so if that's what bothers KeyShot's edge rounding that may help it.

- Michael

Hi Ty,

I would suggest to try the step file format. Usually Keyshot imports the geometry without any problems and without tesselation,
just have a go and compare the results,

best wishes !

Michael,

Thank you for the thoughtful response -- it is greatly appreciated.

I will post this on the Keyshot forum.

Also, I will likely try the triangles only setting and see what happens.

Rage on,
Ty

Ken,

Thank you -- will do -- !

Rage on,
Ty

KeyShot just has problems using round edges with polygon models, and it doesn't work with NURBS. Consider these 3 exports: 1, 2 and 3-- each of varying degrees of tessellation with the first being less and the last being the most (very much as an STL file gets tessellated when importing to KeyShot). I typically try and export my models to look more or less like #2 with medium tessellation density.



Now consider these renders in KS.



1. Shows the wireframe of each version in KS

2. Shows the max rounding corners (1). None of them do well at all.

3. Shows a decent rounding corner setting of .04 on the least tessellated model

4. Shows the same rounding setting of .04 on the most tessellated model

NOTE: Both show artifact. Perhaps there are a bit more on the less tessellated version, but not by very much.

5. A very small rounding setting of .01 of the most tessellated model. Still there are artifacts.

The round edges isn't perfect and IMO works best a very small setting with medium tessellation. HTH.

Chipp,

Thank you for taking the time to create these informative images — and sharing on what you’ve learned.

Very interesting — if not a little disappointing.

Rage on,
Ty

I'm pretty sure it's something they should enhance or fix, it looks like Keyshot rounded edge shader somehow discard the embedded vertex map. (it's a shader right ? they don't change anything on the model geometry ?)
Modo can do it, however you can't choose the minimum angle.

PaQ,


Thank you -- it is an interesting dilemma -- will continue to investigate.

Rage on,
Ty

Chipp, the artifacts are typical of polygon normals getting messed up. As you noticed , you can fix with brute force by thowing more polygons at it...making artifacts smaller and less visible, but the problem is still there And the hipoly count can be to much.

Other solution is to fix normals by hand in a 3d app. A rounded normal on the shader does this, but its a quick and dirty workaround.

With this example it is an easy fix although on a more complex model it is laborious.

The issue appears on trim edges and needs to be adressed by the exporter.

Hi 2byts,

re:
> The issue appears on trim edges and needs to be adressed by the exporter.

You mean by the importer, right? At export time the normals are all set properly in the generated .obj file - the disturbance in the normals is happening after being imported into KeyShot using its edge rounding function, not at export time from MoI.

- Michael

Hello,

Just for the record, here's a quick test using .obj format and rounded edges in Modo.
Tested with the 3 meshing options : triangle, quad-triangle, and ngones.

Ngones gives less trouble when using very draft mesh resolution (high angle value in Moi exporter).
This kind of shader is sensible to the underlying geometry ( no idea how it works :O) ), so giving a little bit of resolution in curvature (low mesh angle) helps a lot to avoid little artifacts.

Paq, the shader overides the geometry normals so you will not see normal artifacts, try rendering without it.

Maybe your right Michael about it being keyshot. I use Maya and had some normal artifacts which I manually fixed but that was some months ago...I will post updates next time i see it.

I am not sure, but would using FBX fix the issue?

Sorry 2byts, but I don't understand what you mean.

Keyshot overides the vertex normals when using the rounded edge shader, leading to render artifacts.
The images I post above show that you can have rounder edge effect on .obj coming from Moi without artifacts. (using Modo).

So it's definitively a Keyshot problem, there is nothing wrong with MoI exporter, whatever the format you use.

(FBX is usefull to handle complex ngones, at least in 3dsmax)

Hi 2byts,

> Maybe your right Michael about it being keyshot.

I don't really see how it could be other than that - the problem only happens when KeyShot's edge rounding function is being used. That's something that is happening inside of KeyShot.


re:
> I use Maya and had some normal artifacts which I manually fixed but that was some
> months ago...I will post updates next time i see it.

That's unusual - other people have used MoI's OBJ exporter to go into Maya with no problem with vertex normals.

Maybe check if you have disabled the vertex normals in Maya's importer options, or also maybe you did some vertex editing in Maya after you did the import? That may cause the imported vertex normals to be discarded.


> I am not sure, but would using FBX fix the issue?

You could use FBX for Maya if you want to, MoI also writes vertex normals out to FBX format. But currently MoI's FBX exporter does not export MoI styles as a materials list unlike OBJ and LWO format. So for Maya I'd usually recommend using .obj format, that transfers the most information.

If you run into any problems with .obj into Maya in the future please let me know, I don't think I've heard of any similar problems from any other people.

- Michael

I think he's confusing the terms of vertex normals with face normals. I dont think you will be "fixing" vertex normals in maya or other apps. Those come from the originating surface.