Hey Community,

i have a file in which "weird" lines occur if i export as .obj .stl .3ds and so on. I reall tried them all.

I need to export it as smooth surface as possible and import in blender.

Please have look at the attaced file.

I want that the lines near to the stripes (booleaned stripes) do not occur. It kills the smooth surface.

I am very thankful for every help !

Thank you so much

could you post the 3dm file?

I looked at the OBJ file, why so heavy on the mesh. Export from MoI using the defaults possibly even lower, then use the SubD or smoothing from Blender to adjust the mesh density to what you want. I have had the same problems with OBJ being imported into other packages where the other app says that there are shared vertices and they cause these problems you are seeing here, where the Poly surface is drawn into the middle of the one before as if it was trying to triangulate but then it leaves the gaps. I hope i have that right ... But for me the cure was to model in MoI and then export out as quads and tri's and to lower the resolution on the mesh to being really coarse allowing the poly-modelling app to take care of the smoothing and SubD stuff.

HTH

Martin Spencer-Ford

Hi sosodef, unfortunately it's a general problem with Blender - Blender does not process the vertex normals smoothing information in the OBJ file, and because of this it tends to render CAD data with various kinds of shading artifacts.

That's pretty much a problem unique to Blender, every other rendering program that I know of is able to use vertex normals from OBJ files, so if you used a different rendering program that problem would go away.

There has been some talk by the Blender devs that this problem will be targeted to be solved in the next major Blender release, so once that release is out Blender should work better for rendering CAD data but right now it just does not really work very well for that purpose.

See here for some previous discussions on this:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4272.1
http://moi3d.com/forum/index.php?webtag=MOI&msg=4515.3

- Michael

Hi sosodef, for example here's what your same posted .obj file looks like when rendered in Cinema4D - note that when the vertex normals from the OBJ file are used by the renderer it helps to make very smooth looking surfaces in the rendered result:




One thing you could do in Blender to reduce the shading artifacts somewhat is to make a more finely diced up mesh, since the object is only gently curved in the long direction using just the "angle" parameter alone will not generate very many polygons in that direction, but you can use the "Divide larger than" setting to force the mesh to be more finely diced up and that will tend to reduce the kinds of shading artifacts that Blender will produce to be smaller in size at least. See here for a demo of using "Divide larger than":
http://moi3d.com/forum/index.php?webtag=MOI&msg=2833.5

But as you can see from the above quick C4D rendering, it's really better to use a rendering program that will read the smooth shading information that is stored in the OBJ file and use it when doing the rendering, it greatly helps to make the rendered result look the same as the original smooth NURBS surface did.

- Michael

Hmm this thread has tweaked my curiosity - In the screen shots i have taken are from Silo - The sample that michael shows is in the first grab and is indeed a fine mesh, but then if i scroll over to the next body section you can see clearly what i was trying to say, see how the vertices are all disturbed leading to faces pointing in the wrong direction. Silo is just a modeller, with SubD support and UV tools, does this mean that Silo has the same problem as Blender ?

Which problem are you referring to Sosodef ?

Martin Spencer-Ford

Hi Martin, did you apply any modifiers to the mesh like doing sub-d smoothing on it in Silo? If so that will probably generate a kind of mangled result, in order to do sub-d smoothing very well the mesh needs to be specifically constructed to have a sub-d friendly topology.

If it just looks like that during modeling time it's possible that Silo just does not display smooth vertex-normal shaded stuff for it's real time display, a modeler's real time display is not really designed to look the same as a "final quality" renderer is supposed to.

So I really wouldn't make any judgement on what Silo is doing just based on their real time display, you would need to export out from it in OBJ format and bring that into a rendering program to do the actual render.

- Michael

Hi Michael, that's just the OBJ file as provided by Sosodef, If i turn on shaded mode it displays fine and the smoothness requires no additional SubD tweaking, but if Sosodef was/is trying to clean up the mesh in the hope of getting a better result in Blender then as can be seen with the vertices he would be in for a pretty hard time. I also tried the OBJ in Modo701 trial version too and had the same result, smooth display but in Modo when rotating around the object certain areas showed signs of creasing, strangely enough though not in the area that i was expecting.

Martin Spencer-Ford

Hi Martin,

> smooth display but in Modo when rotating around the object certain areas showed signs of
> creasing, strangely enough though not in the area that i was expecting.

So do you mean in a fully rendered result or are you talking about creased appearance only in the real-time display.

Just in general real-time display mechanisms take various shortcuts in order to increase speed which can tend to give more artifacts particularly with long skinny triangles like this was meshed with. That's because usually a realtime display does "Gouraud shading", where the full shading is only calculated just at vertices and then the in-between stuff is only color interpolated between those. That's gives a cruder but faster result than what a full render does which is more like evaluating the shading at every single point instead of only at polygon corners.

So it's not particularly unusual for there to be some kinds of additional shading artifacts in a realtime display that won't necessarily be in the full render, I'm not completely certain but it seems like that's what you're talking about here.


But it can be kind of good in general to avoid especially long and skinny triangles though, and using the "Divide larger than" setting when generating this mesh would help to generate more evenly sized polygons instead of ones that are long and skinny in one direction. There's a demo on using "Divide larger than" here: http://moi3d.com/forum/index.php?webtag=MOI&msg=2833.5


- Michael

Hi Michael - The result is strange, in speed render/editing mode there is no creasing, but in the full render that Modo uses then the creasing shows ...

It's all very strange to me - This is why I said I have found with some models it's better to export as a coarse mesh and then edit it within the rendering package if it supports mesh editing of course, which in Blenders case is true. The final screenshot is from Keyshot, which shows no problems at all - Horses for courses by the looks of things

Martin Spencer-Ford

Wow,

thank you all for the great comments.

A special thanks to Michael Gibson, this was the solution. I tried the Step by Step Tutorial and it workend perfect even for Blender !

To my other friends, thank you so much for your comments i read them all. Unfortunately im not used to other Rendersoftware than Blender. For this reason i will reply for each Software. I hope it will help non blender users :)

Hi Martin,


> but in the full render that Modo uses then the creasing shows ...

That's looking like a different kind of rendering artifact called "self shadowing" that can happen with raytraced shadows. It's probably possible to avoid it by adjusting some kind of shadow bias factor. Or you might try scaling your object up or down to match what Modo's built in shadow ray bias distance setting expects for objects to be generally sized at.

It's also possible that making a more regularly diced up mesh instead of one with long skinny triangles in it would help somewhat to avoid that kind of artifact as well, but I'd think that adjusting the bias render setting should do it, look for a setting like "self shadowing bias factor" or something along those lines - it probably needs to be bumped up.

You won't see any artifacts from raytraced shadows in the realtime modeling view because it's not doing shadows there.


> It's all very strange to me - This is why I said I have found with some models it's
> better to export as a coarse mesh and then edit it within the rendering package if
> it supports mesh editing of course, which in Blenders case is true.

I'd pretty much always recommend the reverse of this - just in general a more finely diced mesh will help avoid various kinds of rendering artifacts.

Some render engines may have other various settings that affect the render and the settings can be size dependent, I think that's what you're seeing with Modo there. To solve those you have to adjust the rendering settings, not really do anything different to the mesh itself.


> The final screenshot is from Keyshot, which shows no problems at all - Horses
> for courses by the looks of things

Keyshot probably does a better job of automatically managing this particular kind of render setting for you, probably in Modo it's a setting that needs to be manually adjusted to match the size of the objects that are being rendered.

Keyshot is sort of overall focused on trying to make rendering more of a single push-button thing without needing a lot of settings to adjust in order to tune things as is often the case with most renderers.


- Michael

Keyshot or SimLab Composer who is more affordable( it's has the same Luxion render engine inside)
all is made for an easy use! :)
http://www.simlab-soft.com/3d-products/simlab-composer-whats-new.aspx

Actually Pilou, Simlab now use their own developed render engine technology in V2014 not Luxion.
http://www.simlabforum.com/viewtopic.php?f=12&t=7010#p10014

-

Ah thx for the info!
Luckily i have only spoken of that only in this forum! :)

Guys,

here is my next question to this. Didn´t want to open a new thread, or should i ?

How can i "fillet" smoothen the sharp edges of the "stripes"

If i try fillet with all Option G1 - G3, circle and so on, no smoothening of the sharp edges appear..

Any solution ?

Thanks in advance !

Hi sosodef, what fillet radius are you trying to use? It looks like probably only a pretty small radius will fit in the space you've got there. Try going down in increments of 1/10 like try a radius of 0.1 or 0.01 and see if that produces a fillet. If it does then it means your original radius value was just too big to fit in some of the corner areas of your shape.

If you need more help please post the 3DM model file that you're trying to fillet, that will make it possible to take a look at your geometry and maybe give some better tips.

- Michael

Hey Michael,

it is about the same model which i uploaded before in this Thread. It is about the "weird lines" object.

In this file you can the "stripes" right, which are boolean cutted... I tried 0.1 mm and lower... unfortunately i could get no any results.

Is it possbile, that i just cant see the "filet" if i choose 0.01 but in fact it is "there" ?? If yes, isn´t 0.01 mm filet also pretty close to a really sharp edge ?

Thank you in advance.

Hi sosodef,

> it is about the same model which i uploaded before in this Thread. It is
> about the "weird lines" object.

Ok, but you never attached the 3DM file for this model, as far as I can see you only attached the OBJ file. I can't try to fillet the OBJ file, I need your 3DM model file in order to look at any fillet problems.


> If yes, isn´t 0.01 mm filet also pretty close to a really sharp edge ?

It depends on the particular scale of the particular model.

It's hard to give you any good information without being able to examine the 3DM model file that you're having problems with. Please post the 3DM model file (not just the meshed OBJ one) and that would help me to be able to take a look at what you've got and try to give you some tips.

- Michael