'Creasing' in Hexagon 2.5

Elkestra

I'm finally getting back into 3d Modelling, and dusting off my Hexagon 2.5 and Carrara 8.5. I've been looking through all the tutorials I can find, and although I'll ultimately end up in Carrara for skeletal rigging, it seems that Hexagon is the preferred box-modeller of the two. So far, so good, and my practice has been going well, except...

One Carrara tutorial showed how useful it was, when smoothing, to mark certain edges as 'Creased', so the smoothing doesn't happen there. Unfortunately, I can't find the option to Crease edges in Hexagon. :(

As long as I'm doing organic modelling, it's not such a problem, but I have several designs in mind where it would be useful, if not essential, for the look. Perhaps, I ought to move totally to Carrara for modelling, but Hexagon does seem very quick and more fluid for initial designs.

Any thought?

Elkestra
(Ann-Marie)

Roygee

Hex does not have a specific "crease edges" function, such as in Carrara, because that is a render function. Carrara has an annoying method of making edges softer than they appear in a modelling app, so for sharp edges you do need to make them creased.

However, in Hex, if you use the smoothing function under the surfaces tab, it gives you an option to use "breaks" when smoothing - edges you select under this function will be excluded from smoothing and when imported into Carrara, these edges will show up as creased.

Another method is to strengthen edges you want kept sharp after smoothing by cutting in edges close to each side of an edge you want kept sharp by using the "extract edges around" function.

Which of these functions you use depends very much on the type of modelling you are doing - for instance, with an architectural model, it is simpler to select the whole mesh in Carrara and invoke the crease edges function, whilst for an organic model where you may only want a few edges kept sharp, to use the breaks tool in Hex.

A very handy function in Carrara is the ability to apply rendertime smoothing - so you don't need to smooth in the modelling app - but do so in Carrara, so that it shows unsmoothed, but renders it as if it had been smoothed - saves a lot on polycount.

cdordoni

Roygee, Do you know if its possible to assign smoothing groups in Carrara? I just did a quick look, and it seems you can set the smoothing angle on a selection of faces, but there does not seem to be a way to save that ... unless you have to make it a separate shading domain?

Roygee

I have heard of this term, but even after looking up a Wiki, I'm still mystified as to exactly what it means and what use it has - some enlightenment would be welcome :)

If you modify an .obj in Carrara by making edges creased, and save it, it will import back into Carrara with creased edges. You can name a selection in Carrara - but that is more for making fast subsequent selections, also for making groups for using the old Poser-style rigging.

You can do partial smoothing in Hex, which imports correctly into Carrara. This makes n-gons at the interface of the smoothed and unsmoothed polys, but Carrara can handle this OK. Strangely enough, a quick test with a sphere showed that Studio, which cannot normally handle n-gons, seems to handle this type of n-gon OK and respects the partial smoothing.

I haven't done much modelling in Carrara - can't stand the VM - so hopefully someone with more knowledge can help out here :)

cdordoni

Long before there were subdivision surfaces, smoothing originally referred to setting the threshold for the difference in normals of adjacent triangles, that would result in the the triangles being drawn with a hard edge or soft edge when shaded.

This is distinctly different than sub-d surfaces.

It is useful to be able to set smoothing for normals based on selections (groups) of triangles. For example, a cut gemstone with a lot of tiny facets might render as a smooth object if the difference in the angles of the normals between the facets is small. So for that object, you would have to deliberately set the smoothing angle to a different value to get it to render as a cut gem.

Roygee

Thanks for that explanation - I think I've got it :)

Yes, in Carrara you can name a selection of edges and set the creasing or smoothing angle and it will retain the named groups after saving the file as a .car - but not as .obj, although the .obj will retain the creased edges when imported to any other app.

You can then select the named group in Carrara and change the angle of creasing/smoothing - although I must confess I found no visible difference in the render after changing the angles, so I'm missing something in my understanding.

cdordoni

Roygee said:

You can then select the named group in Carrara and change the angle of creasing/smoothing - although I must confess I found no visible difference in the render after changing the angles, so I'm missing something in my understanding.

I think you probably understand it fine. There are just not many situations where it would be that useful. Rendering a jewel is the best example I can give you for why you might want to change the smoothing angle.

Roygee

Great idea - I'll have a bash at making a jewel and see what comes of changing angles. The default in Carrara is 50 - so I imagine that if I was to select an edge to crease and the angle between the two facets was less than 50, it would not crease and would for 50 and up and Vise-versa for smoothing - must try it:)

cdordoni

The specific angle setting differs among applications. I have seen some apps that use 90 degrees as the "0" angle, or they subtract the angle value that is entered from 180, so the values are typically smaller than the ones that truly start at "0". I don't know how Carrara handles this.

Jay Versluis

Thanks Roygee,

I had the same original question today, and your answer explained it all.

Roygee

Happy to have helped :)

Something else I've recently discovered about Carrara - if, when exporting an .obj from Hex you disable exporting normals and import to Carrara using the "facet meshes" option instead of the default "vertex primitive" option, it retains the sharp edges from Hex.

So far I've only used that method on gemstones, which need the edges kept sharp and haven't yet experimented to see whether that would have any adverse effect on any other functions in Carrara.

I do know that when wanting to take it into the VM you have to convert to facets (which is pretty strange, seeing how it was imported as facets!) and it triangulates the model. Easy enough to untriangulate and it retains the sharp edges.

JoeMamma2000

I realize this issue is about to celebrate its 1 year anniversary, but....

I stumbled on it, and I'll give my 2 cents.

There is an option to effectively "crease" edges in the 3D view. And yes, Hex does "render", just not like Carrara. It renders in the 3D view, what you see when you're working on objects.

Down at the bottom of the screen there's a row of options to display the objects in anything from wireframe to shadows and ambient occlusion. There are also display options for "Smoothed solid and edges" or "Flat solid and edges". Creasing is the same as the "Flat solid and edges" option. Although it doesn't selectively "crease", it applies it to all edges.

Roygee

Actually, Hex does have a render function - see the little camera down in the bottom right. Even does AO and various lighting conditions. Pretty crude, ( I imagine it is an OGL render ) but it can give a reasonable idea of how it will render :)