3D Models and Terragen - Basics

Started by j meyer, July 03, 2015, 03:17:21 PM

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j meyer

This second example will show one aspect of the non planar faces a bit more clearly,hopefully.

[attachimg=1]

As you can see the faces are somewhat more non planar than in the first example.
Things like that can show up on curved surfaces for instance.
And here we also see why it can be crucial sometimes to choose the triangulation variant rather than leaving it up to TG to triangulate it.
As mentioned before,usually it's not necessary to have your model triangulated,but in cases like this it's definitely better to triangulate at least some faces yourself.

The 2 variants of triangulating.

[attachimg=2]


I show these before the TG-rendered results so that you get an idea of what's happening when
importing and rendering the untriangulated model (like shown in image #1 of this post).

TG-rendered

[attachimg=3]

You see it can actually change your geometry in a way that's not desired most likely.



Think I should mention that none of my statements on modeling in this thread (or elsewhere)
is meant to be obligative or canonical.
These are rather guidelines than rules.Based on my personal experience and observations.
I don't claim them to be complete or free of mistakes.
Use at your own risk.

j meyer

Kadri - Forgot to have a look at your model yesterday.Too much other stuff in my little
          brain.Just now I thought of it again and after having a look the solution is more than
          simple.The model that's in the Project assets folder has no ngon.The shape has more
          than four corners,but it's already triangulated and thus no ngon anymore.
          And that's the reason why it renders flawless.
          Seems we had a litlle misunderstanding.Hope it's clearer now.
          Sorry for the delay.

Kadri

#92

Good examples Jochen.


Quote from: j meyer on July 29, 2015, 06:12:10 PM
Kadri - Forgot to have a look at your model yesterday.Too much other stuff in my little
          brain.Just now I thought of it again and after having a look the solution is more than
          simple.The model that's in the Project assets folder has no ngon.The shape has more
          than four corners,but it's already triangulated and thus no ngon anymore.
          And that's the reason why it renders flawless.
          Seems we had a litlle misunderstanding.Hope it's clearer now.
          Sorry for the delay.

Yes i was trying to say there that Terragen trianglated that surface without problem.

And this example is kinda the same actually. I think the problem you had even with planar ngons is similar to this.
In your train example this did not show up.But after Poseray i had no problem with it.

I exported this glass part from the same train object that doesn't show up in your image.

First i exported it as it is directly from Lightwave.
I could not see it in Terragen so much i tried. The node was there but it was like a ghost :)


[attachimg=1]




Then i tripled it in Lightwave and exported it ones more directly as an OBJ file.
This time it did show up in Terragen


[attachimg=2]


It looks like Terragen can't do the triangulating as it should on some surfaces.
How or why it happens Matt knows better.

By the way my 3D work and thoughts are always work in progress ;)
Paq or any other ones don't shy away. It is Jochen's thread but i am sure he thinks the same way (as he already said).

So yeah it looks like converting is one of the important problems especially with ngons probably.

Matt

Terragen's OBJ Reader will triangulate quads, but faces with 5 or more edges are not supported; it simply ignores them.

Matt
Just because milk is white doesn't mean that clouds are made of milk.

Kadri

#94

Wow...Very fast response, thanks Matt.
As always while you are here another question,any changes planed for this behavior Matt? :)

Matt

We don't have any plans to change this yet.

Matt
Just because milk is white doesn't mean that clouds are made of milk.


Dune

My experience in LW is that tripling/triangulating automatically doesn't always choose the most logical connections for the new edges. So I do the most important ones by hand. I don't know what Poseray does in that respect.
Also, and this may be a strange habit of mine, I don't like the messy triangles when tripling a more complicated ngon. So for house walls with windows, I usually cut the whole walls up in enough squares, then manipulate the window planes to their locations and move them inward by hitting 'b'. Instead of cutting a hole into a plane from another layer with a cube or other shape, that is.

Kadri


It looks messy but not sure how to make it look better automatically without doing it manually as you do Ulco.

If the surfaces do look good without a problem i don't care. But i know some care much more and not only you Ulco :)

Was curious and exported the original from Poseray too.
This is how the Poseray exported OBJ looked in Lightwave Ulco.


[attachimg=1]

Dune

Interesting Kadri. It's quite different. And I know, my 'behavior' is probably a bit too preoccupied with clarity. By the way, I wonder why the normals of the new planes/triangles are not centered, but sometimes on the edge. I guess that also makes a difference in how angles are calculated for smoothing.

Kadri

Quote from: Dune on July 30, 2015, 02:36:46 AM
... By the way, I wonder why the normals of the new planes/triangles are not centered, but sometimes on the edge. I guess that also makes a difference in how angles are calculated for smoothing.

Ahh that is a thing that i wanted to know too since years and always forget to search about :)
Have to look for that. Maybe others already know it here?

Kadri

#101

Ulco i asked in the Lightwave forum. Can't say anything about it but the answer is this:

"Normal that is displayed in viewport wireframe is just hint. Visualization.
Real normal vector, such as during rendering, if mesh is smooth is constantly varying.
It's interpolated across entire polygon.

Wireframe drawn normal dashed line is in center of polygon, that's it: sum all vertex positions and divide by quantity.
If you have two or more points not merged, not welded, displayed normal vector will be probably moved to direction of these not merged points.
f.e. take pen tool and make quad, drag one point with snapping enabled to one of remaining three.
It's quad poly, but looks like triangle. Where is center of displayed normal?
"

It is Sensei's answer. He is a plugin maker for Lightwave that knows what he does.You might know him.

Dune

Thanks, Kadri. I think I remember his name form the plugins indeed. Interesting. Learned something again. Nothing to worry about then  ;D

Kadri

#103
Quote from: Dune on July 30, 2015, 08:24:22 AM
... Nothing to worry about then  ;D

Yeah that was what i understood too :D

j meyer

First of all: Thank you Matt!  ;D
I for one hope that behaviour (TG ignoring ngons) won't change.

Ulco - To me it seems like a good habit. :)

Kadri - I was refering to your obj file opened in Wings3D.Which I totally forgot
          to do the day before when I just rendered in TG.
          Hope Matt's post cleared that up in the meantime.


As far as I have observed PoseRay's auto triangulation isn't better.If you need things
to be in a certain way you are always better off doing it 'manually'.
As always,from my point of view and judging by my experiences,of course.