3D Models and Terragen - Basics

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

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j meyer

Hi y'all,
as the title suggests this thread is about some basics of modeling and/or preparing
3D models for use in TG and,maybe,related stuff.We'll see.

Let's start with creased or hard edges.
Hard edges are quite essential and necessary even for something totally rectangular
like a cube.
Here is a wireframe screenie of the 96 poly cubes.
As you can see in the above examples hard edges are important for the overall appearence
of your models especially in conjunction with TG's smooth normal feature,which is not
capable of setting one or even multiple smoothing angles.
Increasing the polycount helps to mitigate the ugly black stuff,but doesn't get rid of it.
The next example shows a UV-mapped and image textured object.
The only difference between them are the hard eges only anything else is identical.
The normal smoothing sort of visually bulges up the sides of the brick.
One of the reasons you shouldn't model or use 4 sided tree trunks btw.
Another way to get the creased edges look would be to build your model from unwelded
planes.The outer borders of the planes are automatically treated as creased by most
render engines,as far as I know.This is a common technique that's pretty wide spread.
And one reason why it's not a good idea to simply subdivide downloaded meshes to
smooth them.
Since not every modeling software exports creases with it's obj files you should test
if your app does.In case it doesn't there is PoseRay.
There is more to say about export features or P-Ray and other stuff,maybe we can
address that later.

Ok,that's it for now.

Feel free to participate.


Good of you to start this, Jochen. I never paid any attention to creasing angles in LW, and only found it's workings in Poseray. So now I haul everything through Poseray (which works better than exporting from LW), and also found that I have to unweld all in LW first, or the maps get crooked. Then weld in Poseray and set the smoothing/creasing angle to an appropriate size. So, I now tend to make layers of shapes that need different angles, for beams, slighly rounded corners of buildings, or really smooth clothing, so I can smooth each layer differently, then export.
In Speedtree even a single flat leaf can have a 'smoothing' angle so it looks rounded, which is nice for grass, by the way.
Still, sometimes I have these black triangles in TG with a smooth surface such as an arm or head, even when smoothed at 180º in Poseray. Probably not enough polys, perhaps.

j meyer

As for the black triangles I had cases were stuff like that showed up with
overlapping geometry as well.

Just to be clear with overlapping geometry I mean that a poly of one piece
of geometry is overlapping or somehow intersecting with another poly (or polys)
of the same piece.


Hi Dune,

Maybe you are referring to this kind of artifact ?

Most of the time this problem can be fixed by offsetting the shadow,

Looks like Thea manage to fix that is a more sexy way.
It's a self shadow artifact, so as you said, increasing the poly count (+ subdivision level) reduce the problem a lot.


Great thread you've started Jochen...PoseRay is more handy all the time, hadn't thought of this so thanks to you and Ulco....
something borrowed,
something Blue.
Ring out the Old.
Bring in the New
Bobby Stahr, Paracosmologist


Indeed, Jochen, that sort of thing. Sometimes I'm a bit too keen to reduce polys perhaps (cutting off legs where trousers hide them, e.g.). Who is Thea?


Thanks, Kadri. Didn't know that software.

j meyer

Well,since paq showed the jaggy shadow line in his post let's start with that.
Although I don't know of any shadow offsetting in TG I have to admit.

First image shows that jaggy shadow and in the shadow region some kind of
grid or raster.The latter is due to Gisd somehow.
On the left a pretty low poly sphere 16 segments of 8 polys.The one the right
has 64 segments of 32 polys.As we can see both of the undesired effects are
mitigated by increasing the polycount.
Here a detail shot of the 64x32 sphere.
The grid effect can be removed completely by turning of Gisd,but that's not always
a good idea,because you loose the Gisd allover of course.
The jaggy shadow line is something that can't be cured,just mitigated by increasing
the polycount.As soon as you zoom in or get closer it shows up again.Same goes for
that Gisd raster or AO facetting as I call it.
The closer the model the more polys are needed for rounded/curved surfaces.
If I got paq right other render engines might provide technical solutions for the jaggy
shadows.But that's beyond my experience and knowledge.
Here an example of that AO facetting on an actually used model.
At least one more subdivision would be necessary here - with normals that is,without
you'd need some more,because of the then missing 'smooth normals' effect all edges
would render as hard/creased edges.More on that normal stuff later,hopefully.
More to come.

j meyer

Allow me point your attention at some other little querk I came across a while
So you have your sphere model and you want to texture it in TG with the help
of the mighty Power fractal and it's many features.Maybe something like that:
You go on tweaking your PF and all of a sudden you see this:
That is what you get with 'distort normal' (warping tab) checked.
The only known solution is: don't use 'distort normal' when shading your
models and you don't like the effect.
You even get the effect with the fractal break up shader of a surface layer.Much more
subtle than shown here.Sometimes it looks like a visible seam line or so.
I have a rust shader that makes use of this effect.So it can be even useful at times. :)

Here is the official statement from back then:


About the jaggy shadow line, it only goes away when you uncheck "Do ray traced shadows" in the "Extra" tab in the Render node.
I searched to find more about it and how much it changes anything but could not find much.
Maybe it can be used in certain circumstances, i don't know.

j meyer

And one more.

Let's say you have a little low poly model that is not UV-mapped,but set up to be
procedurally shaded in TG.So,no UV's just a few parts to put different materials on.
Maybe a heli like this:

And now you want to put some dirt or color variation right on top of what you already
have.To achieve that you might choose a setup like so:

With that kind of setup you could expect to get something close to that:

And in many cases your expections are matched by the result,but sometimes you
have to be prepared to see this:

There are 2 solutions I'm aware of for this one.
The first one is to pipe the Power fractal through a Transform shader with 'use
world space' checked.Nice and easy.
The second one is to find the reason for that and to fix the model accordingly.
As far as I could find out it is caused by a messy vertex order.You need a modeler
that's capable of optimizing the vertex order to fix that.Or you could retopologize
that part in one way or the other.
In case you know other methods to fix the vertex order,please share with us.

While preparing this I separated the hull part to use that alone for the images
in this post.And to my surprise it looked different,still not correct,but definitely
So if your model is a single part model it might look like this rather than like in
the image before.

That's it for this time.

Any suggestions as to what else should go into this thread?
The stuff that came up in Michael's thread is on my list already.


July 09, 2015, 01:39:09 am #12 Last Edit: July 09, 2015, 01:43:35 am by Dune
Thanks again, Jochen. I found that no UV map often gives a very strange preview of the object, like it's all flat. Though I never rendered any without UV map. So I always UV map parts that don't need it, any mapping will do.
I often can't really get the angle right for smoothing the normals. In Poseray, standard is 35º, in LW 89.9º. For people and clothing I set it at 180º in Poseray, for say a wall with a window that has one extra poly to smooth the angle (so the angle is 45º instead of 90º), it should be around 45º I'd say, less will give a hard edge, but more often gives a strange shadow on the whole wall also. Never got my head around that exactly.

j meyer

Quote from: Kadri on July 08, 2015, 04:22:56 pm

About the jaggy shadow line, it only goes away when you uncheck "Do ray traced shadows" in the "Extra" tab in the Render node.
I searched to find more about it and how much it changes anything but could not find much.
Maybe it can be used in certain circumstances, i don't know.

Thanks Kadri.
Here is the illustration
Decide for yourself everyone.


Interesting....Great thread Jochen.
something borrowed,
something Blue.
Ring out the Old.
Bring in the New
Bobby Stahr, Paracosmologist