Advanced 3d modelling question! CA people Help!

[Ra-az]

Hi,
I was wondering:

When creating models, does it pay to work only with triangles?
Instead of for instance rectangles.

Because:
I know from my OpenGL programming day's that OGL has to retriangulate everything that is passed to it, simply because that's the way OGL handles all geomatry: as triangles.

- The models I looked at from TW are all formed out of triangles.

- The models that I've seen created by modders sometimes have some rectangles.

Do you get a noticable difference in preformance when going either way?

Being able to work with rectangles offers some advantages (mostly for texturing). It would be nice to know this before I start creating zillions of models!



P.S. If this post should have been made somewhere else, apologies to the admin.

[wlesmana]

What I know of is that once you export the model into CAS, it morphs into triangles, as anything I imported, even my non-triangle models, became triangles.

[Myrddraal]

A rectangle is just two triangles. The poly count of a rectangle is the same as that of two triangles.

[Bwian]

Max effectively works in triangles by default. It can export more complex polygons if asked to do so, but it really does not like to work that way!

As far as the game engine goes, it's triangles. There is no real benefit to be had by modelling in anything else.

[Ra-az]

What I know of is that once you export the model into CAS, it morphs into triangles, as anything I imported, even my non-triangle models, became triangles.

Lol, could have tried that myself!! Stupid . But I'm happy with the info, will make modelling and UWV mapping a litlle easier!

My thanks to all contibutors in thread.

[Atilius]

For those who might have some interest in computer graphics arcana:

There are a number of reasons for modeling the surface of a solid as a mesh of triangles rather than as other polygons. A triangle is the 2D simplex - the simplest 2D geometrical object. Any polygon can be decomposed into triangles using a well-defined algorithm and without adding additional vertices. This is not true for other polygons.

In general, it is more efficient and mathematically safer to do many, many simple operations on simple objects (i.e. triangles) than to do fewer operations on more complex objects (such as quadrilaterals).

A triangulated surface will also tend have better integrity than one composed of some other polygonal type. When operations such as translation, rotation, and scaling are performed on a triangulated surface, all the transformed triangular facets are guaranteed to lie in a plane since three points always define a plane. The facets of a surface composed of some other polygonal type will tend to become non-planar (warp) because of round-off error in the arithmetic operations that define the transformation. This problem can become severe if these operations are repeated many times.

[Myrddraal]

The facets of a surface composed of some other polygonal type will tend to become non-planar (warp) because of round-off error in the arithmetic operations that define the transformation.

This is the reason I had always assumed was the principal reason for triagular faces. The mathematical efficiency is also an interesting point. A good read

[Ra-az]

Great post Atilius!

The way I see it there are at least 3 levels on which the data needs to be rebuild to process the model. Three slightly different platforms you could say, in no specific order:

1)3dMax.
2)RTW.
3)ISO Hardware Interface Layer (.i.e. OpenGL).

In fact, the representation and handling of graphical data can be slightly different and still render the same end-result on each one of these platforms.

I think (but in no way sure) that both 3dmax and RTW use OpenGL as their interface to the graphics hardware.
But in any case both will propably use a customized command set and a thus there will be a difference in the actual format for storing (and handling) the data between RTW and 3dmax. And the CASimporter/exporter isn't a flawless translator (allthough it's a great piece of work!)

This ALSO could result in planar troubles.


When creating a model from scratch in max, I had lots of planar problems, allthough my model was neatly triangulated ON PAPER before I started.
I also had problems like: When the model or a part of it looked fine in the game, it got inverted in 3dMax and visa versa.

Implementing this:

Let CAS do the triangulation for you and don't worry too much about it beforehand. But don't go beyond a rectangle for surfaces.

Try to work as cleanly as possible in 3dMax, by that I mean:
Keep the number of steps/operations down.
Save your work often and try to find the shortest route first, then reload and do it for 'real'.

Then Export-Import-Fix-Save-Export your model. You may need to re-import a few times.



I feel that this way you should get the best representation and performance of the data from RTW's Graphic Interface.