DeleD Community Edition

[Grandmaster B]

Im writing a exporter that needs triangulated polygons.
I want the plugin do the triangulation.

I thought of using these vertex indices:
0-1-2
0-2-3
0-3-4
0-4-5
...

Does that work or do i need a more complex algorithm?

[Mr.Fletcher]

It will work if the polygon is convex, which would need the modeler to pay attention to, but generally is being avoided anyway.
//edit
Non-convex polygons are being avoided, I mean.
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[Jeroen]

A modeler could use the Optimize routine which will make sure concave polygons are broken into convex ones.

@Grandmaster B: are you using ear-clipping triangulation? If so, you won't need to worry about concave polygons as ear-clipping will work with those also.

[Grandmaster B]

Thanks for your answers!

I did not know the ear-clipping triangulation but it looks interesting.

[Paul-Jan]

In additional to what the others said, what you were originally doing is often referred to as "fan triangulation". Hope that helps while googling.

[Grandmaster B]

Thanks! Im currently going with the fan triangulation. But i will eventually try a triangulation that removes redunant vertices produced by CSG (vertices that visually share the same edge).

[Grandmaster B]

Hi, ive made a simple plugin that merges redundant edges. The goal was to archive a better triangulation afterwards. It works by merging edges that share the same vector (on a polygon basis) (see example 2).

Example 1: CSG united geometry triangulated (Standard):


The same geometry but with merged edges and then triangulated:


Example 2: A single polygon with many redundant edges/vertices:


After using the plugin:


You may not see the result before you triangulate your model! Also note that the plugin has no effect on already triangulated primitives, but you may "Optimize" beforehand.

The plugin destroys some connectivity on the meshes polygons what may have side effects for modelling. Also you may loose some non uniform UV mapping, but this is rare. Anyway i recommend to save a backup first.

Heres the plugin:
http://www.odagames.de/EdgeMerge.dll

This is the XML parser DLL i used, put the file into your C:\Windows\System\ folder:
http://www.odagames.de/libexpat.dll

[Mr.Fletcher]

But doesn't optimize do this too?
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[Grandmaster B]

No. Theres no easy way to do this in DeleD. Optimize merges polygons but does not remove or merge edges in these polygons (it only seems so!).

When you export for a game you always need trianglulated meshes but the current implementation produces more triangles because there may be redunant edges (for games!) in the polygons. These edges keep the geometry "solid" but may have no usage for finished work.

Example 3: A level once triangulated normally and once after using the plugin. What would you prefer in your game engine?

[Daaark]

Your shots looks cool, but the shots you use as DeleD's results don't even resemble DeleD's results. Deled turns a quad into 2 triangles, not the strange results you show off in this shot:



How the hell did DeleD turn that floor into so many triangles?

[Jeroen]

[Grandmaster B]

[Daaark]

[jwatte]

I would totally prefer the upper image. The lower image is chock full of T junctions, which can cause all kinds of render artifacts, including flying pixels, bad stencil shadows, etc.
Artists should keep meshes manifold! I'm glad that that's what DeleD does.

[Grandmaster B]

Thanks for pointing that out. True, you may not use stencil shadows with this geometry. But the edges still line up the same!

For me the second this is a optimal mesh because it saves a few polygons and is cheaper for collision detection and ray tracing. I dont need the extra triangles that keep the level meshes manifolded.