Edit the triangulation (hidden edges) of a poly (2)

[rambutan]

Hi all,
I'm trying to work out a way of getting access to the triangle data of a poly object. I need to have something equivalent to the "Edit triangulation" command in 3DSMAX Editable Poly objects. I've created a plugin to implement a custom triangulation function so the "hidden" edges don't change when you move verts etc, but this doesn't change anything as far as manually altering the hidden edges. It seems as though this triangle data is hidden deep inside the Maya core and there aren't many ways to get at it.

I know that for most application this has no effect on the look of a model and Maya taking control of the triangulation of a poly can make things easier, but we are working with low/very low poly models where every edge direction counts, but we still need the flexibility of the poly modelling tools (edge loop select, connect etc) that won't work if you bulk convert your model to tris.

If anyone has any ideas, MEL, API code or work-arounds can you please let me know.

Thanks All!!

[joojaa]

Dont double post, there are no hidden triangles in maya. Maya uses ture polygons (and indeed the renderer renders true polygons too!) not triangulated ones like max.

You could probably do a own triangluation eingene that works on some blind data tough!

[rambutan]

Maya DOES have hidden edges, they are just not selectable, even NURBS objects need to be broken down into tri's at some point in the render pipeline.

"Joojaa wrote: Maya uses ture polygons (and indeed the renderer renders true polygons too!) not triangulated ones like max. ":

Well how do explain the little dotted edge lines that appear when you enable:
Display> Custom Polygon Display> Face: Triangles

I'm not being negative, I could not find any info on this stuff whe I was searching the net so I'm just putting some extra info in here.

The solution:
This text is from polyTrgNode.cpp:

---

polyTrgNode.cpp

Description:
This node register a user defined face triangulation function. After the function is register it can be used by any mesh in the scene to do the triangulation (replace the mesh native triangulation). In order for the mesh to use this function, an attribute on the mesh: 'userTrg' has to be set to the name of the function.

Different meshes may use different functions. Each of them needs to be register. The same node can provide more than one function.

// Example:
createNode polyTrgNode -n ptrg;

polyPlane -w 1 -h 1 -sx 10 -sy 10 -ax 0 1 0 -tx 0 -ch 1 -n pp1;

select -r pp1Shape;
setAttr pp1Shape.userTrg -type "string" "triangulate";

---

So what I did was write a new triangulation function and it all works fine, can edit the "hidden" edges and still have the functionality of quads.

PS: you can find the PolyTrgNode project in the plugins folder in the devkit folder.

[joojaa]

Maya adoes not have hidden edges period! Your post actualy deomnstartes this fact.

The maya internal render does indeed render a quadrangle as a quadrangle (the maya internal one so it does not need one jaust like renderman does not either). And yes nurbs get triangiulated with a triangulation method but ist not still a hidden edge feature.

What happens when show the trianggulation:

Maya just proceeds to show how it would triangluate the poly (wich is different form a hidden line method wich is allready in a sense trangulated but your just not seing the resulting mesh). You cant acces the data because there is no data structure to controll it its just a function.

You can however redefine the function to do triangulation in another way. Its still not triangulated offcourse but maya proceeds doing it like you wish for the ogl and all renderers that do depend on triangles. Hence you only have a routine to do it your way using some extra data such as blind data on points. In wich case you could manipulete the resulting mesh! IT still has no hidden edges in its memory to be manipulated, altough now in asense it does appear to have.

That is to say it doese not work like the method in max. Where triangulation is part of the modeller

Does this make sense! As a interesting side note you cant find data on soemthing taht does not exsist. Wich is why you had porblems.

[rambutan]

Cool, I agree with you 100%. Sorry for the hassle.

Max's tri's are part of the model data, Maya's tri's are more like a render function that acts on the pure poly mesh, I think.

I was just a bit frustrated with people saying "NO, you can't do that in Maya, so don't even try.". And coming across people who had no idea you could even display the "triangles" for poly mesh.

Thanks for the info Joojaa, you've helped clear a lot of things up for me, and hopefully this might shed some light on the topic for others.