Blender Add-On for Jonathan Richard Shewchuk's Triangle1.6

For the generation of complicated 2D meshes like these.

Using very simplified commands (shown below)

Installation

Make triangle1.6 from source. This can be found at this repo.

Then ... Clone this repo to some folder. After cloning it, zip it up. Then in Blender, go to Edit > Preferences > Add-ons then, at the top, click Install.... This will open a file selector. Simply navigate to the zip file and select it. Done.

Steps for use

Step 1: Define something with edges

The add-on defines a Planar Straight-Line Graph (PLSG), for use by triangle1.6, from the selected edges of a blender object. For example, if we want to fill in the gaps of the geometry below (which was partially manually generated) with a triangulation,

we would first need to go into Edit Mode and select all the Non-manifold Edges, as shown here

We then exit Edit Mode.

Step 2: Generate the triangulation

After making sure we specified the path to the triangle1.6 executable we then simply click the Generate Mesh button. This will create a new object named Triangulated PLSG which looks like this

Step 3: Clean up and rejoin

The triangle1.6 executable will fill any interior holes. This would interfere with the manual mesh we already had in place. To fix this we

first select the original mesh, and duplicate it
go into Edit Mode
select all faces
Extrude them some distance in Z
select all faces again (which now includes some new ones)
Translate the geometry down slightly (press G, then Z) by moving the mouse until the extruded geometry brackets the Triangulated PSLG
Go back to Object Mode
Select the Triangulated PSLG
Add a Boolean modifier
Select the object to difference with, which will be our extruded original mesh
Hit Ctl+A to apply the boolean

Screenshots of extrusion and boolean

Rejoining the original manual mesh

There are little tricks during rejoin, like merging duplicate vertices, but most things can be googled.

How to assign materials

Materials can be assigned per face of the mesh. Practically this should be done carefully from the start so that you don't end up with a huge mesh where you have to select many individual faces.

In Edit Mode, select the faces to which you want to assign a material. Staying in Edit Mode, select the Materials panel

Add a new material slot. Then add a new material. Color it the way you like, then hit Assign. Viola!

When such a mesh gets exported to .obj format, the material names can be used to derive material id's.

ragusa / blender_triangle