Caltech Multi-Res Modeling Group

MeshEd Basics

Fundamental classes

The mesh topology is determined by some top level triangles we call Faces . It is roughly:

Face
{
  Face*  neighbor[3];
  TTree* root;
}

neighbor points to each of the neighboring Faces.
root points to the root of the triangle tree (TTree).

A TTree is a node in the triangle tree. It is roughly as follows:

TTree
{
  TTree*  parent;
  TTree*  children[4];
  Vertex* vertices[3];
}

It should be obvious what parent and children point to.
vertices point to the three vertices of this particular triangle.
We have affectionate names for the children; we call them T0, T1, T2, and T3. The end of this page shows how these children are arranged within a parent.

A Vertex contains some data about a particular vertex. It stores, among other things, the geometric positions of the vertex at different subdivision levels:

Vertex
{
  CVec3 val[N];
}

CVec3 is just a simple 3-d vector class. N differs for different vertices; for example, say we have a mesh of depth M. A vertex that exists at the top level will have its N = M, whereas a vertex that didn't exist until 2 subdivision iterations will have its N = M - 2. Basically each vertex has high enough N to store all of its positions.

A Mesh is simply the following:

Mesh
{
  Faces*   faces[];
  Vertices vertices[];
}

A Mesh just contains all of the Faces in the structure, as well as pointers to all the level 0 vertices.

Template structure

The simplicity of the class descriptions above is greatly exaggerated. All these classes are defined as templates. A typical definition looks like (take Face as an example):

template<..., class FaceIf, ...>
class FaceTp: public FaceIf, ...
{
  ...
};

Essentially, the classes derive from their template parameters. Since typically these classes depend on the exact definitions of multiple other classes, this gives us a good way maintaining strong type checking while letting us freely add data/method members of each of the related classes.

Layers:

RapidApp
-> Inventor
-> Geometry layer (subdivision stuff)
-> Data Structure Layer ( mesh.cpp ttree face vertex vertind vring tfetcher triind names.h)

Files:

Meshed core (templates)
- mesh.{h,cpp}
- ttree.{h,cpp}
- face.h
- vertex.h
- vertind.{h,cpp}
- vring.h
- tfetcher.h
- triind.h
- names.h
Geometry
- onering.{h,cpp} - subdivision functions and analysis
- ringcoeff.{h,cpp} - coefficient management
- subdiv.{h,cpp} - define schemes
- cvec.{h,cpp} - 3D vectors
Drawing
- drawmesh.{h,cpp} - OpenGL drawing, picking
- ivCB.{h,cpp} - inventor stuff
UI
- states.{h,cpp} - machine independent UI stuff
- controlsCB.h - abstract interface
- controlsCB.cpp - implementation
Misc
- OIio.{h,cpp} - inventor io
- cmdLine.{h,cpp} - command line args
- options.{h,cpp}
- psOpenGL.h, print.h - picture output
SGI Specific UI
- rapidapp/ (subdirectory)

Naming Conventions

Note that orientation is not implied in the vertex naming - see last diagram.

Edges are named for their opposite vertex.

Sub-triangles are named according to their nearest vertex, with T0 in the center

Sub-vertices are named for their opposite vertex.

The vertex numbers of the subtriangles are the same as the nearest vertex or sub-vertex of the parent triangle.