Meshes

This tutorial walks through the basics of MCUT, showing how to define a mesh and iterate through its vertices and faces.

A mesh represents a two-manifold surface, where each edge is incident to one or two faces.

An example of a 2-manifold mesh.

Meshes in MCUT are represented as simple arrays of builtin C/C++ data types. In particular, users are permitted to use three C/C++ types when specifying vertex coordinates. These are float and double.

32-bit float vertex arrays

The following is an example of how to define a mesh using the float data type to represent vertex positions:

McFloat pMeshVertices[] = { // xyz|xyz|x...
  -10.f, -5.f, 0.f, // vertex 0
  -10.f, 5.f, 0.f, // vertex 1
  10.f, 5.f, 0.f,
  10.f, -5.f, 0.f,
  5.f, 0.f, 0.f,
  0.f, -5.f, 0.f,
  -5.f, 0.f, 0.f,
  -10.f, -10.f, 0.f,
  10.f, -10.f, 0.f,
  15.f, 5.f, 0.f,
  15.f, -10.f, 0.f
};
McUint32 pMeshFaceIndices[] = {
  0, 6, 5, 4, 3, 2, 1, // face 0
  0, 7, 8, 3, 4, 5, 6, // face 1
  8, 10, 9, 2, 3 // face 2
};
McFaceSize pMeshFaceSizes[] = {7, 7, 5};
McUint32 numMeshVertices = 11;
McUint32 numMeshFaces = 3;

64-bit double vertex arrays

Using the same mesh example, the following except shows how to specify vertices as an array of double:

McDouble pMeshVertices[] = { 
  -10.0, -5.0, 0.0, 
  -10.0, 5.0, 0.0, 
  10.0, 5.0, 0.0,
  10.0, -5.0, 0.0,
  5.0, 0.0, 0.0,
  0.0, -5.0, 0.0,
  -5.0, 0.0, 0.0,
  -10.0, -10.0, 0.0,
  10.0, -10.0, 0.0,
  15.0, 5.0, 0.0,
  15.0, -10.0, 0.0
};

Accessing mesh elements

As a simple demonstration of the mesh data structure defined above, let us iterate through the vertices and faces of the mesh.

// vertices
for (McUint32 i = 0; i < numMeshVertices; ++i) {
  // assuming float
  McFloat x = pMeshVertices[i*3 +0];
  McFloat y = pMeshVertices[i*3 +1];
  McFloat z = pMeshVertices[i*3 +2];

  printf("vertex: %f %f %f\n", x, y, z);
}

// faces
McUint32 base = 0;
for(McInt32 i = 0; i < numMeshFaces; ++i){
  McUint32 numFaceVertices = pMeshFaceSizes[i];
  printf("face %d (%hu vertices):", i, numFaceVertices);
  for(McUint32 j = 0; j < numFaceVertices; ++j)  {
    printf(" %u", pMeshFaceIndices[base+j]);
  }
  printf("\n");
  base += numFaceVertices;
}