1. Objects aka Polygonal Mesh (6.2)
Objects are hollow and made of faces that share common edges
Faces are considered to be outward facing
Data Structure
vertex list (geometry)
face list (topology)
normal list (orientation)
normal list ignored by uisGL
Sample Data
~grissom/367/DATA
several files “*.3vn”
Sample code
uisObject Obj; // define
ifstream datafile;
datafile.open(“file.3vn”, ios::in);
datafile >> Obj; // reads data from file
datafile.close();
numV = Obj.getNumVertices();
numF = Obj.getNumFaces();
F1 = Obj.getFace(16); // return face # 17
P1 = Obj.getVertex(3); // return vertex # 4

2. Rendering Faces
Faces are made of an ordered sequence of points (counter clockwise is the convention)
Assumed to be planar and convex
Triangles are often used
Face
uisVertex P;
uisFace F1, F2; // define
P = F1.getVertex(2); // get third vertex of face
size = F1.getNumVertices();
See documentation for additional operations
Group Activity
write pseudo code to render a face

3. Rendering Objects Pseudo code For each Face Draw Face OpenGL code
uisObject Obj; // define
in_file >> Obj; // reads data from file
for i=0 to Obj.getNumFaces()
Face = Obj.getFace(i);
glBegin(GL_LINE_LOOP);
for j = 0 to Face.getNumVertices()
P1 = Face.getVertex(j);
glVertex3fv(P1);
glEnd( );
Group Activity
Write pseudo code to render an object