Objects

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