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, iosin)
• datafile gtgt Obj // reads data from file
• datafile.close()
• numV Obj.getNumVertices()
• numF Obj.getNumFaces()

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 gtgt Obj // reads data from file
• for i0 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