Introduction to 3D Graphics and VRML

Geometric primitives

Triangles

• Most primitives based on triangles
• Vertex v(i) is x,y,z
• Triangle has three vertices (!)
• Vertex structure can contain additional information
• Counter-clockwise vertices, triangle front-facing
• Clockwise vertices, triangle back-facing
• Back-facing triangles usually not drawn

Polygons

• Three or more vertices
• Must be planar

Tristrips

• Group of triangles, each of which share two vertices
• Stored as a list of vertices
• More efficient storage and access than plain triangles

Polystrips

• Triangles share a common vertex
• Efficient storage and processing

Pmeshs

• Group of faces
• Stored as two lists
  1. List of vertices
  2. Face definitions in terms of list indices into list 1
• Efficient storage and rendering

Vectors

• 3D lines

Point Lists

• Group of points
• Useful for drawing airfield landing lights, for example