The first task we will set for ourselves is to render a scene that contains solid objects with completely opaque planar faces and which is illuminated by one or more point light sources.
Solid objects can cast shadows.
In these two lectures we will deal with cases 1 to 3. As we shall soon see that the property of convexity significantly simplifies the rendering of opaque objects. A line connecting any two points on the surface of the object is entirely within the object. From this simple definition many other useful rules may be deducted. The centre of gravity of a solid convex object is always inside the object.