Ray Tracing Simulation 2

1
Ray Tracing Simulation (2)
2
COMPOUND OBJECTBOOLEAN OPERATIONS ON OBJECTS

• Constructive solid geometry(CSG)
• Boolean operators
• Union
• Intersection
• difference

3
Ray Tracing CSG Objects
4
Data Structure for Boolean Objects
class Boolean public GeomObj public GeomObj
left, right Boolean()left(NULL),right(NULL)
virtual bool hit(Ray r, Intersection
inter)return false virtual void
makeExtentPoints(PointCluster clust) virtual
void drawOpenGL() // just draw its
children if(left)left-gtdrawOpenGL() if(right)
right-gtdrawOpenGL()
5
Intersecting Rays with Boolean Object

• Union? logical operators
• combInside lftInside rtInside
• Intersection? logical operators
• combInside lftInside rtInside
• Difference? logical operators
• combInside lftInside !rtInside

6
Building and Using Extents for CSG Object

• During a preprocessing step, the tree for the CSG
  object is scanned and extents are built for each
  node and stored within the node itself.
• Making Box Extents
• Union
• Intersection
• Difference

Cuboid UnionBool makeBoxExtent() Cuboid lft
left -gt makeBoxExtent() Cuboid rt right -gt
makeBoxExtent() Cuboid tmp tmp.left
min(lft.left, rt.left) //form the
union tmp.top max(lft.top, rt.top) //etc.
for the other four values worldBoxExtent tmp
//store it in the object return tmp
7
Cuboid UnionBool makeBoxExtent() Cuboid lft
left -gt makeBoxExtent() Cuboid rt right -gt
makeBoxExtent() Cuboid tmp tmp.left
min(lft.left, rt.left) //form the
union tmp.top max(lft.top, rt.top) //etc.
for the other four values worldBoxExtent tmp
//store it in the object return tmp