This document discusses techniques for optimizing 3D game engines, including binary space partitioning (BSP) trees, potential visibility sets (PVS), lightmapping, and collision detection. It introduces BSP tree generation by recursively splitting polygons into positive and negative sets. PVS are pre-computed to determine which sectors and portals are potentially visible to accelerate rendering. Lightmapping calculates light intensities in each sector using radiosity with PVS to limit calculations. Collision detection uses the BSP tree for fast queries. The document also briefly mentions Fake III, a game engine that utilizes these techniques.

1. BSP
(Binary Space Partitioning)
Lee SangHoon

2.  Introduction
 BSP Generation
 PVS (Potential Visibility Sets)
 Generating Lightmap
 Collision detection
 Introduction of Fake III
Contents

3.  Fast collision detection
 What is not seen, is not drawn
 Lightning calculations of the map
 Can be used to optimize networking
Introduction

4.  GENERATE-BSP-TREE (Node, PolygonSet)
◦ 1 if (IS-CONVEX-SET (PolygonSet))
◦ 2 Tree ← BSPTreeNode (PolygonSet)
◦ 3 Divider ← CHOOSE-DIVIDING-POLYGON (PolygonSet)
◦ 4 PositiveSet ← {}
◦ 5 NegativeSet ← {}
◦ 6 for each polygon P1 in PolygonSet
◦ 7 Value ← CALCULATE-SIDE (Divider, P1)
◦ 8 if (Value = INFRONT)
◦ 9 PositiveSet ← PositiveSet U P1
◦ 10 else if (Value = BEHIND)
◦ 11 NegativeSet ← NegativeSet U P1
◦ 12 else if (Value = SPANNING)
◦ 13 Split_Polygon (P1, Divider, Front, Back)
◦ 14 PositiveSet ← PositiveSet U Front
◦ 15 NegativeSet ← NegativeSet U Back
◦ 16 GENERATE-BSP-TREE (Tree.RightChild, PositiveSet)
◦ 17 GENERATE-BSP-TREE (Tree.LeftChild, NegativeSet)
BSP Generation

5.  Convex set
BSP Generation

6.  CHOOSE-DIVIDING-POLYGON
BSP Generation

7.  CHOOSE-DIVIDING-POLYGON
◦ Loop to find the polygon that best divides the
set.
 Count the number of polygons on the positive side,
negative side.
 Compare the results given by the current polygon
to the best this far & set the new candidate.
◦ return BestPolygon
BSP Generation

8. BSP Generation

9. BSP Generation

10. BSP Generation

11. BSP Generation

12. Portal Rendering

13. ◦ RENDER-PORTAL-ENGINE (Sector, ViewFrustum)
 for each polygon P1 in Sector
◦ if (P1 is a portal and INSIDE-FRUSTUM (ViewFrustum,
P1))
 NewFrustum ← CLIP-FRUSTUM (ViewFrustum, P1)
 NewSector ← Get the sector that is connected with the
current sector through portal P1
◦ RENDER-PORTAL-ENGINE (NewSector, NewFrustum)
◦ else if (P1 has not been drawn yet)
 draw
Portal Rendering

14.  Portal Rendering Problem
◦ Occurs calculation and clipping when drawing
the scene
 Solution
◦ PVS (Potentially Visible Set)
 Calculation is done in the pre-rendering of the
map
Portal Rendering

15.  Distribute sample points along the splitting planes in the
tree
PVS

16.  RAY-INTERSECTS-SOMETHING-IN-TREE (Node, Ray)
 If the ray spans the splitting plane of this node or if the ray is
coinciding with the plane, send it down to both children
 If the ray is only on the positive side of the splitting plane send
the ray down the right child. The or in the if statement is because
one of the points might be coinciding with the plane.
 If the ray is only on the positive side of the splitting plane send
the ray down the right child. The or in the if statement is because
one of the points might be coinciding with the plane.
 There was no intersection anywhere, pass that upwards
PVS

17.  CurrentCluster = FindCluster(vPosCamera);

 TurnAllFacesOff();
 for(int i=0; i<NumVisibleLeaves; i++)
 {
 for(int f = 0; f < m_pLeaves[i].NumFaces; f++)
◦ TurnFaceOn(pLeafFaces);
 }
PVS

18. Radiosity

19. Radiosity

20.  Radiosity using PVS
◦ RADIOSITY (Tree)
 for(each leaf L in Tree)
◦ for(each light S in L)
 for(each leaf V that is in L’s PVS)
◦ Send S’s energy to the patches in V
Radiosity

21. Collision detection

22. Fake III

23. Q/A & IDEA