1. Terrain rendering in games
Matej Mlejnek
Institute of Computer Graphics and Algorithms
Vienna University of Technology
Vienna / Austria

2. Outline overview of terrain algorithms optimization criteria
Lindstrom algorithm
progressive meshes
ROAM
performance enhancements
games and engines

3. Overview of terrain algorithms (1)
grid vs TIN
w(v)=(x,y,z(x,y))
v=(x,y,z)

4. Overview of terrain algorithms (2)
discrete LOD
Continuous LOD
grid-based:
continuous LOD rendering by Lindstrom
Real-time Optimally Adapting Meshes (ROAM)
TIN-based
progressive meshes

5. Optimization criteria
time required to achieve a given triangle count
user specified view-dependent metrics
simplicity
strict frame rates
dynamic terrain
continuous changes
etc.

6. Continuous LOD by Lindstrom (1)
Quad tree
bottom-up
block-based vs. vertex-based

7. Progressive meshes PM representation
only single operation: merge (edge collapse) split (vertex split)
view-dependent PM

8. ROAM (1) triangle bintree top-down algorithm 2 priority queues: merge
split

9. ROAM (2) (mergeable) diamond forced split =>
no effort to avoid discontinuities

10. Comparison Lindstrom ROAM PM elementary operation
complex, 1 vertex reduction
basic, 1 vertex reduction
complex, 2 vertices reduction
triangles
rigth-isosceles
introduces slivers
complexity
O(mesh size)
O(triangle changes)

11. Performance enhancements
backface culling
object positioning
atmospheric obscurance
view frustum culling
progressive optimization

12. (Lindstrom algorithm)
Games and engines
NetImmerse
(progressive
meshes)
Tribes
(Lindstrom algorithm)

13. Results
Hoppe – progressive meshes

14. Thank you!
Matej Mlejnek