1. CSE 381 – Advanced Game Programming Terrain
Badlands, South Dakota

2. Think of it as a textured blanket

3. Obviously a rendering challenge Also a collision detection challenge
Terrain
Obviously a rendering challenge
Also a collision detection challenge
Requires a huge amount of data for outside game environments
Usually pre-lit – what does this mean?
Typically integrated with:
sky
water
sun

4. Terrain Characteristics
fidelity
how realistic is it?
for model & textures
spread
degree to which areas of the terrain are unique
freedom
how much are the player’s movements restricted by the terrain?
Want real earth terrain data?

5. Some game engines have terrain managers
Terrain Modeling
Some game engines have terrain managers
with their own GUI terrain generation tools
with their own rendering optimizations
Terrain building as models
can also be positioned, rotated, etc. as one

6. Texturing provides this Typical textures:
Terrain Cover
Texturing provides this
Typical textures:
grass, flowers, dirt, pebbles, rocks, moss, sand, stone, etc.
Most engines support terrain texture blending
What’s that?
good for transition areas at borders of differing terrain

7. When making Terrain Textures
avoid making distinctive marks
Why?
avoid making textures with patterns
Remember, these will be repeated over an area

8. How do you think terrain data is stored?
Height maps
What’s that?
a 2D image that stores topographical info for a square map region
different shades of gray represent different elevations
brightness of a pixel denotes its elevation

9. Each pixel represents an area’s elevation
More on height maps
Each pixel represents an area’s elevation
ex: 1 pixel is a square meter
black may be the base elevation
pure white may be the other extreme
values in between are scaled
Ex: 8 bits per pixel means 256 possible elevations

10. Each pixel represents a tile (square of terrain) For each tile
Using Height Maps
Terrain generator reads a height map file and creates the appropriate geometry
How?
Each pixel represents a tile (square of terrain)
For each tile
a vertex is generated at appropriate elevation
two triangles are generated connecting new vertex to bordering vertices
Some generators will add more vertices
Why?
Interpolation (more on this later)

11. Terrain Units WU – world units Example:
refers to measurement scale for a game world
basic WU is one inch
Example:
level tile is 10 X 10 units (meters or otherwise)
100 tiles X 100 tiles
level is 1000 X 1000
NOTE: each tile may have many triangles
again, depending on interpolation

12. Think of as its own level object Has a position, scale, rotation
Water
Think of as its own level object
Has a position, scale, rotation
Typically specified using a single rectangle
can fit into non rectangular terrain contours
For camera out of water:
typically water drawn using multiple textures
one for shallows, one for deep
can be blended via depth gradient
effects then applied
E.g., specular highlights
For camera under water:
other effects like fog, viscosity, waves, etc.

13. Terrain Rendering What do we need to know? how to store the data
how to load it
how to render it
how to detect collisions with it. Why?
Nothing should go below the terrain

14. Height Maps Revisited Height maps are images
When a level is loaded, how might we store terrain data such that it can be efficiently:
rendered
used in collision detection calculations

15. 2 Terrain Management Options
Static Option - Load height map into a mesh (or meshes) and treat terrain as any other mesh
easy to implement
typically divided into clumps
Dynamic Option - Load height map data into data structure, each frame, use dynamically changing mesh based on location of frustum
that’s a bit trickier

16. Clumps What’s a clump? What’s the benefit of managing clumps? Why?
a chunk of terrain
subset of a level’s full terrain
What’s the benefit of managing clumps?
more efficient rendering/management of terrain
Why?
problem reduction

17. Clump Construction Example
Suppose we are loading a 256 x 256 height map
Construct terrain as 16 x 16 clumps
How many clumps is that?
256
How many vertices per height map pixels?
depends on interpolation (more on this in a moment)

18. How do we use the clumps?
Each frame, select only the visible clumps for rendering
How do we do that?
frustum culling is one way
but there’s a simpler way
clumps are cells in the 2D grid
in what cell is the camera?
render that clump
in which direction is the look at vector?
render those clumps
know the max clump distance that can be viewed

19. Dynamic Terrain Generation
Height map is a 2D grid
At start of level:
build a recyclable mesh to store dynamic terrain
Each frame:
determine where on the grid the camera is
fill dynamic terrain with visible portions of grid

20. What’s the point of interpolation?
Rounding terrain
How?
add more vertices to the grid
Simple algorithm
add 2 between each pair of vertices
what height?
make them closer to nearest existing vertex than 1/3 of height difference. Why?