1. Terrain
Jyun-Ming Chen
Spring 2004

2. Issues Height field (design, Perlin noise) Frustum culling
Texturing (texgen, mipmap)
Transformation
LOD

3. Terrain Element
[i+1,j+1]
[i,j+1]
[i,j]
[i+1,j]

4. Terrain Design Height field Convert a gray scale image to terrain
Design naturally looking terrains with Perlin noise functions

5. Frustum Culling
Apply frustum culling to each terrain element to speed up rendering
Verify the improved frame rates

6. Frustum Culling (terrain version)
Test center point against frustum :
int SphereInFrustum (center, radius)
radius = w/sqrt(2)· w:width of terrain element
Quick break for terrain:
No need to test top and bottom

7. Applying Textures Mipmap is very important (esp. near horizon)
Use texgen facility to generate texture coordinates
procedural textures: fr08; Perlin2D

8. On Plane Equation of Texgen
[10,0,0,0]
[10,0,0,0], [1,0,0,0] and [0.1,0,0,0] are different
[1,0,0,0]

9. Texgen (cont) [0.1,0,0,0] From OpenGL APIDOC:
If the texture generation function is GL_OBJECT_LINEAR, the function , g = p1 * xo + p2 * yo + p3 * zo + p4 * wo is used

10. Vehicle on Terrain Determine the vehicle location [i,j]
Local y aligned with terrain normal
Local x modified to its projection on terrain plane
Z = X  Y
origin

11. Find Origin Z p2 X p0 p1

12. Level of Detail (LOD)
Without LOD, the polygons are crowded near horizon

13. LOD (cont)
In an ideally LOD’d scene, all polygons are roughly the same size in screen pixels.

14. ROAM (demo)