Scene modeling, Mazes, and Terrain

CSE 3541Matt Boggus

Overview

• Hierarchical scene modeling and Parenting in Unity

• Mazes

• Terrain

Sample Scene

Hierarchical scene – chair 1

Hierarchical scene – chair 2

Hierarchical scene – chessboard

White chess pieces – child of chessboard

Rook piece – child of white chess pieces

Unity Parenting

• Video tutorial (parenting in the GUI)

• Transform.parent scripting reference

• ParentingExample.unitypackage

Mazes

Maze from Image-guided maze construction, Xu and Kaplan 2007, Siggraph

Maze tiles from OSU research

Simple mazes – binary grid

• Matrix of booleans• ex: 21 x 21

• Arbitrary mapping:– True = black pixel = wall– False = white pixel =

open space

Creating the scene

Foreach (i,j) in boolean[x,y] mazeif(maze[i,j])

Create Cube at position (i,0,j)

Creating GameObjects

for(int i = 0; i < numberOfAsteroids; i++){ GameObject aSphere = GameObject.CreatePrimitive(PrimitiveType.Sphere); aSphere.transform.parent = transform; aSphere.name = "sphere" + i.ToString();

aSphere.transform.position = new Vector3(Random.Range(-10.0f, 10.0f), Random.Range(-10.0f, 10.0f),

Random.Range(-10.0f, 10.0f));

aSphere.transform.localScale = new Vector3(Random.Range(0.0f, 1.0f), Random.Range(0.0f, 1.0f),

Random.Range(0.0f, 1.0f));}

Deleting GameObjects

GameObject myObject;// do stuff with myObject (create, animate, etc.)Destroy(myObject);/* Note: myObject still exists as a variable name, only the corresponding GameObject in the scene is removed */

Procedural maze initial values

All open space – add walls All walls – add open space

Checking for a solution – Flood-fill

• Determine the area connected to a given node in a multi-dimensional array

• Applications:– “Paintbucket” tool– Connected components– Pathfinding

Animation fromhttp://en.wikipedia.org/wiki/Flood_fill

Recursive flood-fill codeFlood-fill (x, y, value, grid) { if(x < 0 || y < 0 || x >= XSIZE || y >= YSIZE) return; if(grid[x,y] == -1 || grid[x,y] == value) return;

grid[x,y] = value; Flood-fill(x-1,y, value, grid); Flood-fill(x+1,y, value, grid); Flood-fill(x,y+1, value, grid); Flood-fill(x,y-1, value, grid);}

Note: method is prone to stack overflow

Iterative flood-fill algorithmFlood-fill (x, y, value, grid) { Set Q to the empty queue Add position(x,y) to Q While Q is not empty { Dequeue position p if (p.x or p.y out of bounds) continue; if (grid[p.x,p.y] == -1 || grid[p.x,p.y] == value) continue; grid[p.x,p.y] = value; Enqueue (p.x-1,p.y); Enqueue (p.x+1,p.y); Enqueue (p.x,p.y-1); Enqueue (p.x,p.y+1); }

Terrain

http://accad.osu.edu/researchmain/gallery/project_gallery/iires-project.html

Heightfield definition

• Function u(x,y) gives height at (x,y)• Store height values in an array u[x,y]• Note: limited to one height per (x,y)

Heightfield smoothing

• For every grid cell u[i,j], set it to average of itself and neighbors

• Critical thinking – implementation concerns:– A. looping order– B. boundary cases– C. both– D. none

For more terrain creation and editing operations, see http://www.lighthouse3d.com/opengl/terrain

Heightfield mesh creation

u[x,y] ; dimensions n by n

Heightfield mesh creation (clockwise winding order)

Quad[0,0] Vertices are U[0,0], U[0,1], U[1,1], U[1,0]Quad[i,j] Vertices are U[i,j], U[i,j+1], U[i+1,j+1], U[i+1,j]

Heightfield creation (iteration)

Inner loop iterates over i, the x coordinate Last quad: i=5(i = n-1)

Heightfield creation (iteration)

Outer loop iterates over j, the z coordinateLast row: j=5 (j = n-1)

Unity terrain engine

• Terrain object http://docs.unity3d.com/ScriptReference/Terrain.html

• Terrain object has a field terrainData http://docs.unity3d.com/ScriptReference/TerrainData.html – terrainData has methods getHeight http://

docs.unity3d.com/ScriptReference/TerrainData.GetHeights.html

– terrainData has methods setHeights http://docs.unity3d.com/ScriptReference/TerrainData.SetHeights.html

• Video tutorial on runtime terrain modification https://www.youtube.com/watch?v=YRQur24S0BY