Simulation Landscape

[sholloway]

A simulation can have a landscape. A landscape serves the purpose of providing a "ground" surface for agents to traverse.

Landscape Characteristics.

• It has a gravity.
• It is composed of tiles.
• Tiles may be non-continuous. So there could be "islands" of tiles or tiles that are unreachable by direct traversal.
• Is defined in a scene file.
• Is responsible for the world coordinate system.
• A landscape may only have a single tile unit defined. Once this is defined all tiles are the same size.
• Defines a single origin for the world coordinate system (0,0,0).
• May have "holes" created by missing tiles.
• Adjacent tiles share vertices and edges.
• Could a tile have a state or reactive properties.

Tile Characteristics

• Has a fixed size.
• Is planner.
• Has a centroid which is at the center of surface defined by its vertices.
• Has an orientation around it's centroid.
• Composed of triangles.
• Can be different shapes. Square, Triangle, Hexagon.
• A tile may have neighbors.
• A tile can only have a single neighbor on a shared edge.
• A tile can be associated with a material or texture.
• Defined in 3 dimensional space.
• Has boundary vertices that define the shape of the tile.
• Has an inner tessellation.

Code Definition

@dataclass
class Landscape:
  """
  A static landscape could have it's own static spatial data structure for physics and path finding.
  """
  gravity: Newton
  tiles: Dict[Id, Tile]

@dataclass
class Tile:
  """
  Tiles should be immutable. 
  """
  id: Id                           # The unique identifier for this tile.
  material_id: Id           # Refers to which material or texture should be applied?
  vertices: List[Point]  # The list of points that define the shape of the tile.
  sides: int                   # number of sides this tile has. len(vertices)/2.

Landscape Builder

A GUI tool that aids in the landscape creation.

Area	Feature	Considerations
File Management	New Landscape	Launch from main menu.
File Management	Edit Landscape	Launch from main menu.
Format	Landscape File Format	Need a grammar and a parser.
Editing	Interactive Camera
Editing	Ambient Lightning	Shouldn't have to worry about lightning in the landscape editor.
Tiling	Add Tile	I'm thinking a of having a Tile Toolbar with toggle buttons. Add Square, Add Hex...
Tiling	Delete Tile	Need to ability to select a tile then do actions. Perhaps a right click context menu.

• Launch by Agent Playgroud -> File Menu -> Landscape -> New
• Launch by Agent Playgroud -> File Menu -> Landscape -> Open
• A landscape has it's own file format. A scene file can reference a landscape file.
• Note: The built in Python support for TOML doesn't provide the ability to write to a TOML file.
• Need good camera controls.
• Would it make more sense to create a Blender plugin or exporter?
• Should there just be a sim builder that enable creating landscapes or is it more flexible to build a landscape in isolation?
• The vertex normals should be "baked" by the Landscape editor. Every time a tile is added or removed the vertex normals should be recalculated for the relevant tiles.

General Tiling Considerations

• Grid parts and relationships
• Grid Edges
• Triangle Tiles have 12 Neighbors
• Square Tiles have 8 Neighbors
• Hexagon Tiles have 6 Neighbors
• Edges can be extruded up into tiles to form walls.

Square Tile Considerations

• Coordinate System
• Each edge can be labeled N, S, E, W
• Size: A tile a small unit of landscape. Picking the appropriate size for a sim is important. This should be sim independent.
  • Minecraft: 1 x1 m - A block is how large of a space a person can occupy. Produces blocky walls.
  • To get around the problem of representing walls, a lot of games just draw the walls thinner than the tiles they occupy. Walls are a full tile thick, they just don’t look like it.
  • Another approach is having multiple types of tiles. Floor tiles and wall tiles. Dwarf Fortress does this.
• I think having a tiling system that supports floor tiles and walls are extruded edges would be ok. Keep in mind I'm not trying to build a general purpose 3d modeler.

Hexagon Considerations and Resources

• Hexagonal Grids
• Hexagonal Grid Implementation Guide
• Wikipedia Hexmap

Landscape File Related Tasks

• [ ] Define a Landscape Grammar
• [ ] Write a Landscape file parser.
• [x] Write a Landscape file validator.
• [x] Parse a Landscape file into the CPU internal storage structure.
• [x] Error Conditions to detect/prevent.
  • [x] Multiple tiles may not have the same coordinate (x,y,z) location in Landscape space.

Rendering Landscape Tasks

• [x] Translate the Landscape CPU structure into Vertex and Index Buffers.
• [x] Tesselate the Landscape Tiles into triangles on the GPU using a Compute Shader.
• [x] Render the tessellated tiles with a vertex and fragment shader.
• [x] Set holistic tile size.

Tessallation Considerations

• GPU Tessellation with Compute Shaders Thesis
• Metal Compute Shader Tessellation Tutorial
• Using WebGPU Compute Shaders with Vertex Data
• Adaptive GPU Tessellation with Compute Shaders

Scene Tasks

• [x] Create a new Scene File Format
• [x] Define a Scene Grammar
• [x] Create a Scene File Validator
• [x] Create a Sim that loads a scene with a landscape composed of rectangular tiles.
• [ ] Create a Sim that loads a scene with a landscape composed of triangle tiles.
• [ ] Create a Sim that loads a scene with a landscape composed of hexagon tiles.
• [ ] Create a Landscape builder tool?

[sholloway]

Reusable Landscapes and Rapid Prototyping

I want Simulation scene files to reference a Landscape file. This is for the following reasons.

• Reduce the size and complexity of Simulation scene files.
• Enable reusing landscapes across multiple simulations.
• Enable a dedicated workflow for creating and editing landscapes.

JSON Landscape Files

TOML has proven to not be great for storing geometry information. I will leverage JSON for storing Landscape files for the following reasons.

• I can get started immediately and prove out the Landscape workflow.
• JSON is an open format that is machine agnostic.
• JSON is human readable.
• JSON Schema can be leveraged to define a contract for a valid landscape file.

The general process for loading a scene with a landscape file should be:

I want a progress loader that shows me an overall progress bar and that displays a message on what step we're on.

1. Parse the scene.toml file. If it has a reference for a landscape file, then proceed. Otherwise continue on with the scene parsing.
2. Load the JSON Schema.
3. Validate the Landscape File. If it is invalid display the error and stop. Don't crash the app.
4. If the landscape is valid, then parse the JSON into the intermediate format.
5. Tesselate the Landscape into a Triangle Mesh.
6. For the Triangle Mesh calculate face and vertex normals.
7. Continue on with the scene.