Movedefs.lua

Location

movedefs.lua is a file in the Gamedata/ directory of a Spring Game.

Purpose

This file defines MoveClasses which are used to determine pathing for units.

Source

The engine source code which parses the data from this file is viewable here: rts/Sim/MoveTypes/MoveInfo.cpp

Details

A mobile unit is assigned a MoveClass using the movementClass UnitDef tag. The engine determines the unit's pathfinding based on the properties of the MoveClass, so analogous properties (e.g. FootprintX) in the UnitDef should be the same for optimal behaviour.

All MoveClasses must belong to one of four possible types. A MoveClass is assigned a type simply by including it within the name string e.g. Tank_MyMoveClassName. Types are used in TypeMaps of Spring maps, which allow mappers to set per-type speed multipliers.

Types

• Bot - A ground based MoveClass. The default type if no matching type string is found.
• Tank - A ground based MoveClass. Identical to Bot other than interaction with TypeMaps.
• Ship or Boat - Are synonyms. All ships / boat MoveClasses must belong to this type to behave as ships.
• Hover - All hovercraft MoveClasses (traverse any depth of water without speed reduction) must belong to this class, as well as having canHover in their UnitDef to behave as hovers.

MoveClass Tags

string name  default: "" 

FIXME: The name of the MoveClass. Usually passed by the sub-table variable name rather than using the name tag (See #Example). Must contain "tank", "hover", "ship" or "boat" respectively for non-Bot types.

int footprintX  default: 1 

FIXME: How wide the MoveClass is in footprint units, left to right. 1 footprint unit = 16 elmos. Cannot be below 1. For mobile units this should be the same as the footprintX of its UnitDef.

int footprintZ  default: footprintX 

FIXME: How wide the MoveClass is in footprint units, top to bottom. 1 footprint unit = 16 elmos. Cannot be below 1. For mobile units this should be the same as the footprintZ of its UnitDef.

float crushStrength  default: 10.0 

FIXME: Power of a unit with this MoveClass to crush features and units. Any features (and units with crushing enabled via Spring.SetUnitBlocking) with a crushResistance less than this value will be crushed on contact (See Units-FeatureDefs#General and Units-UnitDefs#General).

float maxSlope  default: 60.0 (15.0 for hover types) 

FIXME: The maximum steepness of slope a unit with this MoveClass can climb. Spring doesn't calculate this in degrees, see #How_slope_is_determined.

float slopeMod  default: 4.0 / (maxSlope + 0.001) 

FIXME: How much a slope will slow a unit, 0 means no slowdown.

Heat Tags

These tags are used in unit avoidance.

• heatMapping - type: bool - default: false

This enables/disables generation and usage of path heats.

• heatMod - type: float - default: 0.05

The pathfinder cost modifier that is multiplied by the heat of the current square.

• heatProduced - type: int - default: 30

How much heat to place on a square if a path goes through it. heat set = max(currentSquareHeat, heatProduced).

Tank & Bot-Only Tags

• DepthMod
  • how much to slow down amphibian speed when they're underwater
• MaxWaterDepth

Ship-Only Tags

• MinWaterDepth
• SubMarine

Special notes

• depth is measured in elmos
• Slope is not measured in degrees.
• CrushStrength uses mass to determine if a feature can be crushed by a unit.
  • default feature: mass = metal * 0.4 + maxHealth * 0.1
  • default unit: mass = metalCost
• Slope/Depth mod
  • This value applies directly based on the slope/depth, meaning the deeper or higher the slope, the MORE it slows a unit down.

How slope is determined

Spring doesn't represent terrain slopes in degrees, internally it uses (1.0 - the terrain normal's y-component) so the slope of vertical faces is 1 and that of horizontal ones 0. A unit's maxSlope value (which is in degrees in its movedef) is converted so that the "can we go here?" (ie "maxSlope > terrainSlope?") comparisons are meaningful, the formula is 1.0 - cos(DEG2RAD(maxSlope * 1.5)). If you want to know the terrain angle in degrees, compute RAD2DEG(arccos(1.0 - terrainSlope)). For a bot with a maxSlope of 36 degrees (~0.41221 in "Spring format"), the maximum tolerable terrain angle is approximately

RAD2DEG(arccos(1.0 - 0.41221))

or 54 degrees. If maxSlope was 30, the MTTA would be 45, and if it was 60 (the highest sensible value due to that 1.5 scalar and the absence of overhanging cliffs) the bot could mount any terrain. In other words you do not need the long mathematical derivation, just remember that maxTerrainAngle = maxSlope * 1.5

--kloot, Thu Jul 31, 2008

Example

External Examples

'Balanced Annihilation' movedefs.lua

'Complete Annihilation' movedefs.lua

'Spring: 1944' movedefs.lua

'Spring Tutorial Game' movedefs.lua

'ZeroK' movedefs.lua