Math

Math #

Half-Life has a very limited number of entities to do math operations. They’re game_counter and game_counter_set. These entities are very limited by themselves, and Featureful SDK provides more powerful ways to do math operations.

Calc Ratio #

All entities have a calculable value associated with them - the concept borrowed from Spirit of Half-Life, where it’s called Calc Ratio (see also: Locus system). While most entities have a constant zero value as Calc Ratio, there’re few entities that implement this concept in Featureful SDK and might have a dynamic value:

  • game_counter - the Calc Ratio is the current counter value. Note that game_counter holds integer values only.
  • env_global - since each global has an integer number associated with them in Featureful SDK, the env_global can be used to access this number.
  • Monsters. For them Calc Ratio is the health / max health fraction (the the number in [0..1] range).
  • Wall rechargers (health and armor). For them Calc Ratio is the juice left / max juice capacity fraction (the the number in [0..1] range).
  • calc_ratio - Calc Ratio is calculated based on Calc Ratio of another entity.
  • calc_eval_number - calculate a number from two operands.
  • game_number - Calc Ratio is a stored floating point value.
  • player_calc_ratio - report some player related values like current health, armor and ammo.

Locus Ratio #

Locus Ratio (or LR for short) is a type of entity parameter. In FGD file they’re marked with [LR] suffix. LR parameter can be either a constant number or a name of another entity. In the latter case the Calc Ratio result of another entity will be used as a number. The entity that have LR parameters can behave differently depending on their values.

Some examples of entities having LR parameters:

  • trigger_push - can have a speed factor calculable from another entity.
  • env_shooter - can have a speed factor calculable from another entity.
  • calc_ratio - calculates its own Calc Ratio depending on LR parameter that could refer to another entity.
  • Vector related calc entities (e.g. calc_subvelocity) have LR parameter for factor.
  • calc_eval_number - calculate its own Calc Ratio depending on two LR parameters.
  • trigger_compare - when triggered, compares calculated values of two LR parameters and fire the targets accordingly to result.

Storing a value #

There’re few entities that can act as value storage for the result of calc_eval_number.

  • game_counter - the stored value will be cast to integer. The counter may fire its target and reset if it hit the limit.
  • game_number - the stored value will be preserved as is. This entity just stores the value and it’s expected to be accessed by other entities.
  • env_global with Modify/Set value trigger mode. The value will be cast to integer.