FOV

Field of view algorithm enumeration.

Overview

FOV is an IntEnum that specifies which algorithm to use when computing field of view on a Grid. Different algorithms offer trade-offs between performance, accuracy, and visual characteristics. The algorithms are provided by libtcod.

Quick Reference

# Set FOV algorithm on grid
grid.fov = mcrfpy.FOV.SHADOW

# Compute FOV from a tile position (accepts a tuple or Vector)
grid.compute_fov(player.grid_pos, radius=8)

# Check visibility
if grid.is_in_fov(target_x, target_y):
    print("Target is visible!")

# Available algorithms
mcrfpy.FOV.BASIC
mcrfpy.FOV.DIAMOND
mcrfpy.FOV.SHADOW
mcrfpy.FOV.PERMISSIVE_0  # through PERMISSIVE_8
mcrfpy.FOV.RESTRICTIVE
mcrfpy.FOV.SYMMETRIC_SHADOWCAST

Constructor

FOV is an IntEnum and its values are accessed as class attributes.

algorithm = mcrfpy.FOV.SHADOW

Values

Value	Description
`BASIC`	Basic raycasting algorithm. Fast but can miss corners.
`DIAMOND`	Diamond-shaped FOV. Symmetric and predictable.
`SHADOW`	Shadow casting algorithm. Most commonly used, good balance.
`PERMISSIVE_0`	Permissive FOV, strictest. Narrowest field of view.
`PERMISSIVE_1`	Permissive FOV level 1
`PERMISSIVE_2`	Permissive FOV level 2
`PERMISSIVE_3`	Permissive FOV level 3
`PERMISSIVE_4`	Permissive FOV level 4 (middle)
`PERMISSIVE_5`	Permissive FOV level 5
`PERMISSIVE_6`	Permissive FOV level 6
`PERMISSIVE_7`	Permissive FOV level 7
`PERMISSIVE_8`	Permissive FOV, most permissive. Widest field of view.
`RESTRICTIVE`	Restrictive precise permissive FOV.
`SYMMETRIC_SHADOWCAST`	Symmetric shadowcasting algorithm.

Note: the enum members are BASIC, DIAMOND, SHADOW, etc. — not FOV_BASIC and friends (that naming is the underlying libtcod C constant, not the Python attribute).

Algorithm Comparison

BASIC

Simple raycasting from the viewer to each cell. Fast computation but can produce asymmetric results where the player can see a cell but an enemy at that cell cannot see the player.

DIAMOND

Creates a diamond-shaped visible area. Produces symmetric results and is easy to understand, but may not look as natural as shadow casting.

SHADOW (Recommended)

The most popular algorithm for roguelikes. Casts shadows from obstacles to determine visibility. Produces natural-looking results with good performance. This is the default choice for most games.

PERMISSIVE_0 through PERMISSIVE_8

A family of algorithms that vary in how “permissive” they are about visibility around corners. Lower numbers (0-3) are stricter and show less around corners. Higher numbers (5-8) are more permissive and reveal more. Level 4 is the middle ground.

Usage Patterns

Basic FOV Setup

import mcrfpy

scene = mcrfpy.Scene("fov-demo")
mcrfpy.current_scene = scene

# Create grid and set algorithm
grid = mcrfpy.Grid(grid_size=(80, 45), texture=mcrfpy.default_texture, pos=(0, 0), size=(800, 450))
grid.fov = mcrfpy.FOV.SHADOW
grid.fov_radius = 10
scene.children.append(grid)

player = mcrfpy.Entity(grid_pos=(5, 5), texture=mcrfpy.default_texture, sprite_index=84)
grid.entities.append(player)

enemies = [mcrfpy.Entity(grid_pos=(10, 10), texture=mcrfpy.default_texture, sprite_index=85)]
for enemy in enemies:
    grid.entities.append(enemy)

# Compute FOV from the player's tile position (radius defaults to 0 = unlimited when omitted)
grid.compute_fov(player.grid_pos)

# Use in visibility checks
for enemy in enemies:
    if grid.is_in_fov(enemy.grid_x, enemy.grid_y):
        enemy.visible = True

FOV with Color Layer

ColorLayer.draw_fov() computes FOV internally and paints the layer in one call — no separate grid.compute_fov() step is needed for this pattern:

fog = mcrfpy.ColorLayer(z_index=10, name="fog")
grid.add_layer(fog)
fog.fill(mcrfpy.Color(0, 0, 0, 255))  # Start dark

def update_visibility():
    fog.draw_fov((player.grid_x, player.grid_y), radius=8)  # Reveal visible cells, re-fog the rest

Algorithm Selection

# For classic roguelike feel
grid.fov = mcrfpy.FOV.SHADOW

# For tactical games where seeing around corners matters
grid.fov = mcrfpy.FOV.PERMISSIVE_6

# For symmetric stealth games
grid.fov = mcrfpy.FOV.DIAMOND

# For fast computation in large maps
grid.fov = mcrfpy.FOV.BASIC

Dynamic Algorithm Switching

# Different FOV for different game modes
def set_stealth_mode():
    grid.fov = mcrfpy.FOV.PERMISSIVE_2  # Limited vision
    grid.fov_radius = 5

def set_alert_mode():
    grid.fov = mcrfpy.FOV.SHADOW
    grid.fov_radius = 12

FOV