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Vision System

How Mimir implements D&D 5e vision and lighting rules.

Why Vision Matters

In D&D, what characters can see affects:

  • Exploration and discovery
  • Combat tactics
  • Stealth and surprise
  • Atmosphere and tension

Mimir’s vision system brings these rules to your virtual tabletop.

D&D 5e Vision Rules

Light Levels

D&D defines three light levels:

Bright Light Most creatures see normally. Includes:

  • Daylight
  • Torchlit rooms
  • Magical light

Dim Light Lightly obscured area. Creates:

  • Disadvantage on Perception checks
  • Shadows and half-light

Darkness Heavily obscured area. Results in:

  • Effectively blind
  • Auto-fail sight-based checks
  • Advantage for hidden creatures

Darkvision

Many races and creatures can see in darkness:

  • Treat darkness as dim light
  • Treat dim light as bright light
  • Cannot discern color (shades of gray)
  • Typical range: 60 feet

How Mimir Implements This

Fog of War

The map is divided into:

  • Revealed - Areas PCs can see
  • Hidden - Areas beyond PC vision

As tokens move, fog updates automatically.

Vision Radius

Each PC token calculates visible area:

  1. Base vision from ambient light
  2. Extended by darkvision (if applicable)
  3. Extended by light sources
  4. Blocked by walls (UVTT maps)

Light Sources

Placed light sources create illumination:

  • Torch: 20 ft bright, 40 ft dim
  • Lantern: 30 ft bright, 60 ft dim
  • Candle: 5 ft bright, 10 ft dim

Lit sources expand visible areas. Unlit sources have no effect.

Wall Occlusion

UVTT maps include wall data:

  • Vision stops at walls
  • Rooms reveal individually
  • Doors can be open or closed

Without wall data, vision is circular (line of sight to all directions).

Vision Modes

Fog Mode

Default exploration mode:

  • Map hidden outside vision
  • Reveals as PCs explore
  • Maximum immersion

Token Mode

Combat-focused mode:

  • Map fully visible
  • Enemy tokens hidden outside vision
  • Geography known, enemies hidden

Reveal Mode

Override mode:

  • Everything visible
  • Bypasses all fog
  • Use for non-exploration scenes

What Creates Vision

Does reveal fog:

  • Player Character tokens
  • Active light sources

Does not reveal fog:

  • NPC tokens
  • Monster tokens
  • Hidden tokens

This prevents accidental reveals from positioned enemies.

Practical Considerations

Dungeon Exploration

  • Use Fog mode
  • Set ambient light to dim or dark
  • Place torches on walls
  • Reveal room by room

Combat Encounters

  • Consider Token mode
  • Players see the battlefield
  • Hidden reinforcements stay hidden

Town Scenes

  • Use Reveal mode
  • Fog doesn’t fit the fiction
  • Focus on roleplay, not exploration

Dramatic Reveals

  • Use Blackout
  • Position elements
  • Reveal with effect

Tips for DMs

Before Sessions

  • Check ambient light setting
  • Place light sources strategically
  • Test with a PC token

During Play

  • Toggle lights for effect
  • Adjust ambient as needed
  • Switch modes as appropriate

For Atmosphere

  • Dark + scattered torches = tension
  • Bright = safety
  • Sudden darkness = danger

See Also