What is an Emissive Map? (Glow Effects in Game Assets)
Emissive maps control which parts of a surface emit light regardless of scene lighting. Glowing screens, lava cracks, LED strips, neon signs — any surface that appears to produce its own light needs an emissive map. This guide explains how they work and how to paint them correctly.
What is an Emissive Map?
An emissive map defines areas of a surface that appear to emit light. Unlike every other PBR channel — which responds to scene lighting — emissive areas display their color at full brightness no matter how dark the environment is. In a pitch-black room, an emissive surface still glows.
The emissive map is an RGB texture where the color of each pixel determines the color and brightness of the glow. Black means no emission. Any non-black value produces emission in that color — a cyan pixel makes a cyan glow, an orange pixel makes an orange glow.
How Emissive Works in PBR
In a standard PBR material, the final pixel color is calculated by combining your albedo, roughness, and metallic values with the scene's lighting. The emissive channel sits outside that calculation entirely — it's simply added on top of the lit result.
This additive nature is important. An emissive value of (1, 1, 1) — pure white — added over a black albedo surface makes that surface appear white regardless of scene lighting. An emissive value of (0.5, 0.8, 1.0) — light blue — makes the surface appear to glow blue. The albedo color underneath is still there, but the emissive addition dominates.
No emissive
Surface responds normally to scene lighting. In a dark room it appears dark. In bright light it shows the albedo color. Behaves like a regular physical surface.
With emissive
Emissive areas ignore scene lighting entirely. They appear at their painted brightness in any lighting condition — bright in darkness, still visible even when all lights are off.
Emissive values can exceed 1.0 — moving into HDR (High Dynamic Range) territory. Values above 1.0 are what trigger the Bloom post-processing effect in most engines, creating the characteristic light-bleed halo around very bright surfaces.
Emissive and Bloom
Bloom is a post-processing effect that causes very bright pixels to bleed light into surrounding pixels — simulating how cameras and human eyes respond to intense light sources. It's what gives neon signs their characteristic soft halo and makes lava look genuinely hot.
Bloom kicks in when emissive values push into HDR range — above 1.0. The higher the value, the more intense and wide-spreading the bloom halo becomes. Getting this range right is what separates a convincing glow from an effect that looks overblown or flat.
| Emissive Intensity | Visual Result | Typical Use |
|---|---|---|
| 0.1 – 0.9 | Glows in darkness, no bloom halo | Dim indicator lights, subtle backlit screens, faint bioluminescence |
| 1.0 – 3.0 | Bright glow with a soft bloom halo | Neon signs, monitor screens, LED strips, fire embers |
| 3.0 – 10.0 | Intense bloom, strong light bleed into surroundings | Lava, welding arcs, explosions, energy weapons |
| 10.0+ | Extreme bloom — almost blinding | Sun surfaces, nuclear effects, extreme sci-fi energy cores |
Painting Emissive Maps
The key principle when painting an emissive map is mask first, color second. Start with a completely black canvas — meaning no emission anywhere. Then paint only the areas that should actually glow.
Start with black everywhere
Fill the emissive channel with pure black (0, 0, 0). This is the baseline — no emission on any surface. Every non-black pixel you paint from here will produce a glow.
Identify your emissive areas
Look at your albedo map and decide which elements actually emit light — screens, bulbs, indicator lights, lava cracks, energy conduits. Only those areas get painted.
Paint the glow color
Paint those areas with the color they should glow. Match the hue to your albedo where it makes sense — a cyan screen glows cyan, orange lava glows orange. Keep edges sharp — emissive bleeding is handled by Bloom in-engine, not by soft brush edges in the map.
Set intensity in the material
In your engine's material, multiply the emissive texture by an intensity value. This is how you push into HDR range for Bloom without repainting the texture — change the multiplier in the material instead.
Common Use Cases
Almost every game genre has assets that benefit from emissive maps. Here are the most common situations where artists reach for the emissive channel.
Computer monitors, holograms, futuristic dashboards, status panels. The screen area is emissive; the bezel and casing are black in the emissive map.
Rock surfaces with glowing crack lines in orange-red. High emissive intensity drives bloom to sell the heat. One of the most striking uses of the channel.
Bulb surfaces, fluorescent tube faces, LED strip surfaces on props. Makes the light source itself appear lit even when the prop is in shadow.
Energy conduits, weapon charge indicators, power cores, reactor panels. Cyan and blue emissive is a staple of the sci-fi art direction vocabulary.
Glowing mushrooms, luminescent plants, alien creatures, deep-sea life. Soft, low-intensity emissive in greens and blues creates convincing organic glow.
Warning lights, power LEDs, status readouts on machinery. Often animated at runtime via material parameters — the emissive map masks where the light appears.
Emissive masks vs full RGB maps
There are two approaches to emissive maps. A full RGB map paints both the location and the color of the emission into one texture. A greyscale mask defines only where emission happens — the actual color is set as a material parameter at runtime.
The mask approach is more flexible: you can change the emissive color without touching the texture. This is useful for assets that need to display different status colors — a red alert state vs a green standby state — driven by game logic rather than a new texture per state.
Painting Emissive in Trumble
Trumble includes an Emissive channel alongside Albedo, Roughness, Metallic, and Normal in its PBR painter. Switch to the Emissive channel in the layer panel, and paint directly onto the mesh. The 3D viewport shows a real-time preview of how the emissive areas read against the rest of the material.
The most reliable workflow is to paint your Albedo first, then switch to Emissive and use the Albedo as your visual guide. The areas that should glow in the emissive map correspond directly to the screen, light, or lava sections you already painted in the albedo — the two maps work together to make the material read correctly in-engine.
Select the Emissive layer in Trumble's channel panel. Paint black as the base, then add glow color only to the areas that should emit light.
Trumble's 3D viewport shows emissive contribution in real time. Check that glow areas align correctly with the albedo features underneath.
The emissive map is included automatically in Trumble's engine export packs — named and formatted correctly for Unreal, Unity, or Godot.