Fulgur.
Procedural lightning.

Quick start

1. Enable Fulgur Lightning in Edit > Plugins and restart the editor.
2. Open the sample level /Fulgur/Maps/Fulgur_Showcase (Content Browser > Plugins > Fulgur Content > Maps). It has 20 numbered booths, each showing one feature with its settings written on the wall.
3. Turn on Realtime in the viewport (Ctrl+R) to see the bolts move in the editor. Press Play to see the interactive booths: the moving target, the spinning panel, and Tesla arcs that leap onto you.
4. To add lightning to your own level, search Fulgur in Place Actors.

Actors

Each actor carries up to 4 real point lights. They are stretched along the bolt, follow its brightness, and light and shadow the set. Their settings are under Fulgur > Light: intensity in candelas, color, radius, shadows, and Light Lift to raise them off a floor.

Bolt presets

Main settings

All actors share the settings of the Fulgur Lightning component.

Shape

• Displacement: amplitude of the wander, as a fraction of the bolt length.
• Kinks: the big breaks.
• Roughness: mid-scale detail.
• Curviness: 0 gives straight segments, 1 gives waves.
• Crinkle: pixel-scale jaggedness.
• Strands and Strand Spread: braided strands.
• Branch Depth, Branch Density, Branch Length, Branch Angle and Branch Bias (for example, make branches fall toward the ground).
• Flatten: presses the arc against a surface.

Look

• Core, Glow and Haze colors.
• Core Width. A filament is never drawn thinner than Min Pixel Width on screen: thinner filaments get dimmer instead, so they never shimmer.
• Glow Width: the tight halo.
• Haze Width: the wide veil.
• Brightness for each layer.
• Hot Spots: bright beads along the filament.
• Flare Size: the impact point.

Motion

• Shape Rate: how often the fine detail renews. 24 gives a new shape every frame.
• Swim Rate: speed of the large-scale shape.
• Smoothness: 0 makes the arc jump, 1 makes it morph.
• Flicker.
• Branch Rate and Branch Flicker.
• Pulse Rate: energy pulses running along the arc.

Sparks

• Ballistic sparks: gravity, drag, bounce on the impact surface, cooling from blue-white to orange.

Strike (Bolt in Strike mode, Storm)

• Interval, First Strike, Jitter, Leader Time, Decay, Restrikes.
• Or Times, an exact list of flash times.

Bolt brightness does not depend on the scene's exposure, so a preset looks the same in any level. The lights are physical (candelas): tune them to your exposure.

Sequencer and Movie Render Queue

By default every actor follows the world clock. That is live in the editor viewport (Realtime) and in game.

For cinematics, tick Use Custom Time on each Fulgur actor and key Custom Time linearly on the sequence time (0 s at the first frame). The plugin ships a Python script that does this for every Fulgur actor of the open sequence:

1. Open your sequence in Sequencer.
2. Run Tools > Execute Python Script and pick Plugins/Fulgur/Content/Python/key_fulgur_time.py. This needs the Python Editor Script Plugin, which is on by default.

After that:

• scrubbing shows the right frame;
• MRQ renders the same image every time;
• temporal sub-samples get in-between shapes, which gives a natural motion blur on crackling arcs.

Time Scale and Time Offset slow down, speed up or shift each actor.

Bloom: Unreal's default bloom at 0.7 to 1 works well. The glow and haze are already drawn by the plugin.

Performance

• Geometry is built on the CPU for every view. A typical bolt costs a few thousand vertices.
• Longer bolts and a smaller Segment Length give more vertices. Long beams of 10 m or more read well with a Segment Length of 3 to 5 cm.
• The point lights cost more than the geometry, especially with shadows. Lower Light Count, untick Light Shadows, or untick Cast Light on bolts that only need to glow.

Compatibility

• Unreal Engine 5.4, 5.5, 5.6 and 5.7, Windows. Runtime module: works in packaged games.
• Deferred and forward renderers, Lumen or not.
• The material is translucent additive, so it is not visible in Lumen reflections. The point lights are.
• Not network replicated: bolts are cosmetic. Drive them from your own replicated gameplay state.