Flowmap Painter

Module: Art · Category: Paint · Tool ID: FlowmapPainter

Paint direction, not colour. Drag across a mesh in the viewport and the tool records the direction of each stroke into a UV-space vector field, then bakes it to a flowmap texture your materials can advect with — water flowing round a rock, wind combing through foliage, a cape settling in a direction, flame tips licking upward.

Painting happens on the actual mesh in the level, so what you paint is what the surface gets, without round-tripping through a 2D package and guessing at the UV layout.

Flowmap Painter mid-session: Status showing painting active with the hovered UV and dab count, Brush settings, the Export section with format and resolution, and Session save/load.

When to use it

• Water flow around obstacles, down a riverbed, or through a channel
• Wind direction through foliage and grass cards
• Fabric: capes, banners, cloth that should read as draping in a direction
• Hair and fur direction
• Fire and smoke, where flame tips need to lick a particular way
• Anywhere a material advects a texture and the direction must follow the surface

What it isn’t for

• Don’t use it to author a flowmap for a mesh you don’t have in the level. Painting is viewport-based and needs a selected Static Mesh actor.
• Don’t use it where a procedural flow field would do. For water surfaces driven by simulation, Fluid Lab generates flow directly.

Opening the tool

1. Open the EQLabs Hub and search for flowmap or flow (or browse to Art → Paint).
2. Click the tool card.
3. Select a Static Mesh actor in the level.
4. Click Begin Painting, then LMB-drag across the mesh.

Almost every control is gated on an active session. Without one the tool tells you plainly — “Click Begin Painting first” — rather than appearing to work.

If you click Begin Painting with nothing suitable selected: “No Static Mesh actor selected — pick one in the level and click Begin Painting again.”

Status

The Status block is the feedback loop while painting.

Readout	Meaning
Painting mode	Active / Inactive
Target mesh	The mesh being painted, or a prompt to select one
Hover UV	UV coordinate under the cursor
Dabs this stroke	How many dabs the current stroke has laid down

Hover UV is the one to watch. It tells you where on the texture you are actually painting, which is how you catch a mesh whose UVs overlap or are laid out differently than you assumed — the flowmap will have those same overlaps.

Painting

Hold LMB on the mesh and drag. The drag direction sets the flow direction; the cursor circle shows the brush footprint.

Control	Notes
Begin Painting	Starts a session on the selected Static Mesh actor
End Painting	Ends the session

A stroke painted directly onto the mesh in the viewport, the flow written where the brush passed.

Brush

Setting	Range	Notes
Radius (UV)	0.001 – 0.5	Brush radius in UV space, not world space
Falloff	—	Edge softness of the dab
Strength	—	How strongly each dab overwrites existing flow
Erase mode	—	Removes flow instead of adding it

Radius is UV-space, which is why the same brush covers a different amount of surface on differently-scaled UV islands. If the brush feels enormous on one part of a mesh and tiny on another, the mesh has non-uniform texel density — worth checking with UV & Texel Suite.

The panel while painting: brush radius, falloff and strength, smoothing, and the export block with resolution, format and output folder.

Presets

Six curated brush configurations tuned for common workflows:

Preset	For
Stream	River-like flow
Vortex	Eddies and swirls
River Bend	Wide curves
Wind Sweep	Broad airflow
Cape Drop	Fabric drape
Fire Lick	Sharp flame tips

Presets overwrite Radius, Falloff and Strength. Erase mode stays as you left it — so applying a preset mid-erase does not silently put you back into painting.

Presets need an active session: they push values into the running session’s brush.

Smoothing and clearing

Control	Notes
Smooth iterations	How many 3×3 Gaussian relaxation passes per Smooth click
Smooth	Applies the relaxation
Clear Flow Field	Wipes the field

Smoothing is the difference between a hand-painted field and one that reads as a coherent current. Hard direction changes between adjacent dabs produce visible tearing when a material advects along them; a couple of relaxation passes resolve it. Over-smoothing flattens the field toward uniform, so work in small increments and look at the result.

Export

Setting	Notes
Resolution	Output texture resolution
Format	RGBA8 (recommended), RGBA16F (high precision), or RGBA8 (mobile fallback) — all uncompressed linear
Output folder	Long-package path, e.g. /Game/EQLabs/Flowmaps
Texture name	Defaults to T_Flowmap_<MeshName>
Also create sample material	Generates a paired M_FlowmapSample_<Name> with the flowmap pre-bound
Export Flowmap	Bakes the field to a UTexture2D

Choosing a format

Format	Use when
RGBA8 (recommended)	The default. Uncompressed linear — correct for nearly all work
RGBA16F (high precision)	Authoring at very high precision, or when 8-bit banding shows in long advection
RGBA8 (mobile fallback)	Mobile targets

On BC5. BC5 is the canonical flowmap format in general, and in v2.0.2 the export button’s tooltip still describes the options as “BC5 / R16G16 / R8G8”. On UE 5.4 that is not what ships: BC5 compression requires the Normal-Map semantic tag (TC_BC5 came later), so the slot exports as uncompressed RGBA8 — the same disk layout as R8G8 but correctly tagged as linear colour. The tooltip is corrected in the next release; the dropdown labels were always accurate.

If you need real BC5 compression in production, export as normal and then set the texture asset’s Compression Settings to Normalmap in the Content Browser.

Also create sample material is worth using on a first export — it gives you a material with the flowmap already wired, so you can see the flow working before integrating it into a real shader.

Sessions

Work in progress can be saved as a UFlowmapPaintSession asset, carrying the flow field and the brush settings.

Control	Notes
Save Session…	Saves the in-progress field + brush settings
Load Session…	Restores a saved session

Both require an active session. Sessions are how you leave a complex flowmap half-finished and come back to it — the exported texture is the output, but the session is the editable source.

Treat the session as the master. The baked texture cannot be meaningfully re-edited; the session can.

Workflow: flow around a river rock

1. Select the rock in the level → Begin Painting.
2. Apply the Stream preset.
3. Drag along the water’s path, following the surface around the rock.
4. Switch to Vortex and add eddies behind it.
5. Smooth once or twice to remove tearing between strokes.
6. Save Session… before exporting.
7. Set format BC5, tick Also create sample material, Export Flowmap.
8. Check the sample material, then wire the texture into the real shader.

Tips and gotchas

• Everything needs an active session. Presets, Smooth, Clear, Save all refuse without one and say so.
• Radius is UV-space. Uneven texel density makes the brush change apparent size across the mesh.
• Watch Hover UV to catch overlapping UVs. Painting one island paints its overlapping twin too.
• Smooth in small steps. Relaxation is cumulative and over-smoothing flattens the field.
• In v2.0.2 the export tooltip names BC5/R16G16/R8G8 while the dropdown offers RGBA8/RGBA16F/RGBA8. Trust the dropdown — on 5.4 the “BC5” slot ships uncompressed. Set Compression Settings to Normalmap afterwards if you need real BC5. The tooltip is corrected in the next release.
• Save the session, not just the texture. The texture is not re-editable.
• Erase mode persists across preset changes, by design. Check it if painting seems to remove flow.

Related tools

• Flow Map Studio — generation and inspection of flow maps, where this is hand authoring
• Fluid Lab — simulation-driven flow for water surfaces and rivers
• Layered Texture Paint Suite — the other viewport painting tool
• UV & Texel Suite — diagnose the UV density that makes a UV-space brush behave unevenly