Virtual Shadow Maps and decal components both fall apart at scale: VSMs pay an enormous GPU and CPU culling cost past a few hundred movers, and one decal per unit means one draw call per unit — your RTS army, your horde wave, your projectile swarm drowns the renderer before it drowns the player.

Material-Driven Shadows takes the opposite approach. Every shadow that shares a mesh and a material lives in one instanced static mesh component, and the projection itself is material math rather than rasterisation: the CPU writes a single transform plus four custom-data floats per unit, and the vertex and pixel shaders do the rest — sliding the shadow along the light direction as a unit jumps, stretching it as the sun drops towards the horizon, and blending it softly into hills and stairs with a depth fade instead of per-frame ground traces.

Drop the component on your unit Blueprint, press Play, and the whole army costs one draw call. The included demo map measures 1,101 shadow casters in 1 draw call at 0.91 ms of total subsystem CPU time.

KEY FEATURES

• One draw call per mesh/material pair — not per unit. 100 units or 10,000 units cost the same number of draw calls, and GetNumBatches() tells you exactly what that number is.

• The projection lives in the material. Per-instance custom data carries radius, opacity, height above ground and light-stretch to the GPU. Rotating your day/night sun re-stretches every shadow in the world in the vertex shader, at zero extra CPU cost.

• Jump and fly handling out of the box — shadows slide away from an airborne unit and fade out as it climbs, driven by two tunable heights per component.

• Slope fitting without CPU traces: a depth-fade blend makes the flat quad hug hills, ramps and stairs instead of clipping through them.

• Bounded ground-trace cost. Round-robin, budgeted downward traces (default 256 per update, world-wide) make trace cost a constant you choose — or skip traces entirely with Owner Location mode, or feed heights from your own terrain data with Manual mode.

• Zero-cost spawn and despawn — instance slots are recycled through a free list, never removed.

• No render-state churn: one batched transform write plus one ranged custom-data write per batch, without recreating the render proxy.

• Nothing to place in the level. A world subsystem creates and owns everything automatically.

• Fully Blueprint-exposed — component, subsystem, stats struct and a function library. A Blueprint-only project can use every feature.

• Built-in profiling: a live stats struct plus the MDS.Enabled 0/1 console variable for an instant A/B against the engine shadows.

• Tunable from Project Settings — quad, master material, batch mode, update rate, trace budget, culling distances and light-refresh interval, without touching code.

• Ready-to-use master material with documented parameters, plus a full rebuild recipe in the docs.

• Playable demo map with a stats HUD, batch spawning and a sun that swings from noon to sunset.

• Full C++ source, Epic coding standard, engine modules only — no third-party libraries.

GOOD TO KNOW

• These are projected blob shadows, not shadow maps: they do not reproduce a silhouette, do not self-shadow and do not receive on walls. Use them for crowds and keep CSM/VSM for hero characters.

• The system follows the scene primary directional light (or an explicit direction override). Point and spot lights do not drive these shadows.

• One draw call per mesh/material pair — mixing shadow quads multiplies batches.

• Requires a shadow-receiving ground surface; shadows land on the ground point beneath each unit.

Documentation: https://github.com/SimulatedFlow/ue-plugin-MaterialDrivenShadows · Support: [email protected]