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Source Angle

Where: select a Directional Light, then find Source Angle in its Details panel under Light.

Source Angle is the apparent diameter of the light source in degrees. It describes how large the sun looks from a surface, not which direction it shines. Rotate the Directional Light to change the direction; adjust Source Angle to change its apparent size. See Epic's Directional Light property reference.

What changing it looks like​

A smaller source produces sharper shadows on paths that account for light size. A larger source spreads the shadow transition over a wider area. The transition generally grows with the distance between the caster and receiver, so contact can remain defined while a distant shadow softens.

For example, compare the shadow at the base of a pillar with the shadow of its top. Increasing Source Angle should be judged across both, not only at the contact point.

How it fits Spectral​

Spectral passes the Directional Light's Source Angle into its bake light parameters. Set it before baking when you want the saved lighting to match the intended source size.

For live soft shadows, check the active shadow method and PCSS controls. Source Angle describes the light; PCSS quality and filtering determine how a supported runtime path represents that softness. This property is not a guarantee that every shadow method will use the same result.

What it does not change​

  • It does not increase the light's intensity.
  • It does not increase lightmap resolution or shadow-map resolution.
  • It does not add fog or automatically create visible sun shafts.
  • It is not Source Soft Angle, which is a separate Unreal property.

Point and Spot Lights describe their source size with controls such as Source Radius and Source Length. Rect Lights use their width and height. Do not look for the Directional Light's degree-based control on every light type.

Softness is not a repair for low resolutionTip

If a shadow is stair-stepped or missing thin details, check the shadow data's resolution first. A wider soft edge can hide some artifacts, but does not restore missing detail.

When to rebake​

Rebake to update saved lighting after changing Source Angle. Supported runtime shadow paths may react immediately, but that does not mean existing lightmaps and probes have been rebuilt.