The rectangle lights ignore the specular value of lit materials and will apply a specular highlight to them regardless of the value. you can compare the result against a standard point light and you will not see a specular highlight for those.

Steps to Reproduce

Create an Empty Scene

Create a new material and connect a constant 0 value to Base Color, Metallic,Specular, Roughness,Anisotropy,Emissive Color.

Add sphere mesh to scene and apply material.

Add a rectangle light.

Observe specular reflection on sphere surface.

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ComponentUE - Graphics Features
Affects Versions4.26.1
Target Fix5.1
CreatedSep 30, 2021
ResolvedNov 3, 2021
UpdatedNov 5, 2021
View Jira Issue