Blocky shadows when baking lighting

[AcidArrow]

It’s either UV errors or Invalid texel artifacts:

These are the relevant parts from the troubleshooting guide:

Lightmapping Troubleshooting Guide

Chapter 9: Lightmap UV artifacts [8467001--1124813--LightmapUVs-Overlaps-Combined.jpg] Figure 18. Lightmapped objects exhibiting severe artifacts due to missing lightmap UVs (left). Same objects with correctly authored lightmap UVs (right). 9.1 Why does this happen? Unlike regular texture UVs, lightmap UVs have different requirements: It cannot contain any overlaps. It must have enough padding between UV shells. It should have minimal area and angle distortion. It should be uniformly scal…

Lightmapping Troubleshooting Guide

Chapter 15: Invalid texel artifacts [8467202--1124918--InvalidTexels-ETR-DoubleSidedGIOff-Combined.jpg] Figure 35. Scene containing a one-sided curtain mesh which causes invalid texel artifacts to appear after baking (left). Texel Validity scene view mode highlights invalid texels in red (right). Notice how saturated invalid texels are around the curtain area. 15.1 Why does this happen? Sometimes, invalid texels can be the cause of blocky artifacts in a lightmap. Unity can mark Lightmap t…