Inaccurate shadows when the shadow is cast onto a non-CastShadow object

[Abcreator]

This bug affects both Future and ShadowMap lighting technologies.

I was recently optimising my games by disabling CastShadow on the floor parts of my game however I noticed that the shadows became inaccurate upon doing so:

Floor (Red) has CastShadow enabled:

Floor (Red) has CastShadow disabled:

Expected behaviour:

I expect the shadows when CastShadow is disabled on the part it’s being cast onto to be the same as when CastShadow is enabled.

Actual behaviour:

Shadows get extremely thin (to a point in where they aren’t visible), where the parts (casting the shadow) are near the part that has CastShadow disabled.

I would like to see this fixed soon as I am unable to to disable CastShadow on any of my floor tiles until this is fixed. (which hinders performance)

[OuterspaceNemo (Nemooo)]

Hello! Can you please attach a repro place and list active Beta features and any potentially related Plugins? Haven’t been able to reproduce the issue. Thanks!

[Abcreator]

I have no beta features enabled / plugins that could be affecting this. As seen in the following place, the pole has the buggy shadows as the baseplate has CastShadows disabled… Repro.rbxl (28.8 KB)

[vrtblox]

this is by design, so you shouldn’t disable cast shadows for things that should receive shadows

[jufdnhf]

Shouldn’t CastShadow when disabled just not cast a shadow, but be able to have shadows casted onto it? Whichever way, the shadows shouldn’t be buggy, either normal shadows or no shadows?

[vrtblox]

this is the limitation of the method used. its a tradeoff so we could have better shadows/performance

[Abcreator]

This limitation of the engine makes the CastShadow property only useful on instances that you know will never get a shadow cast onto it (player characters also cast shadows, so that makes any place a player can get to not viable for non-CastShadow instances). It also holds back any developers who want to make a part that has no shadows since there is no way to do so (without having inaccurate shadows).

Maybe some setting could be made that enables a fix to this, with the performance decrease + worse shadows (that you mentioned would happen).

[Abcreator]

And as stated in the OP casting shadows on that part, causes inaccurate shadows.