Simple solution for a complex problem
Option 1:
0 – Make a complete backup of your current Blend file / texture / HDR’s / the works.
1 – Store it on an external medium, so you always can restire this scene when you want to.
>>
2 – Turn OFF all (direct /indirect / HDR-texture based) types of lighting
3 – Turn ON only 1 lightsource at the time.
4 – Render the scene and see what happens.
5 – Goto 3 until the “red-lines-between-the-stair-bricks” issues occurs again.
Option 2:
(Volume) Re-model (as in Computer Aided Design) the entire scene from large basic Blender block (“Mesh Cubes”)
– https://en.wikipedia.org/wiki/3D_modeling
Carve out the spaces / volumes you need by subdividing and loop-cutting your ways out of the big blocks
This approach eliminates all possible ways of creating unwanted seams by default, since you start from one big block.
TIP1: Use the [Recalculate normals functions] to be sure all outside faces are on the outside of the model.
TIP2: Use 2 “(transparant if neccesary) ) Material Colors” in your model:
– 1st “normal” color for the forward facings faces
– 2nd “very odd looking” color for the rearward facings faces.
This can help you to determine where the red-lines truly come from:
– Are they jus reflections from the inside ofyoru model
– Are they causes by outside lightsource
– Option 3,4,n
I wish you happy “Lost-Photon” hunting.
