As in topic, in game I'm creating dynamic roof, but I don't know how change shading from smooth to flat. No matter what I try it's look like on screen.



Is there any in engine way, or only option is calculate them myself? (And since I'm not sure how, maybe somebody can help me with this?)

You could try 2 things:

1) remove mesh vtx normals manually in code, and work with material ambient light, or SetHighlight function

or

2) use "Blend" shader (not "Blend Light"), and just set the material color

I think #2 is simpler

Can't you just properly set the normals for each unique rooftile?

Yes, this is option 3)

MeshBase mesh;
mesh.exclude(VTX_DUP);
mesh.explodeVtxs();
mesh.setNormals();

if having Mesh mesh;
then do first:
mesh.setBase();
MeshBase &base=mesh.parts[i].base;
base.... (as above)
mesh.setRender();
mesh.delBase();

Thanks for help it seems that explodeVtxs() is what I needed.