I do have some light effect on some objects like this tree.
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If I can have shadows on the sides of the trunk that are not lighted, it should be possible to have no light on the side of a wall that is not lighted as well
Light sources unfortunately have no effect/shadows in game on scenery objects (only terrain). And shadows are only casted by natural light (sun/moon).
The same was with Planco. Apparantly it is hard to code this out. I don't expect it to be fixed, but it is a valid suggestion nonetheless.
Self-shadowing and casting shadows on other objects is oftentimes handled differently by render engines for optimization reasons.
With self-shadowing, there is only one objects to be calculated. I also somehow doubt, that multiple light sources will add up to multiple and differently lit shadow areas on the tree (I haven’t tried it though.)
With real (ray-traced) shadows, multiple objects would cast and recieve shadows from multiple lights. This can get taxing to the GPU quite fast. The issue is amplified by the fact that PZ is a creative game where the player can spam lights to his heart’s content and the developer has no control over the calculation load other than reducing it as much as needed by limiting the calculated shadows quality beforehand.
It's not a question of programming, it has more to do with performance. If every object would cast shadows from every lightsource it would very quickly drown the fps to a standstill. Shadow calculations are among the most heavy burdens on performance, they take a lot of drawcalls and calculations in realtime.