replace CEGs &/ write lua replacement for defaultexplosiongenerator

[Bluestone]

should probably wait until #722 is fixed before doing things connected to lups

[beherith]

Please avoid using lua where perfectly usable engine functionality exists. I might be ignorant, but i see no need for lua in this case.

[Bluestone]

I thought this was your idea?!

But - I think that this is only way to replace the engines crazily expensive smoke effect with cheaper ones. I don't think usedefaultexplosions does much else besides smoke, but nix probably knows better than I. I didn't look at it yet.

All a lua replace would do is run in XXXdefs_post and recreate params previously created by usedefaultexplosions, so there is no perf cost associated (apart from the exposions themselves, which would be strictly cheaper).

[beherith]

Sorry, i misunderstood your intent.

Usedefaultexplosions will not actually generate CEG's, the engine does this through 'magic' constants. I can link to the relevant source files, as I have read them once...

[Bluestone]

That wouild be handy. I think defaultexplosion is a combination of magic constants and the unitdef involved in the explosion.

[Bluestone]

This can only be done (properly) after #891 is fixed.

[Bluestone]

Also need ​https://springrts.com/mantis/view.php?id=4921