In my render cycle i need one part to not have backface culling, Would it be faster to disable/enable culling, or change the cull mode, then change it back?

Why don''t you just try it.. but both things you do are state changes and they both cost you quite some time.. And what part of engine doesn''t need culling?

There are more worlds than the one that you hold in your hand...

i think itd be faster (but maybe not feasible?) to draw the affected polygons "backwards"...

Well its spacecraft, the models themselves can benifit from culling, but the thrust flames/flares look if they have culling.

are you drawing only one quad/two triangles for the flame then? there must be a better way to do this than just disabling culling.

Whatabout drawing the flame as a sort of textured cone? three or four quads would be all you need if you have a good texture. You could also use billboarding but that tends to not look as good.

at medium detail i would guess that there are 30+polys that make up the thrust, on high there might be as many as 100.

> And what part of engine doesn''t need culling?

Transparent faces