# two sided polygons

for various stuff that are typically drawn with 2sided polygons ie (cullface == off) eg windows, special fx etc

has anyone experimented using 2 polygons back to back (maybe a small dist between) vs a single polygon with cullface == off

pluses with 2 polygons include
A/ more realistic as physical objects have thickness
B/ less state changes
C/ certain apps dont recognize 2sided polygons

i cant see any minuses (except double the geometry) but would like to here if anyones run into issues doing this?

cheers zed
theyll split your pretty cranium and fill it full of air

A/ more realistic as physical objects have thickness

But if you looked at one of these objects from the side, you’d see the gap between the two polygons. Putting them close enough together where there is no gap kills any sense of thickness. So I don’t see this point. Points B & C make sense though.

-SirKnight

zed wrote:
has anyone experimented using 2 polygons back to back (maybe a small dist between) vs a single polygon with cullface == off
We use 2 sets of polys for some translucent surfaces to have different tesselation depending on viewpoint. Works fine. Only one set of vertices are used though, so there is no thickness involved.

But if you looked at one of these objects from the side, you’d see the gap between the two polygons. Putting them close enough together where there is no gap kills any sense of thickness. So I don’t see this point. Points B & C make sense though
true, i changed a building model’s windows to having 2 polygons and it looked better (than 1 polygon with cullface turned off) the gaps are hidden as the glass panes go into the struts

but ive thought of the case ingame where i most often use cullface off polys, and thats where when a model gets destroyed + breaks up into pieces, ie so u can see the hidden insides of objects. thus polygon cull has to be turned off. i see no other way (unless u use some complicated method to sohow create a mesh with thickness from each broken piece, this would be nice for shadowing if i do it like this though)
so i think ill stick with what im doing (the standard copout method)
cheers

true, i changed a building model’s windows to having 2 polygons and it looked better (than 1 polygon with cullface turned off) the gaps are hidden as the glass panes go into the struts

Well as long as you can hide that gap, I’m all for it.