On Thursday 25 January 2007 14:44, AJ MacLeod wrote:
> On Thursday 25 January 2007 10:21, Yurik V. Nikiforoff wrote:
> > There are objects with transparent textures - part of visual model or 3d
> > instruments. If two or more such objects overlaps, there is wrong
> > appearance.
> > I found, that appearance of transparent objects depend from sequense this
> > objects in ac file. But there is no methods for control of object
> > sequence in 3d editors (like ac3d).
>
> Actually, there are, (in AC3D, and ISTR in blender too) though they might
> not be very obvious in AC3D at least... I know someone else had to point
> them out to me. In AC3D, from the tools menu select heirarchy view. You
> are shown a view of the complete tree of objects and groups; if you right
> click on any object or group you can select "move to head" or "move to
> tail" and change the object ordering that way.
>
> There was also a simple ordering animation which could be done in the FG
> XML file using a "none" animation type, but simply listing the objects in
> <object-name> tags in the desired order. I'm not sure whether that still
> works with OSG or not (I've never used it myself anyway AFAIK). It's
> mentioned in the model-howto.html
>
> If you would like yet another way, Melchior has a python script called
> ac3d-scan which I think would also do what you want
> http://members.aon.at/mfranz/ac3d-scan
That does not help here since osg has its own way to determine which
osg::Drawbles are drawn at which time. So depending on your view the soring
happens within osg.
I am aware of that sorting problem, and thinking about that ...
Anyway, osg has many stages it renders, and transparent stuff is sorted back
to front anyway, but that sorting takes needless time if solid geometry is
put into the transparent renderbin. To decide this the ac3d loader for
example looks if we have either a alpha value not equal to 1 in the current
material or if there is *any* pixel in the texture that has an alpha value
not equal to 1.
That way the c172 fuselage is something that is potentially transparent to osg
and sorted back to front.
Or in other words: we should not attach semitransparent textures to solid
objects to avoid overhead in this area ...
Greetings
mathias
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