Re: [Plib-devel] Texture and blend modes

[Steve B. <sjb...@ai...>]

"Curtis L. Olson" wrote:

> Let's see if I understand ...
> 
> I am (by definition) not tweaking any states that ssg normally would
> manage.

Indeed.

>  But, since these states are grouped, and doing a
> glPushAttribute() saves a whole slew of states, I may unwittingly
> alter a state that ssg *does* manage as a side effect of my
> glPopAttribute()

Yes - by accidentally restoring it to the state BEFORE the most
recent state->apply.
 
> I'll give it a try in my sky code ...
> 
> Here's what I get now:
> 
> no matching function for call to `ssgEntity::hasState ()'
> no matching function for call to `ssgEntity::getState ()'

Doh!  These are only members of ssgLeaf - general purpose entities
don't have states unless they happen to be leaf nodes.
 
> A check of ssg.h indicates that these are indeed not members of
> ssgEntity.

Yep.
 
> But, the compiler lets me get away with this ... sound reasonable?
> 
>     ssgLeaf *f = (ssgLeaf *)e;
>     if ( f -> hasState () ) f->getState()->apply() ;

Yep - so long as you only attach this callback to a leaf node.

If you were playing it super-safe you could do an 'isAKindOf' test to
check before you did the cast.
 
> I'll play around with this some more.  I'm still having a touch of bad
> luck with GL_DEPTH_TEST, but I'm forcing this in other places in my
> code too.  Could be that I'm entering the code with it off and since
> the sky code is actually preserving the state rather than turning it
> [back] on when it is done, I could be exiting they sky rendering
> section with the state set different now.

Urrrggggg ... brainnn ... can't ... quite .... reach ...

Hold on - it's coming <rumble> - yes - comprehension is dawning <creak>
<rattle> <rattle> *POP* 

      Yes.

By doing this "right" you could actually be cancelling out one
half of an elegant matched pair of antique Colonial bugs...which
erm...greatly reduces their value.

Hmmm - so this might mean that my explanation is not the right one (although
it's still "TRUE" and must still be attended to).

-- 
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