osg::NodeVisitor is designed to recursively call virtual apply signatures until we find an implemented signature. Encountered nodes that we do not explicitely handle will trigger additional virtual function calls. With this PR we avoid these additional virtual function calls in the particularly costly ComputeLightSpaceBounds by adding some explicit signatures.
Currently, we always traverse the scene graph an additional time with a ComputeLightSpaceBounds visitor during shadow casting. ComputeLightSpaceBounds is only useful when the shadow casting mask allows us to shrink the bounds of the rendered scene, so we guard its traversal with a check against getCastsShadowTraversalMask. In practice, this guard never works because we build the traversal mask inclusively.
With this PR we limit the getCastsShadowTraversalMask check to relevant masks. This new check allows us to skip a superfluous ComputeLightSpaceBounds traversal with most settings.
Currently, we create a new ComputeLightSpaceBounds visitor per frame. Within this visitor, we require excessive memory allocations, mainly a new osg::RefMatrix per encountered Transform node.
With this PR we reuse a single ComputeLightSpaceBounds visitor across frames and enable the createOrReuseMatrix functionality to avoid allocating new matrices every frame. osgUtil::CullVisitor internally uses the same approach.
The docs seem to imply this is automatic when the array contains a
class-type, which osg::ref_ptr is, but I got a crash log that doesn't
make sense if that's true.
As we don't reconfigure all shaders without shadows when we disable them
indoors (as it'd probably add a hitch to transitioning in and out) we
need to set up dummy state so the shaders don't do anything illegal.
This hadn't had symptoms for most objects as when indoors, nearly
everything would be drawn first in one of the water RTTs, which had
dummy state to disable shadows already. This wasn't true of the water
plane itself, though, yet somehow it took until just now for anyone to
report that.
This resolves vtastek's issue where the water would be invisible indoors
Previously we always discarded shadow map fragments if the alpha channel of the output would have been low, but there were some (modded) assets that have non-one alpha but have testing or blending disabled so end up opaque anyway. This lets the shadows of those objects match.
