SolarSystem scenario PSSM shadows artifacts

[Lax]

Hi all,

I'm working on a solar system component in Ogre-Next. Planets and moons orbit a sun at huge distances (orbital radii in the hundreds of thousands of units, farClip ₁,000,000 in space).

When the player lands on a planet or moon, I freeze it. I snap farClip down to ₅₀₀₀ and enable PSSM shadows with lambda=0.95 for tight cascade coverage on the surface.

The problem: the scene's overall AABB is enormous (the whole solar system), and the shadow camera frustum seems to be influenced by that even though the player is only ever within a ₅₀₀₀ unit radius of the frozen body's surface.

Questions:

1. Is there a way to explicitly constrain the PSSM shadow camera's focus region to a specific world-space AABB (e.g. centred on the frozen planet, radius ₅₀₀₀) so it ignores the rest of the solar system geometry entirely?
2. Should I be using a dedicated shadow-only compositor workspace for the surface, or is tuning the ShadowTextureDefinition (pssmLambda, split points, etc.) the right approach?
3. Is there anything in the CompositorShadowNodeDef or SceneManager I should set to exclude out-of-range objects from shadow caster culling when farClip is small but the scene AABB is huge?

Thanks a lot!

Best Regards
Lax

[dark_sylinc]

The best flexibility would be to derive from PSSMShadowCameraSetup and inject it (though CompositorShadowNode::CompositorShadowNode doesn't have a way to inject them... mmm)

Is there anything in the CompositorShadowNodeDef or SceneManager I should set to exclude out-of-range objects from shadow caster culling when farClip is small but the scene AABB is huge?

Yes. CompositorShadowNodeDef::mMinRq and CompositorShadowNodeDef::mMaxRq control that.
Put all "space" non-shadow casting objects outside of that render queue range. Visibility masks should also work (see SceneManager::_calculateCurrentCastersBox). IIRC objects with setCastShadows(false) should already be getting ignored though. If you're already doing that an your caster box is still huge, you may want to debug internally to see why it gets so big (you probably forgot to call setCastShadows on an object on the other side of the galaxy).

However I wouldn't rule out the possibility some of that math somewhere is using the whole scene's AABB, causing floating point issues.

For example in FocusedShadowCameraSetup::getShadowCamera it calls:

Code: Select all

cam->getCustomWorldSpaceCorners( corners, farDistance );

Which I believe is on the normal camera. Thus whether that number goes crazy will depend on your far distance parameters on the regular camera.

[Lax]

Hi,

ok thanks! Then i know what to adapt.

Best Regards
Lax