Add support for AxisAlignedBoxSceneQuery for Light

[karriszou]

System Information

• Ogre Version: 13.3.0 (Tsathoggua)
• Operating System / Platform: Ubuntu 20.04
• RenderSystem: OpenGL Rendering Subsystem

Detailled description

I want to query the point light number in a AxisAlignedBox extent, but it not work, because the light.getWorldBoundingBox()(inherited from MovableObject) fuction returns AxisAlignedBox is NULL.

That lead to the query failed:

ogre/OgreMain/include/OgreAxisAlignedBox.h

Line 530 in 05b8dd5

if (this->isNull() || b2.isNull())

It seems that never compute the extents for Light objects:

ogre/OgreMain/src/OgreLight.cpp

Line 275 in f686bd6

// Null, lights are not visible

This question post is in here:
https://forums.ogre3d.org/viewtopic.php?f=2&t=96558&sid=0607b0cdeee4a22ff89d85837926b3ea

Thanks a lot!

[paroj]

It seems that scene query make no sense for directional light, because directional light has no position, but point and spot light has position.
So maybe point and spot light could be regarded as a point when is involved scene query, otherwise they should have a little AxisAlignedBox extent,
so that to participate in the scene query.

that would be the easiest solution.

Another interpretation is the light size - i.e. a directional light is infinitely large, while a point light parametrizes a sphere and a spot-light parametrizes a cone.

That way the query would also include lights that intersect with the Box, but whose origin is otherwise not inside.

Which of these queries are you interested in?

[karriszou]

It seems that scene query make no sense for directional light, because directional light has no position, but point and spot light has position.
So maybe point and spot light could be regarded as a point when is involved scene query, otherwise they should have a little AxisAlignedBox extent,
so that to participate in the scene query.

that would be the easiest solution.

Another interpretation is the light size - i.e. a directional light is infinitely large, while a point light parametrizes a sphere and a spot-light parametrizes a cone.

That way the query would also include lights that intersect with the Box, but whose origin is otherwise not inside.

Which of these queries are you interested in?

Currently the first query(position query) is enough for me, i haven't thought of the second case.

If you have time to implement second query(volume query), perhaps some cool effects can be achieved, such as querying whether the spot light hits an object, and then applying an effect to the object. But it can't be achieved with AxisAlignedBox, since their volume are spheres and cones, so they maybe could have a LightVolume property for volume query purposes, but it's a bit troublesome.

(whisper:I'm an adult, of course I choose both...haha)

Thanks!

[paroj]

this will take more time, as some internal code relies of Lights never being visible. Meanwhile, you could try to use the approach outlined here:
https://forums.ogre3d.org/viewtopic.php?t=60664

[karriszou]

this will take more time, as some internal code relies of Lights never being visible. Meanwhile, you could try to use the approach outlined here: https://forums.ogre3d.org/viewtopic.php?t=60664

Yes, the approach of the post is feasible, in addition i can make a small modification in the source code for the purpose, since only the position query is required.

Thanks for your help!

[paroj]

the thing to consider is, when you give lights a bbox, they are included in the scene bbox too. This is then used to e.g. compute the required shadow-map size.
If one was to give the directional light the correct bbox (infinite), it would break shadows. Thats why I am hesitant.

However, the bounding sphere of the scene already includes lights (as points), so it is probably safe to do the same with bboxes.