[3.x] Allow non-power-of-two directional shadow size in 3D

[Calinou]

3.x version of #54041.

This allows for more finegrained performance/quality tuning, especially at higher sizes. Any number can be used. For directional light shadows, 3072 and 6144 are sensible shadow sizes that can be used if the default 4096 is too slow or too low-resolution for a large scene.

This change only applies to GLES3, as NPOT texture support is not present on all devices that support GLES2. When using GLES2, shadow sizes are still rounded up to the nearest power of 2. It might be possible to support it regardless, but I'd rather not risk it, especially on mobile platforms.
Edit: Temporarily allowed in GLES2 to check if it works on mobile/web platforms.

This also updates the point light shadow atlas size property hint to reflect that it can be changed without restarting the engine.

Preview

Point light

point-shadow-size-npot-3.x.mp4

DirectionalLight

4096 (default)

6144 (new possible value)

8192

[clayjohn]

Does this work well when using many lights in the shadow atlas? AFAIK the reason it was limited to power of 2 was because the shadow atlas is recursively subdivided to provide space for all the shadow maps. I am concerned that odd numbers may lead to odd rendering artifacts when many lights are used.

[Calinou]

Does this work well when using many lights in the shadow atlas? AFAIK the reason it was limited to power of 2 was because the shadow atlas is recursively subdivided to provide space for all the shadow maps. I am concerned that odd numbers may lead to odd rendering artifacts when many lights are used.

I've tested it again with a larger scene and can confirm that point light shadows break with NPOT sizes 🙁

I reverted the change for the point light shadow atlas size, but I kept it for the directional shadow size.

The behavior in master is strange: NPOT sizes for the point light atlas look fine with no visible rendering glitches regardless of the size chosen. However, I occasionally get error spam:

ERROR: Condition "!li->shadow_atlases.has(p_shadow_atlas)" is true. Returning: 0 at: light_instance_get_shadow_texel_size (servers/rendering/renderer_rd/renderer_scene_render_rd.h:1009)

Testing projects:

• test_shadow_npot_3.x.zip
• test_shadow_npot_master.zip

[Calinou]

I've amended this PR to allow setting the directional shadow size to NPOT values in GLES2 as well. Based on my understanding, NPOT textures in GLES2 work as long as they aren't set to repeat and have no mipmaps. So far, it works on my desktop PC, but it needs to be tested on Android and HTML5 at least.

2048

3072 (new possible value)

4096