Increase the default texel size for lightmap baking

[Calinou]

This has several benefits:

• Baking is now significantly faster out of the box (often twice as fast).
• Lightmap texture file sizes are often divided by 2 or 3.
• Baking requires less memory and is less likely to crash on large scenes.

Visual quality may be degraded, but it's usually not very noticeable in the default configuration where only indirect lighting is baked.

Testing project: https://0x0.st/o8oM.zip _{(link expires in October 2022)}

Preview

Due to bicubic sampling not being reimplemented in master yet, the difference between the two texel sizes is more noticeable than it would be with bicubic sampling enabled. Once bicubic sampling is reimplemented, the quality loss will be less visible.

Indirect lighting baked only

Textured

This represents a typical usage scenario with a textured scene.

Before	After

Untextured

This represents a worst-case scenario for lightmaps where the texel size difference is the most noticeable.

Before	After

Fully baked lighting

Textured

This represents a typical usage scenario with a textured scene.

Before	After

Untextured

This represents a worst-case scenario for lightmaps where the texel size difference is the most noticeable.

Before	After

[akien-mga]

We discussed with @JFonS that it's OK to increase this default, but we should probably have a warning system that can assess how much memory a bake would take and whether the texel sizes of the imported models are sensible for the size of the scene - since eventually what texel size makes the most sense is heavily dependent on the scene size.

[akien-mga]

Thanks!