[macmv]

What

Turns terrain-inspector (the old spline editor) into a 3D view of the real terrain generator, so splines and generator parts can be changed live.

rgen crates (behind the new inspector feature, off for the game and jni)

• Splines at runtime: rgen_biome::Splines and set_splines() swap the height splines that WorldBiomes::sample_height reads. Without the feature it reads the statics as before.
• Unknown props: with rgen-world/inspector, encode falls back to a block's default state instead of logging an error and using meta 0, since the inspector has no block registry.
• rgen_world::Region: generates and decorates a rectangle of chunks on the calling thread. It doesn't use CachedWorld.
• rgen_biome::toggles: parts of the generator that can be turned off, in the order the generator applies them: 3D density noise, caves (noodle, cheese, and their parts), biome variety, surface layers, biome patches, ores, decorations, and each decoration by name. A turned-off decoration still takes its random numbers, so the others stay in place. Without the feature, the checks compile away.

terrain-inspector

• Always generates the blocks with the real generator, colored by block kind. The heightmap path is gone.
• A "Terrain generator" section lists the toggles as an expandable tree.
• "Color by" can color every block by a spline/noise value (final height, continentalness, erosion, and so on) or by biome.
• Spline edits recolor right away. The terrain regenerates when the mouse is let go, as does a toggle change.
• The atlas is sized by view distance, scrolling zooms towards the mouse, and chunks that are all one block take no atlas slot.

Testing

• cargo test -p terrain-inspector
• cargo test -p rgen-biome --features inspector (a region through Region, and the toggles changing the output)
• Ran the app and checked that the shader compiles and tiles generate. I haven't gone through the toggle panel or the layer colors by hand.