Convert control map from 8/8/8 to 5/5/3/1

[TokisanGames]

See discussion here: #64

Currently control paints and reads RGB8 in 8/8/8 bit floats as base/overlay/blend.

New format is 32-bit unsigned integer (stored as RF since Godot doesn't support int formats in all cases). Here is the definition starting with the left most bits.

Description	Range	# Bits	Bit #s	Encode (C++)	Decode (GLSL)
Base texture id	0-31	5	32-28	(x & 0x1F) <<27	x >>27u & 0x1Fu
Overlay texture id	0-31	5	27-23	(x & 0x1F) <<22	x >>22u & 0x1Fu
Texture blend	0-255	8	22-15	(x & 0xFF) <<14	x >>14u & 0xFFu
... reserved ...
Hole: 0 draw terrain, 1 discarded	0-1	1	3	(x & 0x1) <<2	x >>2u & 0x1u
Navigation: 0 no, 1 yes	0-1	1	2	(x & 0x1) <<1	x >>1u & 0x1u
Autoshader: 0 auto, 1 manual	0-1	1	1	x & 0x1	x & 0x1u

• Possible future plans for reserved bits:

  • 5 bits - 32 paintable particles
  • 3 bits - paintable uv scale array index+
  • 3 bits - paintable slope array index+
  • 3 bits - paintable rotation array index+
  • 1 bit - paintable navigation mesh
  • 2 bits - 4 layers (including Hole above, eg water, non-destructive, hole, normal mesh)
  • 1 bit - future use (maybe added to particles)
  • | Texture blend weight array index+ | 0-7 | 3 | 22-20 | (x & 0x7) <<19 | x >>19u & 0x7u

• Array for all + marked 3-bit indices above: { 0.0f, .125f, .25f, .334f, .5f, .667f, .8f, 1.0f };

Also see #64, #4, #60

[Saul2022]

Out of curiosity , wouldn't this give a performance improvement by pushing more the 32 texture limit?

[TokisanGames]

We already hard limit the texture count to 32. The new control map format keeps that limit. All it does is compress 32 texture index stored in 8 bits to 5 bits. No performance difference.