Control Map Format

Godot doesn’t fully support integer Image formats. So, we store the data as a 32-bit float Image and Texture. However, we read or write pixels as a 32-bit unsigned integer. We do not convert int/float values so there is no precision loss. The values are meaningless interpreted as floats. We read or write 32-bit uints directly from/into the memory block, both in C++ and the shader.

We process the uint as a bit field with the following definition, starting with the left most bits:

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

• Encode/decode work in C++ or GLSL and may need a u at the end of literals when working with an unsigned integer. e.g. x >> 14u & 0xFFu.

• 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+

  • 2 bits - 4 layers (including Hole above, eg water, non-destructive, hole, normal mesh)

  • 1 bit - future use (maybe added to particles)

  • 2 bits - Texture blend weight array index+

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

The 3 bit indices above are used to select a value from an 8-index array of values between 0-1, such as { 0.0f, .125f, .25f, .334f, .5f, .667f, .8f, 1.0f }; This allows us to store full range 0-1 values that would normally require 8 bits (256 values) in only 3 bits (8 values), since the fine gradations are not important. This idea came from the Witcher 3 presentation.

C++ users can use the conversion and testing functions found in util.h