Tangent Disc Generator (16-bit RGB)

What this does (in one line): Generates a 16-bit RGB image where R/G encode a unit tangent direction field and B encodes a radial falloff (often used as an anisotropy “level”/mask), with robust saving via OpenCV / TIFF / PyPNG.

Why you might care

Physically meaningful channels

R = 0.5·(tx+1), G = 0.5·(ty+1) where (tx, ty) is the normalized tangent around a disc.

B = radial falloff ([0, 1]), controllable via radius_ratio and falloff_gamma.

True 16-bit pipeline for high-precision shading workflows (Unity/Unreal/ DCC tools).

Zero-fuss saving: tries OpenCV (PNG/TIFF) → tifffile (TIFF) → PyPNG (PNG).

Quick start

Clone

git clone https://github.com//tangent-disc-generator.git cd tangent-disc-generator

(Optional but recommended) Create a virtual env

python -m venv .venv && source .venv/bin/activate # Windows: .venv\Scripts\activate

Install dependencies

pip install -U numpy

Any one of the writers below is enough (OpenCV preferred):

pip install -U opencv-python      # preferred

or

pip install -U tifffile

or

pip install -U pypng

Run

python tangent_disc.py

outputs: tangent_disc_16bit.png (or .tif depending on backend)

File name in your repo can be tangent_disc.py (or keep yours). The script writes the image next to the file you run.

Usage

Import and call the function generate_tangent_disc() from tangent_disc.py, or run the script directly:

python tangent_disc.py

Default parameters:

size=2048
radius_ratio=0.48
falloff_gamma=0.6
out_path="tangent_disc_16bit.png"

Generate with custom parameters

generate_tangent_disc(
    size=1024,
    radius_ratio=0.5,
    falloff_gamma=0.8,
    out_path="tangent_disc_16bit.tif"  # extension may be changed by writer
)

Parameters (what they control):

Parameter	Type	Description
size	int	Output is size × size
radius_ratio	float	Disc radius = size × radius_ratio. Outside the disc, B=0
falloff_gamma	float	Gamma applied to radial falloff. Lower → softer falloff; higher → sharper edge
center	tuple | None	(cx, cy) in pixel coordinates; default is image center
out_path	str	Desired base name; actual extension may change depending on backend

Output format & channel semantics

Data type: uint16 (0–65535 per channel).

Encoding

R: 0.5·(tx + 1) mapped to [0, 1] → [0, 65535]
G: 0.5·(ty + 1) mapped to [0, 1] → [0, 65535]
B: max(1 - r/radius, 0) ** falloff_gamma where r is distance to center

Writers (priority): OpenCV (PNG/TIFF) → tifffile (TIFF) → PyPNG (PNG) If your out_path extension is unsupported by the active writer, the code switches to .png or .tif.

Typical use cases

Anisotropic shading: use R/G as tangent directions, B as anisotropy/strength mask.

Flow maps / vector fields: normalized tangent vectors encoded in two channels.

Procedural texturing: stable, high-bit-depth masks and direction guides.