Rendering Architecture

Rendering Architecture & Cetacean Physics

Unlike sprite-based animation systems, git-tulkun uses pure mathematical procedurals. Every frame is synthesized on the fly in Rust.

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1. Spine Spline and Signed Distance Fields (SDFs)

The torso is represented as a flexible central spline containing up to 186 nodes. Appendages (opercular flippers, primary scythe wings, kuru neural whips, pelvic paddles, and caudal flukes) are anchored to the spine and evaluated using signed distance chains.

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2. Cylindrical Normal Lighting

For each pixel $(x, y)$ inside the body or appendages, a 3D cylindrical surface normal vector is calculated:

$$\vec{n} = \left(n_x, n_y, \sqrt{\max\left(0, 1 - n_x^2 - n_y^2\right)}\right)$$

This normal is dotted with an ocean key light vector:

$$\vec{L} = [-0.30, -0.62, 0.72]$$

The resulting intensity is dithered using a $4\times4$ Bayer matrix to achieve authentic 90s-era retro pixel shading.

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3. Cetacean S-Wave Swimming Loop

The swimming animation loops over 48 frames at 15 FPS (3.2 seconds):

$$\Delta y(u, t) = A_{\text{head}} \cdot \sin(\omega t) \cdot (1 - u)^{1.3} + A_{\text{tail}} \cdot \sin(2.35\pi u - \omega t) \cdot u^{0.92}$$

• $u \in [0, 1]$ represents normalized distance along the spine from rostrum to fluke.
• The head maintains steady posture with subtle vertical heave, while a traveling wave accelerates down the tail stock to drive the propulsion flukes.
• Pectoral flippers scull with natural hydrodynamic phase lag.