March 15, 2026
Curve Wars: Just Lerp It
Slicing Bezier Surfaces
Dev says “just lerp it” to slice curvy surfaces — and the comments split in half
TLDR: A dev showcased slicing smooth computer‑drawn surfaces by repeatedly blending points—a known method for Bezier curves. The crowd split: one side questioned how a simple blend works on a non‑linear curve, while math folks explained it’s standard subdivision using Bernstein polynomials, making the trick both practical and legit.
A JavaScript dev dropped code showing how to slice a wiggly computer‑made surface into neat pieces using a super simple trick: lerp, short for linear interpolation, basically averaging points between A and B. Sounds chill—until the comments erupted. One reader, vintagedave, was baffled: Bezier curves (those smooth lines used in logos and 3D tools) are non‑linear, so how can a straight‑line blend be legit? Cue the math squad.
Enter sfpotter, who calmly declared this is classic subdivision—the same math behind Pixar‑style curves—explaining it’s about Bernstein polynomials and the “blossom” idea. Translation: the fancy curve can be rebuilt by repeatedly blending its control points, a known trick called de Casteljau’s algorithm. Drama level: medium spicy. The vibe split into two camps: “Just lerp it, bro” vs “Show your proofs.”
Meanwhile, the dev’s demo slices a surface by cutting its underlying curves into halves at different t values (a 0–1 slider), then recombining the halves. Fans cheered the “it just works” pragmatism for quick modeling, while purists begged for clearer math breadcrumbs and variable names. Memes flew—“Bezier Bisection Brigade” and “Blossom or bust”—as the thread turned into a crash course in curve math disguised as a code snippet. If you’ve ever wondered how design tools carve up curves, the comments basically said: yes, you can slice it cleanly—and yes, there’s real math magic behind it.
Key Points
- •A JavaScript function splits a cubic Bezier curve at parameter t using linear interpolation to produce two exact curve segments.
- •The function returns two sets of control points that reconstruct the original curve when combined.
- •The approach is extended to slice Bezier surfaces by iteratively subdividing and assembling control grids.
- •Surface segmentation uses parameters: wide (horizontal slices) and fall (vertical segmentation).
- •Each iteration creates a new surface patch object with updated width and control points from the subdivided halves.