The blintz base starts from a square sheet. Its crease pattern is the diamond formed by connecting the midpoints of the four edges — this is not arbitrary: the crease for folding any corner onto the center is exactly the perpendicular bisector of the segment joining that corner to the center, and for a square that bisector always passes through the two adjacent edge midpoints. Each corner then folds along its crease as a rigid hinge rotation.
hinge = midpoint(edgeMid_a, edgeMid_b)
axis = normalize(edgeMid_b − edgeMid_a)
v(θ) = (corner − hinge)·cosθ + (axis × (corner − hinge))·sinθ
point(θ) = hinge + v(θ), θ: 0 → π
Because hinge is the true perpendicular foot from the corner to the center, this rotation is exact: at θ = π the corner point lands precisely on the center, at θ = π/2 the flap stands vertical mid-fold, and every intermediate θ is a physically valid partial fold — not an interpolated shape swap.
- Fold progress — drives all four corners in sequence (0–25% folds the first corner, 25–50% the second, and so on), the same order a real folder works around the sheet.
- Play / Reset — animates the sequence automatically, or snaps back to the flat, unfolded square.
- Fold speed — how fast progress advances per second while playing.
- Layers at center — the base diamond plus every corner that has fully landed on it; a finished blintz base stacks five layers of paper at its center point, which is exactly why it resists further precise folding and most origami sequences use it only as a starting base.
Real-world relevance: the blintz base is the seed of many classic bases (bird base, frog base, waterbomb variants) — get this single fold's geometry wrong and every model built on top of it is off.