Initial commit

arm9/source/animation/CubicBezierCurve.h

@@ -0,0 +1,48 @@
+#pragma once
+#include "Curve.h"
+
+class CubicBezierCurve : public Curve
+{
+    using fx = fix16<13>;
+
+    const fx _cx;
+    const fx _bx;
+    const fx _ax;
+
+    const fx _cy;
+    const fx _by;
+    const fx _ay;
+
+    [[gnu::noinline]]
+    static constexpr fix32<26> SampleCurve(fx ax, fx bx, fx cx, fx t)
+    {
+        return ((ax * t + bx) * t + cx).LongMul(t);
+    }
+
+public:
+    constexpr CubicBezierCurve(fx p1x, fx p1y, fx p2x, fx p2y)
+        : _cx(3 * p1x)
+        , _bx(3 * (p2x - p1x) - _cx)
+        , _ax(1 - _cx - _bx)
+        , _cy(3 * p1y)
+        , _by(3 * (p2y - p1y) - _cy)
+        , _ay(1 - _cy - _by) { }
+
+    [[gnu::noinline]]
+    fix32<26> Compute(fix32<26> t) const override
+    {
+        fx start = 0.0;
+        fx end = 1.0;
+        while (true)
+        {
+            const fx midpoint = (start + end) >> 1;
+            const fix32<26> estimate = SampleCurve(_ax, _bx, _cx, midpoint);
+            if ((t - estimate).Abs() < 0.001)
+                return SampleCurve(_ay, _by, _cy, midpoint);
+            if (estimate < t)
+                start = midpoint;
+            else
+                end = midpoint;
+        }
+    }
+};