OldThink/Content.Shared/_White/Spline/Spline.cs

using System.Runtime.CompilerServices;

namespace Content.Shared._White.Spline;

public abstract class Spline<T> : ISpline<T>
{
    public abstract T SamplePosition(ReadOnlySpan<T> controlPoints, float u);

    public abstract T SampleVelocity(ReadOnlySpan<T> controlPoints, float u);

    public abstract (T Position, T Velocity) SamplePositionVelocity(ReadOnlySpan<T> controlPoints, float u);

    public virtual IEnumerable<float> IteratePointParamsByLength(T[] controlPoints, float lengthStepSize)
    {
        //ну а хули нам наивным салюшонам
        for (var u = 0; u < controlPoints.Length - 1; u++)
        {
            var segmentLength = ApproximateArcLength(controlPoints, u);
            var tStepSize = lengthStepSize / segmentLength;
            for (var t = 0f; t < 1; t += tStepSize)
            {
                yield return u + t;
            }
        }
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public virtual float GetControlGroupAmount(int controlPointAmount)
    {
        return controlPointAmount - 1f;
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    protected virtual float ApproximateArcLength(ReadOnlySpan<T> controlPoints, float u)
    {
        return Magnitude(Subtract(controlPoints[(int) u], controlPoints[(int) u + 1]));
    }

    protected abstract T Add(T op1, T op2);

    protected abstract T Subtract(T op1, T op2);

    protected abstract float Magnitude(T op1);
}