Disc2Variation.cs

using System;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Model;
 
namespace Waher.Script.Fractals.IFS.Variations.Flame
{
    public class Disc2Variation : FlameVariationMultipleParameters
    {
        private readonly double rotation;
        private readonly double twist;
 
        public Disc2Variation(ScriptNode rotation, ScriptNode twist, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { rotation, twist }, new ArgumentType[] { ArgumentType.Scalar, ArgumentType.Scalar },
                  Start, Length, Expression)
        {
            this.rotation = 0;
            this.twist = 0;
        }
 
        private Disc2Variation(double Rotation, double Twist, ScriptNode rotation, ScriptNode twist, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { rotation, twist }, new ArgumentType[] { ArgumentType.Scalar, ArgumentType.Scalar },
                  Start, Length, Expression)
        {
            this.rotation = Rotation;
            this.twist = Twist;
        }
 
        public override string[] DefaultArgumentNames
        {
            get
            {
                return new string[] { "rotation", "twist" };
            }
        }
 
        public override IElement Evaluate(IElement[] Arguments, Variables Variables)
        {
            double Rotation = Expression.ToDouble(Arguments[0].AssociatedObjectValue);
            double Twist = Expression.ToDouble(Arguments[1].AssociatedObjectValue);
 
            return new Disc2Variation(Rotation, Twist, this.Arguments[0], this.Arguments[1],
                this.Start, this.Length, this.Expression);
        }
 
        public override void Operate(ref double x, ref double y)
        {
            double d2rtp = this.rotation * Math.PI;
            double s0 = Math.Sin(this.twist);
            double c0 = Math.Cos(this.twist);
 
            if (this.twist > pi2)
            {
                double k = 1 + this.twist - pi2;
                s0 *= k;
                c0 *= k;
            }
 
            if (this.twist < -pi2)
            {
                double k = 1 + this.twist + pi2;
                s0 *= k;
                c0 *= k;
 
            }
 
            double t = d2rtp * (x + y);
            double sinr = Math.Sin(t);
            double cosr = Math.Cos(t);
            double r = Math.Atan2(x, y) / Math.PI;
            x = (sinr + c0) * r;
            y = (cosr + s0) * r;
        }
 
        private const double pi2 = 2 * Math.PI;
 
        public override string FunctionName => nameof(Disc2Variation);
    }
}