Kav/Effects/DirectionalLightCollection.cs

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;

namespace Kav
{
    public class DirectionalLightCollection
    {
        private readonly Vector3[] directions = new Vector3[4];
        private readonly Vector3[] colors = new Vector3[4];
        private readonly float[] intensities = new float[4];

        readonly EffectParameter lightDirectionsParam;
        readonly EffectParameter lightColorsParam;

        public DirectionalLightCollection(EffectParameter lightDirectionsParam, EffectParameter lightColorsParam)
        {
            this.lightDirectionsParam = lightDirectionsParam;
            this.lightColorsParam = lightColorsParam;
        }

        public DirectionalLight this[int i]
        {
            get
            {
                var color = colors[i] / intensities[i];
                return new DirectionalLight(
                    directions[i],
                    new Color(
                        color.X,
                        color.Y,
                        color.Z,
                        1f
                    ),
                    intensities[i]
                );
            }
            set
            {
                directions[i] = value.Direction;
                colors[i] = value.Color.ToVector3() * value.Intensity;
                intensities[i] = value.Intensity;
                lightDirectionsParam.SetValue(directions);
                lightColorsParam.SetValue(colors);
            }
        }
    }
}