Kav/Effects/PointLightCollection.cs

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

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

        readonly EffectParameter lightPositionsParam;
        readonly EffectParameter lightColorsParam;

        public PointLightCollection(EffectParameter lightPositionsParam, EffectParameter lightColorsParam, int maxLights)
        {
            this.positions = new Vector3[maxLights];
            this.colors = new Vector3[maxLights];
            this.lightPositionsParam = lightPositionsParam;
            this.lightColorsParam = lightColorsParam;
        }

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