MonoGame.Extended/source/MonoGame.Extended.Particles/Profiles/BoxUniformProfile.cs

using Microsoft.Xna.Framework;

namespace MonoGame.Extended.Particles.Profiles
{
    public class BoxUniformProfile : Profile
    {
        public float Width { get; set; }
        public float Height { get; set; }

        public override void GetOffsetAndHeading(out Vector2 offset, out Vector2 heading)
        {
            var value = Random.Next((int) (2*Width + 2*Height));

            if (value < Width) // Top
                offset = new Vector2(Random.NextSingle(Width*-0.5f, Width*0.5f), Height*-0.5f);
            else
            {
                if (value < 2*Width) // Bottom
                    offset = new Vector2(Random.NextSingle(Width*-0.5f, Width*0.5f), Height*0.5f);
                else
                {
                    if (value < 2*Width + Height) // Left
                        offset = new Vector2(Width*-0.5f, Random.NextSingle(Height*-0.5f, Height*0.5f));
                    else // Right
                        offset = new Vector2(Width*0.5f, Random.NextSingle(Height*-0.5f, Height*0.5f));
                }
            }

            Random.NextUnitVector(out heading);
        }
    }
}