IsometricMath

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;

namespace IsometricMath
{
    class IsometricGrid
    {
        public void updateMouseover(int x, int y)
        {
            int rX = (x - _origin.X);
            int rY = (y - _origin.Y);

            double det = _xAxis.X * _yAxis.Y - _xAxis.Y * _yAxis.X;
            _mouseOver = new Point((int)Math.Floor((_yAxis.Y * rX - _yAxis.X * rY) / det), (int)Math.Floor((-_xAxis.Y * rX + _xAxis.X * rY) / det));
        }

        public void drawGrid(Graphics g)
        {
            using (Pen pen = new Pen(Color.Black))
            {
                for (int i = 0; i < GRID_SIZE.X + 1; ++i)
                {
                    Point lineStart = isoToScreen(i, 0);
                    Point lineEnd = isoToScreen(i, GRID_SIZE.Y);
                    g.DrawLine(pen, lineStart, lineEnd);
                }

                for (int i = 0; i < GRID_SIZE.Y + 1; ++i)
                {
                    Point lineStart = isoToScreen(0, i);
                    Point lineEnd = isoToScreen(GRID_SIZE.X, i);
                    g.DrawLine(pen, lineStart, lineEnd);
                }

                using (Font font = new Font("Arial", 8.0f))
                {
                    using (Brush brush = new SolidBrush(Color.Black))
                    {
                        for (int y = 0; y < GRID_SIZE.Y; ++y)
                        {
                            for (int x = 0; x < GRID_SIZE.X; ++x)
                            {
                                Point p = isoToScreen(x, y + 0.5);
                                g.DrawString(string.Format("{2}({0},{1}){2}", x, y, ((x==_mouseOver.X) && (y==_mouseOver.Y)) ? "*" : ""), font, brush, p.X, p.Y);
                            }
                        }
                    }
                }
            }
        }

        public Point Origin
        {
            get { return _origin; }
            set { _origin = value; }
        }

        public float TileWidth
        {
            get { return _tileWidth; }
            set { _tileWidth = value; updateAxis(); }
        }

        public float TileHeight
        {
            get { return _tileHeight; }
            set { _tileHeight = value; updateAxis(); }
        }

        private void updateAxis()
        {
            _xAxis = new PointF(_tileWidth / 2.0f, _tileHeight / 2.0f);
            _yAxis = new PointF(_tileWidth / 2.0f, -_tileHeight / 2.0f);
        }

        private Point isoToScreen(double x, double y)
        {
            return new Point((int)((_xAxis.X * x + _yAxis.X * y) + _origin.X), (int)((_xAxis.Y * x + _yAxis.Y * y) + _origin.Y));
        }

        private Point _origin = new Point(0, 0);
        private float _tileWidth = 1;
        private float _tileHeight = 1;
        private PointF _xAxis = new PointF(0.5f, 0.5f);
        private PointF _yAxis = new PointF(0.5f, -0.5f);
        private Point _mouseOver = new Point(0, 0);

        private Point GRID_SIZE = new Point(15, 15);
    }
}