void OnCanvasViewPaintSurface(object sender, SKPaintSurfaceEventArgs args)
{
SKImageInfo info = args.Info;
SKSurface surface = args.Surface;
SKCanvas canvas = surface.Canvas;
canvas.Clear();
// From orientation quaternion, get view center in horizontal coordinates
Matrix4x4 matrix = Matrix4x4.CreateFromQuaternion(orientation);
HorizontalCoordinate viewCenter = HorizontalCoordinate.FromRotationMatrix(matrix);
coordinateProjection.SetViewCenter(viewCenter);
// Rotate for Tilt
canvas.RotateDegrees((float)-viewCenter.Tilt, info.Width / 2, info.Height / 2);
// Draw aximuth lines
for (double azimuth = 0; azimuth < 360; azimuth += 15)
{
for (double altitude = -90; altitude < 90; altitude += 15)
{
HorizontalCoordinate coord1 = new HorizontalCoordinate(azimuth, altitude);
HorizontalCoordinate coord2 = new HorizontalCoordinate(azimuth, altitude + 15);
SKPoint point1 = CalculateScreenPoint(coord1, info.Width, info.Height);
SKPoint point2 = CalculateScreenPoint(coord2, info.Width, info.Height);
if (!double.IsNaN(point1.X) && !double.IsNaN(point2.X))
{
canvas.DrawLine(point1, point2, linePaint);
}
}
}
// Draw altitude lines
for (double altitude = -75; altitude < 90; altitude += 15)
{
for (double azimuth = 0; azimuth < 360; azimuth += 15)
{
HorizontalCoordinate coord1 = new HorizontalCoordinate(azimuth, altitude);
HorizontalCoordinate coord2 = new HorizontalCoordinate(azimuth + 15, altitude);
SKPoint point1 = CalculateScreenPoint(coord1, info.Width, info.Height);
SKPoint point2 = CalculateScreenPoint(coord2, info.Width, info.Height);
if (!double.IsNaN(point1.X) && !double.IsNaN(point2.X))
{
canvas.DrawLine(point1, point2, linePaint);
}
}
}
// Draw text for altitude angles
for (double altitude = -75; altitude < 90; altitude += 15)
{
HorizontalCoordinate coord = new HorizontalCoordinate(viewCenter.Azimuth, altitude);
SKPoint point = CalculateScreenPoint(coord, info.Width, info.Height);
textPaint.TextAlign = SKTextAlign.Center;
canvas.DrawText(altitude == 0 ? "Equator" : (altitude.ToString() + '\xB0'), point, textPaint);
}
// Draw text for azimuth compass points
for (double azimuth = 0; azimuth < 360; azimuth += 45)
{
double altitude = Math.Min(80, Math.Max(-80, viewCenter.Altitude));
HorizontalCoordinate coord = new HorizontalCoordinate(azimuth, altitude);
SKPoint point = CalculateScreenPoint(coord, info.Width, info.Height);
textPaint.TextAlign = SKTextAlign.Left;
canvas.DrawText(compass[(int)(azimuth / 45)], point, textPaint);
}
}