/// <summary>
/// Fires a traceline and collects collision information.
/// </summary>
/// <param name="trace">Object containing the trace line parameters.</param>
/// <returns>
/// A value containing the result of the trace.
/// </returns>
public TraceResult TraceLine(TraceQuery trace)
{
double x0, y0, x1, y1;
List <GameEntity> entities = _entListPool.GetObject();
x0 = trace.Line.Start.X;
y0 = trace.Line.Start.Y;
x1 = trace.Line.End.X;
y1 = trace.Line.End.Y;
if ((trace.Options & TraceLineOptions.IgnoreEntities) == TraceLineOptions.None)
{
GetPossibleCollidersForTraceline(trace, entities);
}
var dx = Math.Abs(x1 - x0);
var dy = Math.Abs(y1 - y0);
int x = (int)Math.Floor(x0);
int y = (int)Math.Floor(y0);
int n = 1;
int x_inc, y_inc;
double error = 0.0D;
if (dx == 0)
{
x_inc = 0;
error = double.MaxValue;
}
else if (x1 > x0)
{
x_inc = 1;
n += (int)Math.Floor(x1) - x;
error = (Math.Floor(x0) + 1 - x0) * dy;
}
else
{
x_inc = -1;
n += x - (int)Math.Floor(x1);
error = (x0 - Math.Floor(x0)) * dy;
}
if (dy == 0)
{
y_inc = 0;
error -= double.MaxValue;
}
else if (y1 > y0)
{
y_inc = 1;
n += (int)Math.Floor(y1) - y;
error -= (Math.Floor(y0) + 1 - y0) * dx;
}
else
{
y_inc = -1;
n += y - (int)Math.Floor(y1);
error -= (y0 - Math.Floor(y0)) * dx;
}
var hit = false;
GeometryTile tile = null;
GameEntity entity = null;
for (; n > 0; --n)
{
// visit
if (entities.Count > 0)
{
hit = IsPointInEntity(entities, x, y, trace, out entity);
}
if (!hit && ((trace.Options & TraceLineOptions.IgnoreTiles) == TraceLineOptions.None))
{
hit = IsPointOnSolidTile(x, y, tile, trace, out tile);
}
if (hit)
{
break;
}
if (error > 0)
{
y += y_inc;
error -= dx;
}
else
{
x += x_inc;
error += dy;
}
}
if (_varShowTracelines.Value)
{
if (hit)
{
_renderService.DrawLine(new Line(trace.Line.Start.X, trace.Line.Start.Y, x, y), 0);
_renderService.DrawLine(new Line(x, y, trace.Line.End.X, trace.Line.End.Y), 0, 0, 255, 0);
}
else
{
_renderService.DrawLine(trace.Line, 0);
}
}
entities.Clear();
_entListPool.PutObject(entities);
var retval = new TraceResult();
retval.Hit = hit;
retval.ContactPoint = new Point(x, y);
retval.Entity = entity;
retval.Tile = tile;
return(retval);
}