public VisibilityCheck(World world)
{
this.world = world;
trace = new DivLine();
occluder = new DivLine();
}
/// <summary>
/// Calculate on which side of the line the point is.
/// </summary>
/// <returns>
/// 0 (front) or 1 (back).
/// </returns>
public static int PointOnDivLineSide(Fixed x, Fixed y, DivLine line)
{
if (line.Dx == Fixed.Zero)
{
if (x <= line.X)
{
return(line.Dy > Fixed.Zero ? 1 : 0);
}
else
{
return(line.Dy < Fixed.Zero ? 1 : 0);
}
}
if (line.Dy == Fixed.Zero)
{
if (y <= line.Y)
{
return(line.Dx < Fixed.Zero ? 1 : 0);
}
else
{
return(line.Dx > Fixed.Zero ? 1 : 0);
}
}
var dx = (x - line.X);
var dy = (y - line.Y);
// Try to quickly decide by looking at sign bits.
if (((line.Dy.Data ^ line.Dx.Data ^ dx.Data ^ dy.Data) & 0x80000000) != 0)
{
if (((line.Dy.Data ^ dx.Data) & 0x80000000) != 0)
{
// Left is negative.
return(1);
}
else
{
return(0);
}
}
var left = new Fixed(line.Dy.Data >> 8) * new Fixed(dx.Data >> 8);
var right = new Fixed(dy.Data >> 8) * new Fixed(line.Dx.Data >> 8);
if (right < left)
{
// Front side.
return(0);
}
else
{
// Back side.
return(1);
}
}
/// <summary>
/// Calculate on which side of the line the point is.
/// </summary>
/// <returns>
/// 0 (front) or 1 (back), or 2 if the box crosses the line.
/// </returns>
public static int DivLineSide(Fixed x, Fixed y, DivLine line)
{
if (line.Dx == Fixed.Zero)
{
if (x == line.X)
{
return(2);
}
if (x <= line.X)
{
return(line.Dy > Fixed.Zero ? 1 : 0);
}
return(line.Dy < Fixed.Zero ? 1 : 0);
}
if (line.Dy == Fixed.Zero)
{
if (x == line.Y)
{
return(2);
}
if (y <= line.Y)
{
return(line.Dx < Fixed.Zero ? 1 : 0);
}
return(line.Dx > Fixed.Zero ? 1 : 0);
}
var dx = (x - line.X);
var dy = (y - line.Y);
var left = new Fixed((line.Dy.Data >> Fixed.FracBits) * (dx.Data >> Fixed.FracBits));
var right = new Fixed((dy.Data >> Fixed.FracBits) * (line.Dx.Data >> Fixed.FracBits));
if (right < left)
{
// Front side.
return(0);
}
if (left == right)
{
return(2);
}
else
{
// Back side.
return(1);
}
}
private Fixed InterceptVector(DivLine v2, DivLine v1)
{
var den = (v1.Dy >> 8) * v2.Dx - (v1.Dx >> 8) * v2.Dy;
if (den == Fixed.Zero)
{
return(Fixed.Zero);
}
var num = ((v1.X - v2.X) >> 8) * v1.Dy + ((v2.Y - v1.Y) >> 8) * v1.Dx;
var frac = num / den;
return(frac);
}
public PathTraversal(World world)
{
this.world = world;
intercepts = new Intercept[256];
for (var i = 0; i < intercepts.Length; i++)
{
intercepts[i] = new Intercept();
}
target = new DivLine();
trace = new DivLine();
lineInterceptFunc = AddLineIntercepts;
thingInterceptFunc = AddThingIntercepts;
}
