public void NextPoints(Point a, Point b)
{
Assert.AreEqual(b, poly.NextVertex(a));
}
public void CastShadow(ConvexPolygon poly, Vector2 position, bool penumbra)
{
// get the line that blocks light for the blocker and light combination
// move the light position towards blocker by its sourceradius to avoid
// popping of penumbrae
int[] edgeIndices = poly.GetBackfacingEdgeIndices((this.Position + Vector2.Multiply(Vector2.Normalize(position - this.Position), this.Size)) - position);
Vector2[] shadowLine = new Vector2[edgeIndices.Length + 1];
shadowLine[0] = position + poly[edgeIndices[0]];
for (int i = 0; i < edgeIndices.Length; i++)
shadowLine[i + 1] = position + poly.NextVertex(edgeIndices[i]);
// if the light source is completely surrounded by the blocker, don't draw its shadow
if (shadowLine.Length == poly.Count + 1)
return;
//
// build penumbrae (soft shadows), cast from the edges
//
Penumbra rightpenumbra;
{
Vector2 startdir = extendDir(shadowLine[0] - (this.Position - getLightDisplacement(position, shadowLine[0])));
rightpenumbra.sections = new List<Penumbra.Section>();
rightpenumbra.sections.Add(new Penumbra.Section(shadowLine[0], startdir, 0));
for (int i = 0; i < shadowLine.Length - 1; ++i)
{
float wanted = Math.Abs(MathUtils.AngleBetween(startdir, getTotalShadowStartDirection(position, shadowLine[i])));
float available = Math.Abs(MathUtils.AngleBetween(startdir, shadowLine[i + 1] - shadowLine[i]));
if (wanted < available)
{
rightpenumbra.sections.Add(new Penumbra.Section(
shadowLine[i],
getTotalShadowStartDirection(position, shadowLine[i]),
1));
break;
}
else
{
rightpenumbra.sections.Add(new Penumbra.Section(
shadowLine[i + 1],
extendDir(shadowLine[i + 1] - shadowLine[i]),
available / wanted));
}
}
}
Penumbra leftpenumbra;
{
Vector2 startdir = extendDir(shadowLine[shadowLine.Length - 1] - (this.Position - getLightDisplacement(position, shadowLine[shadowLine.Length - 1])));
leftpenumbra.sections = new List<Penumbra.Section>();
leftpenumbra.sections.Add(new Penumbra.Section(
shadowLine[shadowLine.Length - 1],
startdir,
0));
for (int i = 0; i < shadowLine.Length - 1; ++i)
{
float wanted = Math.Abs(MathUtils.AngleBetween(startdir, getTotalShadowStartDirection(position, shadowLine[shadowLine.Length - i - 1])));
float available = Math.Abs(MathUtils.AngleBetween(startdir, shadowLine[shadowLine.Length - i - 2] - shadowLine[shadowLine.Length - i - 1]));
if (wanted < available)
{
leftpenumbra.sections.Add(new Penumbra.Section(
shadowLine[shadowLine.Length - i - 1],
getTotalShadowStartDirection(position, shadowLine[shadowLine.Length - i - 1]),
1));
break;
}
else
{
leftpenumbra.sections.Add(new Penumbra.Section(
shadowLine[shadowLine.Length - i - 2],
extendDir(shadowLine[shadowLine.Length - i - 2] - shadowLine[shadowLine.Length - i - 1]),
available / wanted));
}
}
}
//
// build umbrae (hard shadows), cast between the insides of penumbrae
//
Umbra umbra;
umbra.sections = new List<Umbra.Section>();
umbra.sections.Add(new Umbra.Section(rightpenumbra.sections.Last()._base, rightpenumbra.sections.Last().direction));
for (int i = rightpenumbra.sections.Count - 1; i < shadowLine.Length - leftpenumbra.sections.Count + 1; i++)
umbra.sections.Add(new Umbra.Section(shadowLine[i], extendDir(Vector2.Multiply(leftpenumbra.sections.Last().direction + rightpenumbra.sections.Last().direction, 0.5f))));
umbra.sections.Add(new Umbra.Section(leftpenumbra.sections.Last()._base, leftpenumbra.sections.Last().direction));
//
// draw shadows to alpha
//
umbra.draw();
rightpenumbra.draw();
leftpenumbra.draw();
}
