public Triangle[] CreateScreenSpaceLines(Point3D begin, Point3D end, double thickness, Color color)
{
VerticesBehindCamera behind = VerticesBehindCamera.None;
if (begin.Z >= 0)
{
behind |= VerticesBehindCamera.Vertex1;
}
if (end.Z >= 0)
{
behind |= VerticesBehindCamera.Vertex2;
}
switch (behind)
{
case VerticesBehindCamera.Vertex1:
{
// 'begin' is behind the camera. Replace it with a new point that isn't.
Weights weights = Interpolator.GetWeightsToXYPlane(begin, end, -distanceAheadOfCamera);
begin = Interpolator.WeightedSum(begin, end, weights);
break;
}
case VerticesBehindCamera.Vertex2:
{
// 'end' is behind the camera. Replace it with a new point that isn't.
Weights weights = Interpolator.GetWeightsToXYPlane(begin, end, -distanceAheadOfCamera);
end = Interpolator.WeightedSum(begin, end, weights);
break;
}
case VerticesBehindCamera.Vertex1And2:
return(new Triangle[0]);
default:
break;
}
return(new Triangle[] { new ScreenSpaceLineTriangle(begin, end, thickness, color, projection),
new ScreenSpaceLineTriangle(end, begin, thickness, color, projection) });
}
private void ReorderVertices(ref Vertex v1, ref Vertex v2, ref Vertex v3, VerticesBehindCamera behind)
{
Vertex temp = null;
switch (behind)
{
case VerticesBehindCamera.None:
case VerticesBehindCamera.AllVertices:
case VerticesBehindCamera.Vertex1:
case VerticesBehindCamera.Vertex1And2:
// Do nothing
break;
case VerticesBehindCamera.Vertex2:
case VerticesBehindCamera.Vertex2And3:
// Rotate CCW
temp = v1;
v1 = v2;
v2 = v3;
v3 = temp;
break;
case VerticesBehindCamera.Vertex3:
case VerticesBehindCamera.Vertex1And3:
// Rotate CW
temp = v1;
v1 = v3;
v3 = v2;
v2 = temp;
break;
}
}
public Triangle[] CreateTriangles(Vertex v1, Vertex v2, Vertex v3)
{
VerticesBehindCamera behind = VerticesBehindCamera.None;
if (v1.PositionZ >= 0)
{
behind |= VerticesBehindCamera.Vertex1;
}
if (v2.PositionZ >= 0)
{
behind |= VerticesBehindCamera.Vertex2;
}
if (v3.PositionZ >= 0)
{
behind |= VerticesBehindCamera.Vertex3;
}
// Set v1 (and possibly v2) as the clipped vertex (vertices)
// We do this to simplify the tessellation code (in the 'switch' block below)
ReorderVertices(ref v1, ref v2, ref v3, behind);
switch (behind)
{
case VerticesBehindCamera.Vertex1:
case VerticesBehindCamera.Vertex2:
case VerticesBehindCamera.Vertex3:
{
// The two triangles created are 2-3-4 and 2-4-5
// Vertices 4 and 5 are actually just in front of the camera plane (unlike the picture shows)
//
// 3---------2 ^ camera look direction
// \ ." / |
// \ ." / |
// <-----4---5-------> camera plane (NOT the near clipping plane)
// \ /
// 1 behind the camera
//
Vertex v4 = GetVertexAheadOfCamera(v1, v3);
Vertex v5 = GetVertexAheadOfCamera(v1, v2);
return new Triangle[]{ new Triangle( v2, v3, v4, projection ),
new Triangle( v2, v4, v5, projection ) };
}
case VerticesBehindCamera.Vertex1And2:
case VerticesBehindCamera.Vertex1And3:
case VerticesBehindCamera.Vertex2And3:
{
// The triangle created is 3-4-5
// Vertices 4 and 5 are actually just in front of the camera plane (unlike the picture shows)
//
// 3 ^ camera look direction
// / \ |
// / \ |
// <----4-----5------> camera plane (NOT the near clipping plane)
// / \
// 1---------2 behind the camera
Vertex v4 = GetVertexAheadOfCamera(v1, v3);
Vertex v5 = GetVertexAheadOfCamera(v2, v3);
return new Triangle[] { new Triangle(v3, v4, v5, projection) };
}
case VerticesBehindCamera.AllVertices:
return new Triangle[0];
case VerticesBehindCamera.None:
default:
return new Triangle[] { new Triangle(v1, v2, v3, projection) };
}
}
