/// <summary>
/// Defines the view matrix with an eye position, a look at point and an up vector.
/// This method is equivalent to the OpenGL function gluLookAt.
/// If Up is a zero vector a default up vector is calculated with a default
/// look-right vector (VZ) that lies in the x-z plane.
/// </summary>
/// <param name="Eye">Eye Vector to the position of the eye (view point)</param>
/// <param name="At">At Vector to the target point</param>
/// <param name="Up">Up Vector that points from the viewpoint upwards.</param>
public void LookAt(SLVec3f Eye, SLVec3f At, SLVec3f Up)
{
SLVec3f VX, VY, VZ, VT, ZERO;
//SLMat3<T> xz(0.0, 0.0, 1.0, // matrix that transforms YZ into a
// 0.0, 0.0, 0.0, // vector that is perpendicular to YZ and
// -1.0, 0.0, 0.0); // lies in the x-z plane
VZ = Eye - At;
VZ.Normalize();
VX = new SLVec3f();
ZERO = new SLVec3f();
if (Up == ZERO)
{
VX.x = VZ.z;
VX.y = 0;
VX.z = -1 * VZ.x;
}
else
{
VX = Up.Cross(VZ);
}
VY = SLVec3f.CrossProduct(VZ, VX);
VX.Normalize();
VY.Normalize();
VZ.Normalize();
VT = -Eye;
Set(VX.x, VX.y, VX.z, SLVec3f.DotProduct(VX, VT),
VY.x, VY.y, VY.z, SLVec3f.DotProduct(VY, VT),
VZ.x, VZ.y, VZ.z, SLVec3f.DotProduct(VZ, VT),
0.0f, 0.0f, 0.0f, 1.0f);
}
/// <summary>
/// if vertecies are in inverse order or not
/// </summary>
/// <param name="v0">vertex 1</param>
/// <param name="v1">vertex 2</param>
/// <param name="v2">vertex 3</param>
/// <param name="cam">relative to the camera position</param>
/// <returns></returns>
private bool backfaceCulling(SLVertex v0, SLVertex v1, SLVertex v2, SLVec3f cam)
{
SLVec3f face = SLVec3f.CrossProduct((v1.position - v0.position), (v2.position - v0.position));
return(SLVec3f.DotProduct(face, cam) >= 0 || xWireframeActive);
}