//------------------------------------------------------
//
// Public Methods
//
//------------------------------------------------------
//------------------------------------------------------
//
// Public Properties
//
//------------------------------------------------------
//------------------------------------------------------
//
// Public Events
//
//------------------------------------------------------
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//
// Internal Methods
//
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#region Internal Methods
internal Matrix3D GetProjectionMatrix(double aspectRatio, double zn, double zf)
{
double fov = M3DUtil.DegreesToRadians(FieldOfView);
// Note: h and w are 1/2 of the inverse of the width/height ratios:
//
// h = 1/(heightDepthRatio) * (1/2)
// w = 1/(widthDepthRatio) * (1/2)
//
// Computation for h is a bit different than what you will find in
// D3DXMatrixPerspectiveFovRH because we have a horizontal rather
// than vertical FoV.
double halfWidthDepthRatio = Math.Tan(fov / 2);
double h = aspectRatio / halfWidthDepthRatio;
double w = 1 / halfWidthDepthRatio;
double m22 = zf != Double.PositiveInfinity ? zf / (zn - zf) : -1;
double m32 = zn * m22;
return(new Matrix3D(
w, 0, 0, 0,
0, h, 0, 0,
0, 0, m22, -1,
0, 0, m32, 0));
}
internal override RayHitTestParameters RayFromViewportPoint(Point p, Size viewSize, Rect3D boundingRect, out double distanceAdjustment)
{
// The camera may be animating. Take a snapshot of the current value
// and get the property values we need. (Window OS #992662)
Point3D position = Position;
Vector3D lookDirection = LookDirection;
Vector3D upDirection = UpDirection;
Transform3D transform = Transform;
double zn = NearPlaneDistance;
double zf = FarPlaneDistance;
double fov = M3DUtil.DegreesToRadians(FieldOfView);
//
// Compute rayParameters
//
// Find the point on the projection plane in post-projective space where
// the viewport maps to a 2x2 square from (-1,1)-(1,-1).
Point np = M3DUtil.GetNormalizedPoint(p, viewSize);
// Note: h and w are 1/2 of the inverse of the width/height ratios:
//
// h = 1/(heightDepthRatio) * (1/2)
// w = 1/(widthDepthRatio) * (1/2)
//
// Computation for h is a bit different than what you will find in
// D3DXMatrixPerspectiveFovRH because we have a horizontal rather
// than vertical FoV.
double aspectRatio = M3DUtil.GetAspectRatio(viewSize);
double halfWidthDepthRatio = Math.Tan(fov / 2);
double h = aspectRatio / halfWidthDepthRatio;
double w = 1 / halfWidthDepthRatio;
// To get from projective space to camera space we apply the
// width/height ratios to find our normalized point at 1 unit
// in front of the camera. (1 is convenient, but has no other
// special significance.) See note above about the construction
// of w and h.
Vector3D rayDirection = new Vector3D(np.X / w, np.Y / h, -1);
// Apply the inverse of the view matrix to our rayDirection vector
// to convert it from camera to world space.
//
// NOTE: Because our construction of the ray assumes that the
// viewMatrix translates the position to the origin we pass
// null for the Camera.Transform below and account for it
// later.
Matrix3D viewMatrix = CreateViewMatrix(/* trasform = */ null, ref position, ref lookDirection, ref upDirection);
Matrix3D invView = viewMatrix;
invView.Invert();
invView.MultiplyVector(ref rayDirection);
// The we have the ray direction, now we need the origin. The camera's
// position would work except that we would intersect geometry between
// the camera plane and the near plane so instead we must find the
// point on the project plane where the ray (position, rayDirection)
// intersect (Windows OS #1005064):
//
// | _.> p = camera position
// rd _+" ld = camera look direction
// .-" |ro pp = projection plane
// _.-" | rd = ray direction
// p +"--------+---> ro = desired ray origin on pp
// ld |
// pp
//
// Above we constructed the direction such that it's length projects to
// 1 unit on the lookDirection vector.
//
//
// rd _.>
// .-" rd = unnormalized rayDirection
// _.-" ld = normalized lookDirection (length = 1)
// -"--------->
// ld
//
// So to find the desired rayOrigin on the projection plane we simply do:
Point3D rayOrigin = position + zn * rayDirection;
rayDirection.Normalize();
// Account for the Camera.Transform we ignored during ray construction above.
if (transform != null && transform != Transform3D.Identity)
{
Matrix3D m = transform.Value;
m.MultiplyPoint(ref rayOrigin);
m.MultiplyVector(ref rayDirection);
PrependInverseTransform(m, ref viewMatrix);
}
RayHitTestParameters rayParameters = new RayHitTestParameters(rayOrigin, rayDirection);
//
// Compute HitTestProjectionMatrix
//
Matrix3D projectionMatrix = GetProjectionMatrix(aspectRatio, zn, zf);
// The projectionMatrix takes camera-space 3D points into normalized clip
// space.
// The viewportMatrix will take normalized clip space into
// viewport coordinates, with an additional 2D translation
// to put the ray at the rayOrigin.
Matrix3D viewportMatrix = new Matrix3D();
viewportMatrix.TranslatePrepend(new Vector3D(-p.X, viewSize.Height - p.Y, 0));
viewportMatrix.ScalePrepend(new Vector3D(viewSize.Width / 2, -viewSize.Height / 2, 1));
viewportMatrix.TranslatePrepend(new Vector3D(1, 1, 0));
// `First world-to-camera, then camera's projection, then normalized clip space to viewport.
rayParameters.HitTestProjectionMatrix =
viewMatrix *
projectionMatrix *
viewportMatrix;
//
// Perspective camera doesn't allow negative NearPlanes, so there's
// not much point in adjusting the ray origin. Hence, the
// distanceAdjustment remains 0.
//
distanceAdjustment = 0.0;
return(rayParameters);
}
