KDE API Referencekstars
#include <projector.h>
Public Member Functions | |
| Projector (const ViewParams &p) | |
| virtual | ~Projector () |
| bool | checkVisibility (SkyPoint *p) const |
| QPointF | clipLine (SkyPoint *p1, SkyPoint *p2) const |
| Vector2f | clipLineVec (SkyPoint *p1, SkyPoint *p2) const |
| double | findPA (SkyObject *o, float x, float y) const |
| double | fov () const |
| virtual SkyPoint | fromScreen (const QPointF &p, dms *LST, const dms *lat) const |
| virtual QVector< Vector2f > | groundPoly (SkyPoint *labelpoint=0, bool *drawLabel=0) const |
| bool | onScreen (const QPointF &p) const |
| bool | onScreen (const Vector2f &p) const |
| void | setViewParams (const ViewParams &p) |
| QPointF | toScreen (const SkyPoint *o, bool oRefract=true, bool *onVisibleHemisphere=0) const |
| virtual Vector2f | toScreenVec (const SkyPoint *o, bool oRefract=true, bool *onVisibleHemisphere=0) const |
| virtual SkyMap::Projection | type () const =0 |
| virtual bool | unusablePoint (const QPointF &p) const |
Protected Member Functions | |
| virtual double | cosMaxFieldAngle () const |
| virtual double | projectionK (double x) const |
| virtual double | projectionL (double x) const |
| virtual double | radius () const |
Static Protected Member Functions | |
| static SkyPoint | pointAt (double az, KStarsData *data) |
Protected Attributes | |
| double | m_cosY0 |
| KStarsData * | m_data |
| double | m_fov |
| double | m_sinY0 |
| ViewParams | m_vp |
Detailed Description
This class serves as an interface to handle projections.
Definition at line 49 of file projector.h.
Constructor & Destructor Documentation
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explicit |
Constructor.
- Parameters
-
p the ViewParams for this projection
Definition at line 49 of file projector.cpp.
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virtual |
Definition at line 55 of file projector.cpp.
Member Function Documentation
| bool Projector::checkVisibility | ( | SkyPoint * | p | ) | const |
Determine if the skypoint p is likely to be visible in the display window.
checkVisibility() is an optimization function. It determines whether an object appears within the bounds of the skymap window, and therefore should be drawn. The idea is to save time by skipping objects which are off-screen, so it is absolutely essential that checkVisibility() is significantly faster than the computations required to draw the object to the screen.
If the ground is to be filled, the function first checks whether the point is below the horizon, because they will be covered by the ground anyways. Importantly, it does not call the expensive EquatorialToHorizontal function. This means that the horizontal coordinates MUST BE CORRECT! The vast majority of points are already synchronized, so recomputing the horizontal coordinates is a waste.
The function then checks the difference between the Declination/Altitude coordinate of the Focus position, and that of the point p. If the absolute value of this difference is larger than fov, then the function returns false. For most configurations of the sky map window, this simple check is enough to exclude a large number of objects.
Next, it determines if one of the poles of the current Coordinate System (Equatorial or Horizontal) is currently inside the sky map window. This is stored in the member variable 'bool SkyMap::isPoleVisible, and is set by the function SkyMap::setMapGeometry(), which is called by SkyMap::paintEvent(). If a Pole is visible, then it will return true immediately. The idea is that when a pole is on-screen it is computationally expensive to determine whether a particular position is on-screen or not: for many valid Dec/Alt values, all values of RA/Az will indeed be onscreen, but for other valid Dec/Alt values, only most RA/Az values are onscreen. It is cheaper to simply accept all "horizontal" RA/Az values, since we have already determined that they are on-screen in the "vertical" Dec/Alt coordinate.
Finally, if no Pole is onscreen, it checks the difference between the Focus position's RA/Az coordinate and that of the point p. If the absolute value of this difference is larger than XMax, the function returns false. Otherwise, it returns true.
- Parameters
-
p pointer to the skypoint to be checked.
- Returns
- true if the point p was found to be inside the Sky map window.
- See also
- SkyMap::setMapGeometry()
- SkyMap::fov()
- Note
- If you are creating skypoints using equatorial coordinates, then YOU MUST CALL EQUATORIALTOHORIZONTAL BEFORE THIS FUNCTION!
To avoid calculating refraction, we just use the unrefracted altitude and add a 2-degree 'safety factor'
Definition at line 181 of file projector.cpp.
ASSUMES *p1 did not clip but *p2 did.
Returns the QPointF on the line between *p1 and *p2 that just clips.
Definition at line 110 of file projector.cpp.
ASSUMES *p1 did not clip but *p2 did.
Returns the Vector2f on the line between *p1 and *p2 that just clips.
Definition at line 115 of file projector.cpp.
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inlineprotectedvirtual |
This function returns the cosine of the maximum field angle, i.e., the maximum angular distance from the focus for which a point should be projected.
Default is 0, i.e., 90 degrees.
Reimplemented in GnomonicProjector.
Definition at line 219 of file projector.h.
| double Projector::findPA | ( | SkyObject * | o, |
| float | x, | ||
| float | y | ||
| ) | const |
Determine the on-screen position angle of a SkyObject.
This is the sum of the object's sky position angle (w.r.t. North), and the position angle of "North" at the position of the object (w.r.t. the screen Y-axis). The latter is determined by constructing a test point with the same RA but a slightly increased Dec as the object, and calculating the angle w.r.t. the Y-axis of the line connecing the object to its test point.
Definition at line 227 of file projector.cpp.
| double Projector::fov | ( | ) | const |
Return the FOV of this projection.
Definition at line 88 of file projector.cpp.
Determine RA, Dec coordinates of the pixel at (dx, dy), which are the screen pixel coordinate offsets from the center of the Sky pixmap.
- Parameters
-
the screen pixel position to convert LST pointer to the local sidereal time, as a dms object. lat pointer to the current geographic laitude, as a dms object
N.B. We don't cache these sin/cos values in the inverse projection because it causes 'shaking' when moving the sky.
Reimplemented in EquirectangularProjector.
Definition at line 353 of file projector.cpp.
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virtual |
Get the ground polygon.
- Parameters
-
labelpoint This point will be set to something suitable for attaching a label drawLabel this tells whether to draw a label.
- Returns
- the ground polygon
Reimplemented in EquirectangularProjector.
Definition at line 252 of file projector.cpp.
| bool Projector::onScreen | ( | const QPointF & | p | ) | const |
Check whether the projected point is on-screen.
Definition at line 98 of file projector.cpp.
| bool Projector::onScreen | ( | const Vector2f & | p | ) | const |
Definition at line 104 of file projector.cpp.
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staticprotected |
Helper function for drawing ground.
- Returns
- the point with Alt = 0, az =
az
Definition at line 40 of file projector.cpp.
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inlineprotectedvirtual |
This function handles some of the projection-specific code.
- See also
- toScreen()
Reimplemented in LambertProjector, AzimuthalEquidistantProjector, GnomonicProjector, OrthographicProjector, and StereographicProjector.
Definition at line 207 of file projector.h.
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inlineprotectedvirtual |
This function handles some of the projection-specific code.
- See also
- toScreen()
Reimplemented in LambertProjector, AzimuthalEquidistantProjector, GnomonicProjector, OrthographicProjector, and StereographicProjector.
Definition at line 212 of file projector.h.
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inlineprotectedvirtual |
Get the radius of this projection's sky circle.
- Returns
- the radius in radians
Reimplemented in LambertProjector, AzimuthalEquidistantProjector, GnomonicProjector, OrthographicProjector, StereographicProjector, and EquirectangularProjector.
Definition at line 202 of file projector.h.
| void Projector::setViewParams | ( | const ViewParams & | p | ) |
Update cached values for projector.
Precompute cached values
Definition at line 60 of file projector.cpp.
| QPointF Projector::toScreen | ( | const SkyPoint * | o, |
| bool | oRefract = true, |
||
| bool * | onVisibleHemisphere = 0 |
||
| ) | const |
This is exactly the same as toScreenVec but it returns a QPointF.
It just calls toScreenVec and converts the result.
- See also
- toScreenVec()
Definition at line 93 of file projector.cpp.
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virtual |
Given the coordinates of the SkyPoint argument, determine the pixel coordinates in the SkyMap.
Since most of the projections used by KStars are very similar, if this function were to be reimplemented in each projection subclass we would end up changing maybe 5 or 6 lines out of 150. Instead, we have a default implementation that uses the projectionK and projectionL functions to take care of the differences between e.g. Orthographic and Stereographic. There is also the cosMaxFieldAngle function, which is used for testing whether a point is on the visible part of the projection, and the radius function which gives the radius of the projection in screen coordinates.
While this seems ugly, it is less ugly than duplicating 150 loc to change 5.
- Returns
- Vector2f containing screen pixel x, y coordinates of SkyPoint.
- Parameters
-
o pointer to the SkyPoint for which to calculate x, y coordinates. oRefract true = use Options::useRefraction() value. false = do not use refraction. This argument is only needed for the Horizon, which should never be refracted. onVisibleHemisphere pointer to a bool to indicate whether the point is on the visible part of the Celestial Sphere.
Reimplemented in EquirectangularProjector.
Definition at line 402 of file projector.cpp.
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pure virtual |
Return the type of this projection.
Implemented in LambertProjector, AzimuthalEquidistantProjector, GnomonicProjector, OrthographicProjector, StereographicProjector, and EquirectangularProjector.
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virtual |
Check if the current point on screen is a valid point on the sky.
This is needed to avoid a crash of the program if the user clicks on a point outside the sky (the corners of the sky map at the lowest zoom level are the invalid points).
- Parameters
-
p the screen pixel position
Reimplemented in EquirectangularProjector.
Definition at line 338 of file projector.cpp.
Member Data Documentation
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protected |
Definition at line 228 of file projector.h.
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protected |
Definition at line 226 of file projector.h.
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Definition at line 229 of file projector.h.
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Definition at line 228 of file projector.h.
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Definition at line 227 of file projector.h.
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