Visualization - get rid of projection shift from orthographic camera definition

The projection shift concept was removed. The reference system of the view is now located at the center of screen, in consistence with definition rules of a camera. There is no more Center property of V3d_View, which was originally used to specify shift of projection matrix and to slide reference system of the view along the screen.

This improvement has effect on panning and turning behavior of V3d_View. The panning is now performed by sliding location of V3d_View: At, Eye. The turning around reference system of the view is done as usually, except that the reference system is now located in center of the view.

Fit all operation was modified in order to support perspective projection. The low-level implementation of the operation is now used by both V3d_View and NIS_View. The core behavior of fit all is now unified for these classes, however the principal differences are kept untouched.

There are several changes introduced to Graphic3d_Camera. The internal data structures of the camera is based on Standard_Real data types to avoid redundant application-level conversions and precision errors. The transformation matrices are now can be evaluated both for Standard_Real and Standard_ShortReal value types. The ZNear and ZFar planes can be both negative or positive for orthographic camera projection, providing a trade-off between camera distance and range of ZNear, ZFar in order to reduce difference of exponents of values composing the orientation matrix - to avoid calculation errors. The negative values can be specified to avoid Z-clipping if the reference system of camera goes inside of the model when decreasing camera distance.

The auto z fit mode, since now, has a parameter defining Z-range margin (the one which is usually passed as argument to ZFitAll() method). The V3d_View SetAutoZFitMode(), AutoZFitScaleFactor(), ZFitAll() methods deals with the new parameter.

The code of Select3D_Projector class has been revised. It supports both orientation and projection transformation matrices, which can be naturally set for the projector. The definition of projector was revised in StdSelect_ViewerSelector3d: perspective and orthographic projection parameters are handled properly. Orthographic projector is based only on direction of projection - no more Center property. This makes possible to avoid unnecessary re-projection of sensitives while panning, zooming or moving along the projection ray of the view. These operations do not affect the orthographic projection.

List of changes:

V3d_View

- Center() has been removed. SetCenter() method now changes relative location of the center of screen.
- Panning now translates At, Eye position of the view along the view plane.
- SetViewingVolume() has been removed. The same modifications to viewing volume can be done via camera of the view (Camera()).
- Duplicating method Zoom (CurrX, CurrY) has been removed. The method Zoom (FromX, FromY, ToX, ToY) should be used instead.
- SetAutoZFitMode(), AutoZFitScaleFactor(), ZFitAll() deal with new parameter: Z-range margin.
- Turn() method now performs rotation around view reference system, which is located at center of the screen (around screen axes). Center() has no effect anymore. To produce similar rotation to the previous one, the effect of Center() can be introduced by rotating view around a point with Rotate() method.

Graphic3d_Camera

- ProjectionShift(), SetProjectionShift() are removed.
- SetZNear(), SetZFar() have been replaced by unified SetZRange() method. ZNear, ZFar can be negative for orthographic camera.
- BeginUpdate(), EndUpdate() methods have been replaced by matrix lazy-computation approach. There is no necessity in these methods anymore.
- WindowLimit() method is removed - is redundant. The method had the same meaning as ViewDimensions(), summed up with ProjectionShift().
- ViewDimension(), AxialScale() - type of argument is changed from gp_Pnt to gp_XYZ.

Select3D_Projector

- Added methods to defined both view-transformation and projection-transformation matrices.
- The projector now contains constant projection / orientation state. Previously it was possible to pass handle on the view, so the Project() method was giving projection results for actual view projection. However, the same handle was not used for other projector methods: Transform(), Transformation().
- SetView() instead of saving reference on the passed view, captures current state of its projection / orientation matrices.

Porting notes:

It might be necessary to revise code of the application, which deals with Center() method of V3d_View. The Center() was used to pan V3d view by virtually moving center of the screen with respect to projection ray passed through Eye and At points. There is no more need to derive the panning from the Center parameter in order to get camera-like position of eye and look at coordinates. The Eye(), At() now returns these coordinates directly. When porting code dealing with Center(), the Eye() and At() could be adjusted instead. The behavior of Turn(), Panning(), Pan() view operations is changed. Please refer to "List of changes" for more details.