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Two Dimensional Views (Pure 2D)

Two Dimensional Mode of DG Kernel components allow displaying items which are two dimensional by its nature, namely sets of lines, points and 2D shapes.

Two Dimensional view (2D View) keeps internally a 2D item set, which is a 2D analogue of 3D model. Although 2D set is often generated from 3D model of the component it can be completely independent.

Use IView2.SetViewType to switch between two and three dimensional modes of the component. 2D View functionality is controlled via I2DView_KC Interface, which cal be obtained via: DG Kernel > GetView > IView > I2DView_KC

2D Views have number of properties (see the table below), which define how the items are displayed. Programmatically these properties can be managed via IKCContext queried from the I2DView_KC.

2D Views have also a 3D frame associated with it. The frame is called Frame of 2D View. It is used for mapping between 2D coordinates of the view and 3D coordinates of the main model.  x and y plane of the frame is called plane of the view. The frame, hence position and orientation of the plane can be set arbitrary via IFrame and other related frame interfaces queried from the IKCContext.

There are two ways to add 2D items to the 2D item set:

1. 2D Mapping

With this method 2D items are generated by mapping 3D objects of the main model of the component to 2D coordinate axes and adding the results to the 2D scene automatically. Currently there are two methods of mapping:  interentity and projection.

2D mapping is very useful for displaying planar entitys of objects or projections to a plane It requires minimal programming.

Both methods use frame of the view (see above) to define the plane on which the image is generated and orientation of 2D axes inside the plane. 2D x and y axes are x and y axes of the frame of view.

With interentity mapping each object of the 3D model is intersected with plane of the view (see above). If interentity is not empty interentity line is mapped to local x and y coordinates of the frame of view and added to 2D scene as a new item.

With projection mapping each object of the 3D model is projected to the plane of the view. The result will look as if the 3D point of view has changed so that the viewer is looking along negative direction of z axis of the frame of view and y axis is up.

The projection  works on per patch basis. A 3D patch is projected as a polygon (curvilinear in general case) rendered as line loop of its edge. When hidden line removal is enabled (default) lines which are covered by a higher polygon (the 3D edge from which the line was projected is invisible in 3D from end of z axis of the frame of view) are removed. Projected lines are mapped to local x and y coordinates of the frame of view and added to 2D scene as a new item.

The above work is performed during UpdateSurface call. when view type is set to 2D.

2D items keep information about its z position along z axis of the frame of view.

To use 2D Mapping mode:

1. Set view type to 2D with IView2.SetViewType(EViewType.eViewType2D)
2. Query I2DView_KC via: DG Kernel > GetView > IView > I2DView_KC
3. Obtain IKCContext via I2DView_KC.GetContext.
4. Set required mapping type with IKCContext.SetIntParam(0, E2DViewGeometryType.e2DViewGeometryTypeInterentity ) or IKCContext.SetIntParam(0, E2DViewGeometryType.e2DViewGeometryTypeProjection )
5. Use IFrame or/and IFrame2 queried from the IKCContext. to set position and orientation of the plane of the view and x, y axes inside the plane.
6. Call UpdateSurface to create the 2D items and display them in the view

See Cross View Sample for an example.

2. Direct Definition

With Direct Definition method 2D items are defined and added to the scene directly without any reference to any 3D objects.

To use Direct Definition mode:

1. Set view type to 2D with IView2.SetViewType(EViewType.eViewType2D)
2. Query IKCContext via: DG Kernel > GetView > IView > I2DView_KC > IKCContext
3. Query IDraw from IKCContext.
4. Use IDraw.Begin, IDraw.Vertex, IDraw.End to add lines, points or shapes to the 2D item set. Use I2DView_KC.AddText to add text stings at specified locations
5. Use I2DView_KC.AddText to add text strings
6. Call UpdateView to redraw the window

Note that IDraw is used here in an unusual way. Instead of normal drawing of a single scene it is used to define geometry, which will be used in multiple rendering with possible window resizing, etc.

See MidImplementation.AddProjection() method of Cross View Sample for an example.

Both 2D Mapping and Direct Definition methods can be used simultaneously. So that 2D view can contain items generated both by 2D mapping and items created directly.

Use I2DView_KC.RemoveAll to remove all items from the View.

Often 2D mode is used to show a model in multiple projections. This can be achieved by using External models.

When ShowAngles property is true the view displays text strings with angles in degrees inside narrowest corners of 2D polygons. Angles 0, 90, and 180 are not displayed. This functionality is useful mostly when objects have straight edges in 3D. Font of the text can be modified by queering IDIFont from the return of IKCContext.GetParam(0), See ChildrenFont in the table below

When ShowRulersOrGrid property is true either grid or vertical and horizontal rulers showing dimensions of the object(s) are displayed. Font of dimensions can be modified by queering IDIFont from the return of IKCContext.GetParam(1), See DimensionsFont in the table below.

When rules are on and the 2D items are very long in one direction the scene is displayed with a break in the middle to use space of the window more efficiently.. Use BreakLongDimension property to disable this functionality.

When ShowSideAnnotation property is true and frame of the view is aligned with global axes, more exactly orientation of the frame of the view coincides with orientation of the global frame rotated one or more times around its axes by 90 degrees, "Front", "Left", etc text will be displayed at the top left corner of the view. Font of the annotation can be modified by queering IDIFont from the return of IKCContext.GetParam(2), See SideAnnotationFont in the table below.

2D Views can be printed using IPrint_KC obtained via: DG Kernel > GetView > IView > IPrint_KC.

Properties of 2D View accessed via IKCContext

Properties of 2D View accessed via IKCContext2

Programmatic 2D Zoom

HorVisibleRange and VertVisibleRange properties provide programmatic access to viewing rectangle of the displayed scene of a 2D view.

For example, increasing length of the horizontal range will result in large area of 2D plane to be displayed in the current window so the model will appear smaller, which has effect of zooming out. Reduction of the range has effect of zooming in.

Translation of the horizontal range to the right will appear as if the model has been shifted to the left, which has effect of pan operation. The same is true for the vertical range.

To perform the above zoom / pan operations it is enough to modify only one range of the two. The second one will be updated automatically. See below for an explanation.

Note that ratio of lengths of the two ranges is constant and coincides with aspect ratio (width / height) of the component's window, otherwise the scene would look distorted. Because of that modification of one range results in automatic modification of the other range inside the DG Kernel component.

Aligning of 2D Views

Aligning allows horizontal or vertical alignment of two screen images or metafile drawings. If two controls or two metafile drawings are vertically aligned aligning windows (positioning at the same horizontal location on the screen and making width equal) of both controls or pictures guarantees that the drawing inside the window or picture will be aligned too, i.e. they will have the same amount of empty space on the left and the right side of the drawing and break lines, if present in both, will be aligned vertically.

Aligning two controls is not completely symmetric. The first control is the control to which the second control will be aligned to.

To align two controls or to align control to itself after a rotation of Frame of 2D View:

1. Query I2DView2_KC from I2DView_KC of both controls. Set SetupHorAlignment and/or SetupVertAlignment property of the first control to true.
2. Call I2DView2_KC.CreateTemplate of I2DView2_KC of the second control to create target configuration of the view as a view template
3. Call I2DView2_KC.SetupAlignment of I2DView2_KC of the first control to prepare the control for alignment
4. Call I2DView2_KC.CreateTemplate of I2DView2_KC of the first control prepare the control to store the configuration of the view in a view template.
5. Call I2DView2_KC.Align of I2DView2_KC of the second control to align the scene.

See also Cross View Sample