KernelCAD Documentation

Cannon sample is available in Enterprise level products only. The source code is located in Samples\Delphi folder of the installation directory.

Cannon is an advanced sample. It demonstrates calculation on intersections on a line with all objects in the model. It also demonstrates direct user drawing with IDraw interface, Runtime creation and manipulation of objects, programmatic manipulation of view with ILook interface and runtime programmatic positioning and arranging objects in the model.

See KernelCAD and Delphi for information about importing KernelCAD into Borland Developer Studio.

Running the Cannon Sample

By default the application loads Tank model. The user can load any .glm model. Location and Direction control groups allow positioning of the cannon anywhere in 3D space. Pressing "Fire" button executes calculation of all intersections of line of fire of the cannon with the model. "Objects hit" list boxes display all objects of the model, which have an intersection with the line.

Controls at the bottom of the page (hidden when there is no intersections) display information about the current intersection points for the currently selected object in the "Objects hit" list and normal of the surface at the point of intersection. This information is immediately updated when a different object is selected in the list or different point is selected as current in "Cur Intersection" up/down control.

The current intersection point and normal to the surface at the point are displayed in 3D with red and black lines.

The application works in two modes, determined by selection in "List intersection" radio buttons. In the first mode intersection points with all objects in the model are calculated and displayed. In the second model "Hit list" list box allows selection of which object in the model intersections are displayed for.

"Wire Frame" check box allows changing between surface and wire frame rendering mode.

Implementation

Calculation of intersections of each object in the model with the line of fire is done in OnFire procedure of the MainForm class. The calculation is performed with the help of IntersectObject procedure of ILineMetr interface. The result of the calculation is an IData interface, which gives access to array of records one per object intersection.

On start or load of a model InitModelInfo() procedure retrieves array of all objects in the model irrespectively to child/parent relationship via FlatObjectArray property of the model.

In addition to the loaded model the KernelCAD Control displays model of a cannon to visualize location an direction of the line of fire. The Cannon object is created dynamically at runtime in the CreateCannon procedure. The cannon consists of four sub-objects. Child objects are added to the cannon object with IArray queried from m_iCannon ISection interface. Cannon itself is added to the model with IArray queried from the model (array of top level objects).

Positioning of the Cannon is done in MoveCannon, the "Apply" button handler.

Line of fire and normal at the intersection point are visualized in OnClientDraw KernelCAD event handler. The event is activated with a call RequestClientDraw(true) in OnFire procedure. The drawing is performed directly using IDraw interface.