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KernelCAD 3D Debugger

KernelCAD 3D Debugger (3DBugger) is a useful tool for 3D development. It can be used for any kind of development, not necessarily development with KernelCAD.

3DBugger window is a special mode of Modeling Studio. 3DBugger works concurrently in collaboration with KernelCAD component, loaded on by the application, which is being debugged (debugee application or simply application). In this situation KernelCAD component is called Client Debugger Component

3DBugger allows display and analysis of intermediate steps and state of the application while the application is being debugged by stepping through in a conventional debugger like Microsoft Visual Studio.

This is similar to Console.WriteLine() in .NET, printf in C, TRACE in MFC, etc with exception that the output window is three-dimensional and instead of text lines there are 3D objects.

See also 3DBugger Sample

Quick Start

To debug an application query I3DBugger from IDIObjGenerator and call I3DBugger.DumpObject with representation parameter set to ISection  of the object to be displayed or to IModel. to display a model.

Use also IDraw, and IDrawUtil, queried form I3DBugger to add simple primitives or standard parametric objects to the debugger display.

To start debugging Start Modeling Studio from the computer's Start menu. Select Debug > Start in the menu. Step through your code and watch how I3DBugger.DumpObject and other 3DBugger calls display the progress in 3D.

It is strongly recommended to keep the Model Explorer open as it shows sequence of added objects, other useful information and provides shortcuts for the most frequent operations.


3D Stream

Debugging stream should be thought of as a virtual model file, which is displayed in the 3D output debugger window. On I3DBugger.DumpObject or I3DBugger.Dump the object is written into the stream from the debugee application. 3DBugger application is notified about the stream change and adds the last dumped objects to the scene.

If the object has the same hash supplied in I3DBugger.DumpObject call or via debugging context as an existing object the object is updated with the dumped version. Visibility and some other properties set from 3Dbugger remain unchanged.

An application can dump into several streams. This is useful, for example, in situation when some of calculations are two dimensional and should be isolated from 3D objects. Several applications can dump into the same stream simultaneously. 3D debugger can display a single stream only, but several instances of debugger can run simultaneously.

Streams are distinguished by its names. If an application uses only one stream there is no need to worry about streams as a default stream named "Dump" is used

To open and/or activate a stream for dumping from a debugee call I3DBugger.AttachStream. To attach 3DBugger to a non-default stream select Debug > Options in Modeling Studio menu.

Only one stream can be active at a time in an application. When there are several streams I3DBugger.AttachStream is used to switch between the streams.


The dumped objects do not have to be the exact geometric object of the debugee application. Quite often it is useful to simplify the object to show only its location and orientation and may be some key features of its shape. This simplified version of the object is called representation.

Normally any geometry aware class would have a Dump() method, which knows about structure of the object and can either construct representation dynamically, dump an existing KernelCAD object or use IDraw, and IDrawUtil interfaces. See Plane and Segment classes of 3DBugger Sample for an example.

Output Management

It is recommended to add meaningful names to the dumped object. It can be done either by modifying name of the representation with ISection.SetName or use Name property of the debugger state (see below) in case of IDraw or IDrawUtil.

It is also recommended to set valid hash parameter while using I3DBugger.DumpObject. The pointer of the original object in C++ is  a good candidate for hash value. Use Object.GetHashCode Method in  .NET.

Some objects are very volatile and should be displayed for short time only. For this purpose a dumped representation can be marked as Transient Object by setting the relevant parameter of I3DBugger.DumpObject. Transient objects are removed from the debugging 3D stream during the next call to I3DBugger.BeginDump. Objects can also be marked as transient by using Hash property of the Debugger state (see below).

The 3D Debug stream can be cleared with I3DBugger.BeginSession, which also resets all parameters of the debugger state. Relatively complex programs can make several calls to I3DBugger.BeginSession when  executions passes from one major part of the algorithm to another. To clear the stream from 3DBugger application use Action > "Delete All Objects" menu option of Model Explorer. Be aware that the change is saved without warning.

Indirect Dump

The Client Debugger Component implements IDraw and IDrawUtil, which can be used to dump some primitives indirectly, i.e. bypassing I3DBugger.DumpObject. Using IDraw and IDrawUtil is identical to their use inside the ClientDraw event. The difference is that the rendering is persistent. The result is an object in 3D debug stream instead of image on the screen.

Dump of a primitive happens on call to End or on call to any method of IDrawUtil. For performance the object is not displayed immediately assuming that there can be some more objects added to the stream before flashing it to the debugger window. Call I3DBugger.Dump to force the 3DBugger update.

Use 3D Debugger State (below) for setting name, hash and other properties of the object, which is about to be dumped.

State of 3D Debugger

Properties of dumped object like name and transient property for indirectly dumped objects can be set using 3D Debugger State. 3D Debugger State is a collection of several parameters, which are used when the next indirect dump occurs.

Property Description Type Interface call Default When reset
Name Name of the dumped object String SetStringParam(0, val) Empty string After dump of any object
Transient Dump as transient object Boolean SetBoolParam(0, val) False I3DBugger.BeginDump, I3DBugger.BeginSession
Hash Identifies the dumped object for 3DBugger Integer SetIntParam(0, val) 0 After dump of any object
CreaseAngle Triangles or quads dumped with IDraw are assumed to form a sharp edge if angle between the faces is less than that value Double SetDoubleParam(0, val) 30 degrees I3DBugger.BeginSession

To access the state use IKCContext queried from I3DBugger.

Use IKCStack to save and restore the state.

See also 3DBugger Sample