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Frames

Frame is a system of coordinate axes. It is uniquely determined by 3D point of its origin in global coordinates and 3D vectors of its axes. To be valid, vectors of the axes must have length 1.0 and be perpendicular to each other.  Programmatically frames are manipulated by frame interfaces

Frame is very important and frequently used concept because it represents purified concept of location and orientation.

Nearly all items in 3D scene of KernelCAD have intrinsic frame member (property) called local frame, which defines location and orientation of the object (section). Geometry of a section is always defined relative to its local axes to make it invariant under any movement.

To create a new (standalone) frame call IDIObjGenerator.Create or IDIObjGenerator.Create2 with eType parameter set to eObjTypeFrame member of EObjectType enumeration. The returned IUnknown reference has actual type IFrame and can be safely cast to or queried from to convert to IFrame type.

Frames and Transforms

There is a close correspondence between farmes and transforms of 3D space. In particular this correspondence allows perfoming multiplication operation on frames similar to composition of transforms. See more details at Transforms topic

Drawing a frame

Local frame of a section is rendered if the visibility flag controlled by ISection.GetVisibleFlag() / ISection.SetVisible() is on.

A standalone frame can be added to the scene with the help of Frame Graphic Item, which is a software object implementing IGraphicItem. To draw a frame:

• Create new Graphic Item by calling DIObjGenerator.Create( EObjectType.eObjTypeGraphicItem ) and casting (queering) the return to IGraphicItem type
• Query IKCContext from the IGraphicItem
• Call IKCContext.SetParam(0, iFrame) where iFrame is IFrame implemented by the frame to attach the frame to the graphic item.
• Call IKCContext.SetDoubleParam(0, size), where size is length of axes to be drawn. Use IMetrics.GetDimensions to obtain size of the model programmatically.
• Obtain IView of the KernelCAD component with GetView
• Call IGraphicItem.AttachView to attach the view
• Call IGraphicItem.Draw inside handler for ClientDraw KernelCAD control event to draw the frame. Make sure that RequestClientDraw is called on start of the application.

See CreateFrameGraphicItem() method of Collision Path sample for an example.

A permanent object, which represents a frame and can be saved with the model can be modeled in 3D Debugger or created programmatically using Line Strips