RubberbandEngine

(Still in development)

The RubberbandEngine is designed to take over the computation of the required points to display a rubberband in a CAD application.

The engine is designed to work with primitive types to compute the rubberband such as:

• Lines between two Points
• Circles around a midpoint with a given radius and orientation
• more options coming.

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Setup engine from JSON

The engine can be set by means of a json object.

All members and fixed values used in the json document are defined in the file <rbeCore/jsonMember.h>

The json object that is used to setup the engine must contain the following members:

• RubberBandSteps: (Array) Contains all steps for the current Rubberband

JSON: Step

The step must be an object having the following member:

• Step: (Integer) The ID of the step. The IDs MUST start at 1 and count up
• MayEndWithout: (Boolean) If true, then the creation of the rubberband may end on the step before the current one
• Projection: (String) The axis on which this step will project (May use: UV or W)
• Limits: (Array) Contains the limits for the axis for this step
• Points: (Array) Contains all the points created and computed at this step
• Connections: (Array) Contains all the connections that are created at this step

JSON: Point

The point must be an object having the following member:

• ID: (Integer) The id by which the point can be referenced (The ID must be unique)
• U: (String) A formula to describe the U value of this point (See: Point-Formula)
• V: (String) As "U" but for the V axis.
• W: (String) As "W" but for the W axis.

Point-Formula

A formula to describe the value of one of the Points axis may contain:

• Regular expressions as +, -, *, /
• The distance operator '>' that will determine the distance between two referenced points
• A reference to another point, prefix '$' + the id of the Point *
• A reference to the origin point 'Origin' *
• A reference to the current position 'Current' *

Expressions: '>' > '*' > '/' > '-' > '+'

Example: A formula for the U axis at a point, the position will be calculated with the following formula: Origin.U>Current.U+$1.U In words: The distance on the U axis between the Origin point and to that result will be added the U value of the Point with the ID 1

• All the referenced points must provide the axis of which the values will be retreived (U, V, W)

STEP

Steps describe the sequence in which the rubberband is created. Upon creation of the Engine the invisible step 0 is activated. When switching to the next step, all Points contained in the current (the old current) step will updated their values and make them read-only.

A Point in a step may not reference a Point of the same step. Points from one step may not reference points from a 'later' step.