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Varkon Interactive users manual

# Modeling concepts

## Positions

In Varkon, a position is any specific place in the universe that can be defined using MBS language. One way is by it's coordinates, (x,y,z). Another way is by saying "the end of that line" or "the centre of that circle". The most usual ways to define positions are easily available as buttons in the lower part of the menu window but there is actually no limit to the number of ways you can define positions if you know the MBS syntax. When so, use the mbs button.

See the VECTOR datatype for more information about positions.

Note that in Varkon, a position is not a point ! Points are geometric entities with graphical attributes that can be displayed in graphics windows. A point of course also has a position.

## Entities

There are 17 entity types in Varkon. See the entities section of the Varkon Interatcive users manual for a complete list. Each entity can be created using one or more specific methods. Many of these methods are available through the create menu (and sub menus) but with MBS you can create entities in almost any way you can come to think of. Most of the Varkon entities also exist in a similar form in other CAD systems. Some systems call them objects instead of entities.

## Coordinate systems

Varkon uses the concept of "the currently active coordinate system". The BASIC coordinate system is the system that is active when you start a new job. You can create any number of LOCAL coordinate systems and you can activate each one of them individually at any time by pressing the CSY button in the menu window. Varkon uses the currently active coordinate system as the reference when you enter coordinates, directions or angles from the keyboard. Varkon also uses the XY-plane of the currently active coordinate system as the "current work plane" for operations that need a plane to be defined.

See Coordinate systems for more information about coordinate systems.

## Sense of direction

In Varkon, wireframe entities (lines, arcs and curves) have two ends. One is the start, and the other is the end. Which is which depends on how you create the entity. The sense of direction is always from the start to the end. If you create a line for example, with two positions, the first position will be the start of the line and the second will be the end. You can access any position on a wireframe entity through the on button in the lower part of the menu window. You will then have to enter a parameter value. A value of zero is equal to the position where the entity starts. A value equal to 1 (or more for curves with many segments) is equal to the end of the entity. Values in between represent positions along the entity. A value of 0.3 for example, would be a position 30% along the lenght of the entity in it's sense of direction.

Surface entities have 2 senses of direction, U and V. Similar to wireframe entities these are controlled by how you create the surface. You can access any position on a surface by supplying 2 parameter values, one for U and one for V.

## Identity and reference

When you create an entity, Varkon automatically assigns a unique identity (ID) to it. ID's are integer values preceeded by a "#". If you start a new job and create an entity it will get an ID equal to #1. Next entity will become #2 and so on. As a beginner, using Varkon in explicit mode you don't need to know about ID's but if you want to use Varkon in generic mode and learn MBS, ID's will become very important.

Once an entity is created you can use it's ID to refer to it. The end position for example, of a line with ID #5 is end(#5) in MBS notation. When you use the ID of an entity to access the entiy in some way this entity is referenced. An entity which is referenced may not be deleted and if it is changed, the referent needs to be updated as well. This is done automatically by Varkon in generic mode.

See the REF datatype for more information about ID's and reference.

## The part concept

A part is an entity that is often used to represent real world parts. In Varkon, parts are created by calling and executing modules. Since a module is in fact a computer program you can feed a module with different input each time you call it and the module can perform calculations and make decisions automatically. This means that parts can be parametric and intelligent. A part may consist of any number of entities including other parts.

You can only create modules in generic mode but you can use them to create parts in explicit mode as well. A module is the generic version of a part and the part itself is the explicit version. See: MBO- and RES-files, what's the difference ? for more iformation about generic and explicit.

## Graphical attributes

All entities have graphical attributes that can be used to control their visual appearence. Some are common to all entities and some are unique. All entities for example, have PEN and a LEVEL number. Points also have PFONT and PSIZE while lines have LFONT and LDASHL, and so on. For a complete list of all graphical attributes see the set() procedure.

When you create an entity, it automatically inherits the currently active graphical attributes that apply to it. To set the currently active attributes, use menu/settings/attributes. You can also edit an attribute of an individual entitiy once it is created with menu/edit/attributes.

Varkon version 1.19C svn# 120