Re: [Pythoncad-developer] Proposal geometry objects

[<ger...@gm...>]

Hi Matteo,


Step 1: The list of entities.
This are just remarks, maybe I see it wrong.


2) We can eliminate Segment, a segment is just a polyline with two points.
There must be a tool for the user to create it.

11) Is Polygon/Rectangle needed, this is a special form of a polyline.
There must be a tool for the user to create it.
Internal it is a (closed) polyline.

13) + 14) + 15) + 16) These are all the same.
A symbol itself is a entity.
A Marker, Arrow, section symbol and a Welding symbol are two instances of  
the same symbol entity.
We need symbol definitions that defines how the symbol looks like.
And we need symbol references that is a instance of the symbol definition.

18) Is layer an entity?
I thought it is more a entity attribute.
A layer itself has no visible representation.

19) Is Label not the same as text?
What is the difference?

20) What is a Ballon?

I think we should keep the list of entities as short as possible.
Each entity will cost us time to implement (object definition + drawing +  
printing).
We allway can provide different tools to the user.

Regards,
Gertwin



Op schreef Matteo Boscolo <mat...@bo...>:

> Hi Gertwing,



> I like your structure because we can store in a row of db a
> tuple that indicate the points and the kind of object that we are going to
> store.



> The db entity could be in case of point

> Id ++ coordinate ++ type

> 01 ++ (10,10)++ point

> 02 ++ (10,10,20,20)++Segment

> And so on for all the entity

> We can go on with this step:


> 1)
> Get a full list of the entity that we need do describe


> 2)
> Create a sort of classes that try to describe all this entity


> 3)
> Create the simple and efficient way to store in on db


> 4)
> Start to convert pythoncad entity to the new entity



> I would like to go on with this step before of all.

> So start listing all the entity that we will need in pythoncad




> 1)
> Point


> 2)
> Segment


> 3)
> Circle


> 4)
> Arc


> 5)
> Ellipse


> 6)
> Nurbs


> 7)
> Polyline


> 8)
> Hatch


> 9)
> Text


> 10)
> Image


> 11)
> Polygon (triangle/rectangle….)


> 12)
> Dimension


> 13)
> Arrow


> 14)
> Marker


> 15)
> Section symbol


> 16)
> Welding symbol


> 17)
> Groups


> 18)
> Layer


> 19)
> Label


> 20)
> Ballon


> 21)
> …



> Regards

> Matteo





> From:
> ger...@gm... [mailto:ger...@gm...]

> Sent: 04 February 2010 22:39

> To: pythoncad-developer

> Subject: [Pythoncad-developer] Proposal geometry objects






> Hi all,



> I did some thinking about the entity geometry.



> The current version maintains one point list where all entities make use  
> of.

> I want to preserve this method because it has some advantages.



> But I want to change the way the entities use these points.

> The current version defines different geometries for each entity (segment,
> polyline, arc, etc.).



> I want to define only two different geometry objects that all entities can
> share.

> It consist of only points, no start-, end angles, center points or radius.

> Because there are only points in the geometry transformations can be done
> really quick, all points are multiplied by the same matrix.



> If needed the program must calculate the center point, radius and angles  
> of
> circles and arcs.

> This is done far less often than entity drawing so this is more efficient.



> The main advantage is creating point lists for cairo drawing is more easy.

> All entities share the same geometry class, a single function is used to  
> draw them
> all.

> It is more easy to optimize a single draw function for speed than all  
> different
> functions for all entities.

> This excludes hatches of course which will have it own draw function.





> Some preliminary code:



> class Point(object):

> """

> Indicates a single point with x and y ordinates (2D point)

> The interpretation indicates how the connection is drawn to the next  
> point.

> With this construction linear and circular lines are constructed.



> These point objects are stored in a single table in the database.

> """

> def __init__(self):

> # id of point

> self.__id = 0

> # X ordinate

> self.__x = 0.0

> # Y ordinate

> self.__y = 0.0

> # interpretation connection to next point

> # L = linear

> # C = circular

> # None = not used (single point geometry)

> # more interpretation values needed for dimensions?

> self.__interpretation = 'L'





> class SGeometry(object):

> """

> Indicates a single geometry.

> This is used in segment, polyline, arc, circle.



> examples:

> 1) A segment geometry consists of a list of two points.

> The point interpretation from the first to the second point is 'L'  
> (linear)



> 2) An arc geometry consists of a list of three points.

> The first point is the start point of the arc, the second point is on the  
> arc
> and the third point is the end point.

> The point interpretation from the first to the second point is 'C'  
> (circular)

> The point interpretation from the second to the third point is 'C'  
> (circular)



> 3) An polyline consists of a list of three or more points.

> The point interpretation can be 'L' (linear) or 'C' (circular)

> This gives the opportunity to create polylines with linear and arc  
> segments.



> 4) An circle geometry consists of a list of five points.

> A circle is represented as two arcs where the first and fifth point are  
> the
> same.

> The point interpretation from the first to the second point is 'C'  
> (circular)

> The point interpretation from the second to the third point is 'C'  
> (circular)



> For a single geometry the geometry interpretation is None.

> Interpretation is used for complex geometries.

> """

> def __init__(self):

> # list of points ids

> self.__point_ids = []

> # interpretation used in complex geometry

> # O = outer ring

> # I = inner ring

> # None = not used.

> self.__interpretation = None





> class CGeometry(object):

> """

> Indicates a complex geometry.

> This is used in hatches.



> A hatch can contain islands.

> The list contains a outer ring and a inner ring (island).

> The rings are closed polylines (SGeometry objects).



> ??? Can inner rings contain other inner rings (nested islands) ???

> """

> def __init__(self):

> # list of single geometries.

> # order in the list is important, first a outer ring, than the inner rings

> self.__sgeometries = []





> Even a text can have the same geometry as a segment (two points).

> The first point is the text location, the second point is the rotation.

> The distance between the first and second point is the text height.





> Regards,

> Gertwin