Re: [Pythoncad-developer] Proposal geometry objects

[Yagnesh D. <yn...@gm...>]

We need to add the "Block" in the entity list.

On Fri, Feb 5, 2010 at 1:07 PM, Matteo Boscolo
<mat...@bo...> wrote:
>
>
> 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
>
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-- 
Best regards

Yagnesh Desai

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