CODEWITHSUNDEEP
javaalgorithmdrawingdxf
baliman
baliman

Reputation: 620

DXF files INSERT entity

I am working on drawing dxf files in Java. So far I am able to draw, LINES, POLYLINES, TEXT, CIRCLE, ARC, LWPOLYLINES.

But I am having problems on drawing INSERT entities. I know this is mapped to block entities but when I draw them nothing get displayed. I understand you have to do some transformation on INSERT entities but I have no idea how to do that. I Googled a lot about this but no luck. So I hope you can give some direction how to process the INSERT entities. I also looked at some frameworks like ycad and dxf-code but that code is difficult to trace.

What is the algortihm for translation INSERT to entities like LINE and ARC

Thanks

Johan

Upvotes: 0

Views: 2448

Answers (2)

Lee Mac
Lee Mac

Reputation: 16015

The BLOCK entity (otherwise known as a Block Definition) is essentially the 'blueprints' for an INSERT (otherwise known as a Block Reference).

Rather than duplicating all of the geometric information constituting the block for every block reference in a drawing, the block definition (BLOCK entity) is a 'template' for each block reference, meaning that only the position, rotation & scale of each block reference need be stored.

The Block Definition resides within the Block Symbol Table and is comprised of a BLOCK header entity (defining the block name and origin (usually 0,0) among other properties), followed by all geometry forming the block definition, and finally a terminating ENDBLK entity.

All geometry contained within the Block Definition is defined relative to the origin of the Block Definition; then, when a Block Reference (INSERT) is created, the Block Definition geometry is transformed relative to the insertion point of the Block Reference.

Upvotes: 0

Andrew Truckle
Andrew Truckle

Reputation: 19107

It is hard to provide you a definitive answer because we see no code. But the way INSERT features are managed is described on the AutoDesk website. Here is the information for blocks in DXF files.

It also provides information about two important entries BLOCK and ENDBLCK.

Here is an example of a block that has a LINE and an ARC in it. The block will look like this:

Block

The block is called SAMPLE:

  0
BLOCK
  8
0
  2
SAMPLE
 70
     0
 10
0.0
 20
0.0
 30
0.0
  3
SAMPLE
  1

  0
ARC
  5
263
  8
0
 10
0.0
 20
22.4468613708478415
 30
0.0
 40
242.9028467109147016
 50
354.6976825438280798
 51
185.3023174561718918
  0
LINE
  5
264
  8
0
 10
-241.8634560136443099
 20
0.0000000000001137
 30
0.0
 11
241.8634560136443099
 21
-0.0000000000002274
 31
0.0
  0
ENDBLK
  5
262
  8
0

Basically, you have an entry which defines the block entities. It will have an origin and all the values are relative to the origin for the elements.

If you design it first then you will know what to do.

Once you have the BLOCK defined you will be able to use it as an INSERT.

The BLOCK itself. The key is the origin. Most are defined with a coordinate of 0,0,0. Then the ENTITIES are drawn relative to this origin for a scale of 1:1.

Imagine a rectangle that is 1 unit square for the scale factor of one. Then the coordinates would be:

-0.5,  0.5
 0.5,  0.5
 0.5, -0.5
-0.5, -0.5

I hope this information helps you.

Upvotes: 3

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