topic Re: Large File Size - cannot reduce in AutoCAD Forum

Large File Size - cannot reduce

Anonymous — Thu, 11 Feb 2016 15:12:03 GMT

Can someone advise on how I can reduce the size of the attached file? I am running AutoCAD LT 2015. Unfortunatley, since LT does not run LISP routines, I cannot use some of the tricks (i.e. hotfix) that I've used in the past to reduce file sizes.

Please advise.

Re: Large File Size - cannot reduce

rkmcswain — Thu, 11 Feb 2016 15:32:09 GMT

I don't really see any bloat issues (regapps, scales, dgn linetype data) in this DWG file.

If anything, you have a lot of simple geometry that could be made into blocks and then inserted into place instead of duplicating the same geometry over and over.

Re: Large File Size - cannot reduce

Anonymous — Thu, 11 Feb 2016 15:40:59 GMT

Thanks for your reply. I should have actually explained my issue a bit more. The file did not used to be nearly this large until recently, and I haven't changed the content of the file. I was using the file recently and received and error (unfortunatley I don't recall what error) and it created a temp file in that folder. My original file actually disappeared, but fortunately I was able to open the temp file and save as a .dwg. At that point, the file had grown in size by over 4 mb. It used to be under 2 mb.

Any idea what kind of error could have caused the disappearance of my file, and ultimatley the bloating of a temp file?

Thanks.

Re: Large File Size - cannot reduce

Anonymous — Thu, 11 Feb 2016 15:55:57 GMT

Correction, the previous version of the file was about 3.9 mb, so it was a little larger than I thought. I've attached for comparison. The content has probably changed slightly since this previous version, but not enough that it would warrant almost 3 mb more of file size.

Any thoughts?

I did try the process where I used the dxfout command, and then opened the dxf file that was created, audited, purged, etc and resaved as a dwg, which DID reduce the file size by about 2 mb, but also messed up all of my Layer States, so i wasn't able to use that file.

Please advise if there are any other methods of reduction of file size.

Thanks.

Re: Large File Size - cannot reduce

rkmcswain — Thu, 11 Feb 2016 16:41:42 GMT

One thing - the original drawing (6MB) contains a block (ceiling medallion) that contains 50000+ objects. Wblocking it out gives me a 1.4MB DWG. So that is part of it.

The 4MB drawing does not contain this block.

Re: Large File Size - cannot reduce

Anonymous — Thu, 11 Feb 2016 16:47:54 GMT

Okay thanks. I'll take a look into some of the blocks.

One last question - per your first comment, you mentioned that there are a lot of simple geometries that could be turned into blocks and inserted that way, as opposed to duplicating the geometries over and over. Does this substantially reduce the file size?

I'm trying to get a better understanding of how autocad reads geometries and how this converts into file size. If I have 50,000+ objects as simple geometries, and copy that group of geometries over several times, does that make my file considerably larger than if I created a block and copied the block over several times?

Thanks.

Re: Large File Size - cannot reduce

rkmcswain — Thu, 11 Feb 2016 17:19:20 GMT

I can't give you the savings in actual bytes, but consider this:

If you have 30000 lines, for each one of those, AutoCAD has to store two endpoints, the color, the layer, the thickness, etc. (Let's say there are 12 properties for a LINE) 30,000 X 12 = 360,000 bits of data (not literal bits in the computer terms, I just mean bit as some quantity)

If you copy that geometry 100 times, then you're at 3,600,000 bits of data that AutoCAD has to keep track of.

If you make a block out of those 30,000 lines, AutoCAD only has to store those properties one time. Then for every insertion of that block, AutoCAD only has to store the insertion point, color, layer, etc. of the block itself. (Let's say an INSERT entity has 12 properties too)

So by making those 30,000 entities into a block, AutoCAD has to remember the original 30,000 bits of data + 12 * the number of insertions.

12*100 = 1,200 + 30,000 = 31,200 bits of data as opposed to 3,600,000.

That is a very general assessment, because IDK what all AutoCAD does as far as internal data compression.

Okay, you made me test it...... (using AutoCAD 2016)

A DWG containing 3,600,000 separate lines is ± 81MB.

The same DWG with 30,000 of those lines made into a block and then the block inserted 100 times (so I still have 3,600,000 entities) is ± 930k (or about 1.1% of the size of the other one)

Re: Large File Size - cannot reduce

Anonymous — Thu, 11 Feb 2016 17:25:40 GMT

This is a great explanation, and exactly what I was trying to understand.

Thanks for your input! And thanks for testing it out!

Re: Large File Size - cannot reduce

rkmcswain — Thu, 11 Feb 2016 20:42:22 GMT

Oops. My math was off by a factor of 10.

360,000 X 100 = 36 million, not 3.6 million.

The point is still the same thankfully 🙂