QCAD.org Forum

Hi,
I quite often run into this problem when I open "complex" files coming from Autocad, such as the one attached.
QCAD eventually opens it, but it becomes unbearably slow. It gets far too slow, even to start deleting layers.
(purging unused layers and blocks does not help much)

My first impression is that it happens when the original file contains viewports.

What would be a workaround for this problem?

Any help will be very much appreciated

Version: 3.32.4.0 (3.32.4)
Build Date: Sep 4 2025
Operating system: Windows 11 Pro

Hi,

This topic comes up all too regularly.
Perhaps you can search the QCAD forum on terms like: 'Slow', 'Complex', 'Autocad' or 'ACAD', 'lag' or 'lagging'.

Would be enlightening after you tested the free trial version.
Very similar to a test drive with a 'discounted' car, where some unpleasant facts come to light.

"QCAD is never intended to be yet another ACAD clone."
"When comparing QCAD to other CAD systems, please consider the platform availability and license cost as well for a fair assessment."

If asked or complained over then Andrew, the QCAD developer, might consider a full refund.


Viewports are typically included on Layouts.
On open QCAD (attempts to) render Model_Space what is not a Layout Block.
They should not matter in the rendering process of Model_Space.

Your example file loads slow but rendering and navigation (Re-rendering) is problematic.

From what I see until my version of QCAD fails ... The content that matters can be created far less complex.
Sometimes one has the tendency to over-complicate things ... Simply because it can.
Re-editing by numerous parties may include numerous different styles and methods based on personal habits.

QCAD zooms automatically far out because there is content in Blocks with origins nowhere near the content.
A proper Block origin would not place these artifacts far from the intended position.
Probably the (last) source application(s) does not strictly follows the DXF rules ... Even when they written them.
That might even be on purpose.

An nearly 8Mb binary DWG file might be a large an complex drawing.
This example fails where other similar sized files are also rather slow but don't fail at all.
I would already increase the Auto-save interval or disable that because this file is always a very much larger DXF being textual.

I once compiled a list with things that might slow down QCAD in reply to: Suggestion for making QCAD "feel" faster.
For users that create very complex 2D drawings with QCAD.

Is there an 'out of the box' fix for working with massive DWG files, to make QCAD comply? NO.
But there is a fix for the simplest 2D content of such files: PEBCAK.

Regards,
CVH

Thanks for the detailed explanation. I was about to ask a similar question about slow performance with complex DWG files, so your reply really helped me understand the situation better.