Bug report #403

Rendering extremely slow with vector transparency

Added by Gary Sherman about 17 years ago. Updated over 14 years ago.

Assignee:Martin Dobias
Category:Map Canvas
Affected QGIS version: Regression?:No
Operating System:All Easy fix?:No
Pull Request or Patch supplied: Resolution:worksforme
Crashes QGIS or corrupts data: Copied to github as #:10462


Rendering with vector transparency set is intolerably slow if antialiasing is turned off. On a new install, we should set AA on by default.

If someone can confirm this, we should issue a warning when setting transparency if AA is off.


#1 Updated by Marco Hugentobler about 17 years ago


This does not happen on my system (Kubuntu 6.10, Qt-4.2.1). Performance is ok
for me with transparency and with/without AA.


#2 Updated by Gavin Macaulay - about 17 years ago

Works fine for me with Qt-4.2.1 under Linux with most polygons. With very complicated polygons or .shp files with large numbers of polygons I do see a small difference, but nothing that is significantly slower.

#3 Updated by Gary Sherman about 17 years ago

  • Resolution set to invalid
  • Status changed from Open to Closed

Perhaps this is an issue with my (and others) X11 configuration.

I'll close this issue.

#4 Updated by Markus Neteler over 16 years ago

  • Status changed from Closed to Feedback
  • Resolution deleted (invalid)

I am using Madriva2007 with QT4.2.1 and rendering is indeed extremely slow with vector transparency. Using SVN HEAD.

So I suggest to add a warning about this in case AA is disabled. I take liberty to reopen. In the German translation it is rather impossible to understand what checkboxes should be activated to avoid this slowliness.


#5 Updated by Tim Sutton over 16 years ago

Im testing with qt4.3 and I cant replicate. In many cases turning on anti-aliasing will actually slow down rendering so I think its going to be very confusing to put up a message saying 'turn on AA to speed up rendering with transparnecy, but AA will slow down rendering.'. Im going to forward this bug to 0.8.2, but I wonder if the preblem is resolved with qt4.3 in which case we should consider recommending this version of qt4.3.


#6 Updated by Tim Sutton about 15 years ago

  • Status changed from Feedback to Closed
  • Resolution set to worksforme

Closed - works for me under Qt 4.3 & Qt4.4. Please reopen if problem persists under a current version of Qt4. Suggestions to improve wording of options for clarity in German would be welcome.



#7 Updated by Anonymous over 14 years ago

Milestone Version 1.0.0 deleted

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