The transform module with its automation is a revelation to me … the tools in Lightroom and ON1 are now where near as good at this little module.
I have been re-editing some older images where perspective was an issue, and I have used the automation buttons in the module and I am blow away at the accuracy of this.
Far better than I could achieve manually in such a short time.
And that is now a somewhat old module 
As said many many time please do read the documentation, you do not know what else you are missing!
What s the transform module ? Do you mean perpective correction ?
Marco … you are correct… my mistake… it is the perspective correction module.
I stand corrected.
Perspective correction in Darktable is unfortunately pretty inferior to Lightroom 
How so?
auto perspective alignment seems to give better results in Lightroom. More realistic results, while Darktable often times completely warps “the space and time” of the image. In those situations one would like to manually add perspective lines like you can in Lightroom but in DT you can only enable or disable the lines created by the algo which is a lot more work than just manually adding 3 lines and you can never achieve the result you want, only what the algo gives you.
And while you are enabling or disabling those lines with a brush like tool, keep in mind you cannot change its size so you’ll be brushing a lot since the default brush size is pretty small, or you’ll brush over lines you wouldn’t want to since the brush size still isn’t so tiny tiny when you need to brush over the line that sits in the middle of a few other close ones.
You could achieve anything with sliders but let’s face it, you’ll never get the perfect result however much you tinker with them.
Thanks for the info. I never played with the Lightroom perspective module before, but being able to manually add the correction lines does sound like it could be a useful feature.
You can manually draw correction lines in the crop and rotate module. Both vertical and horizontal transforms are supported.
Have you tried the keystone tool in the crop and rotate module? It’s similar to Lightroom’s guides feature.
I am running version 3.2.1. Where do I find this Transform Module?
Caruso
@carusoswi: People in this thread are referring to the “perspecitve correction” module (in the “correction” group) for the automated perspective correction. For manual correction, @bastibe and @europlatus mentioned the “crop and rotate” module (in the “basic” group). You can find both by doing a search (or in your “favorites” group, if you favorite both of them in the ☰ menu for each module).
Be sure to read the “keystone” section of the “crop and rotate” module docs to learn how to manually adjust the perspective!
Additionally, the “perspective correction” module’s docs has some good info too.
Really, all the docs for darktable are great! It’s worth spending some time there. They’re organized so that looking things up quickly works well too. Sadly, they’re out of date on the official site (stuck at version 2.4), but most of the modules are similar enough.
Thankfully, a preview of the 3.0 docs are at “darktable 3.4” in the darktable usermanual and there’s an effort underway to bring the up to darktable 3.4 @ documentation · GitHub
I’ve read that there’s a goal to have up-to-date docs finished for the 3.4 release, which is scheduled for Christmas — just 69 days away from today!
Yes, that’s my goal 
And many people have helped to reach it. At this stage I cannot say we will have a fully up-to-date doc for 3.4 but the current state is very close.
Great stuff. By the way, I’m an editor by profession so if you need some help with reviewing text in English, I’m happy to contribute. My workload is such that I probably won’t be able to write much, but for proofreading and editing, I could help.
omg omg omg!!! Yes! Yes! Yes! That’s it! Oh wow, I can’t believe I didn’t know about that feature 
Although I can already see a few issues with how this feature is designed in Darktable it’s still incredible and with potential to be better than Lightroom’s guided perspective correction 
How many times we said : Read The Doc !
I’m not sure this applies at this situation as the feature has literally nothing to do with crop and rotate and one would expect to find it in the Perspective correction module. I wouldn’t be able to find it even if I was looking for it.
Anyway, let me enjoy my happiness a bit 
What he means is puruse the docs in general, like browsing through a catalog, in order to get to know that the modules can do. No telling what other little easter eggs you may find 