Cycles:: Usability quirks, issues, bugs, and other concerns, discuss here.

The reason I’m starting this thread is to divert the continuous tidal wave of usability complains, concerns, and other issues pertaining to Cycles into its own thread so we can leave the development thread front and center on new development, new technique, and new optimizations.

The reason being that all of the noise being generated in the big thread is drowning out posts talking about new features as well as suggestions on improving them, so without further ado, feel free to discuss all of the other items here.

One person talked about how he is losing his work and doesn’t want the ESC key to have a global cancellation effect which stops the render even if the mouse is not in the image editor, so we can start with that.

Thank you Ace Dragon for giving me the opportunity to point out this topic.

I didn’t start to talk of the ESK key because I missed my work, it didn’t happen like that, I spoke about it just because it’s very possible that this occurs.
And for what? just because you have at hand an easy way to halt a rendering pressing ESC key.
But have we really need of that? Could not be a shortcut that is less prone to be hit by mistake, something like a three-keys shortcut, nobody have to use it so often to need it to be so handy.
On the other hand it can lead to loose hours of rendering, and you know, cycles renderings are not resumable.

Another person BTW, in that thread, told the same about baking phisical simulations, the issue is the same, you can loose hours of waiting. Very annoying.


i have never press ESC key by mistake ? how you can press it by mistake? Are you modeling while render? that you press tab or somethink? i really don’t know how to press ESC by mistake.

Same here, I have never ever had that problem. I find it pretty helpful to quickly be able to purposely hit ESC to cancel a render. I can’t really understand how you would accidentally hit the ESC key unless I was punching my keyboard out of frustration. If I ever did accidentally press it while rendering, I would be extra careful in the future to never do that again. I have a greater chance of accidentally tripping the power button on my power strip killing my computer, than I would accidentally hitting the ESC key while rendering.

I’ve actually done that a few times myself, but it’s usually because I’m working in another application on my second screen and use ESC to cancel a pop-up window or a text entry, and sometimes (especially now that I’m using my Wacom tablet so much) I accidentally clicked in Blender’s window and end up cancelling a CPU-based render instead. If it’s on GPU I don’t mind so much, takes a lot less time to catch up again.

It’s a fairly specific situation, of course, but depending on your workflow and setup, it can happen :yes:

It’s not really a matter of hitting it “by accident”…

Press “Esc” to close the file browser and the rendering will stop. Or start a animation playing with alt-A then press “esc” to stop it and the render will also stop even though your mouse is in the timeline window

This is a problem in the event system that the core devs are aware of and are working on a solution.

you hit the point, I usually continue to model while i render (and why not), and you know, the ESC is very often in hand when you model, so even if I’m aware of the risk, sometime happens to do it instinctively.

Thanks Harley for the information.


This is the recent thread on the mailing list.[email protected]/msg15143.html

I’m a profane, but would not be easier to change shortcuts for halting such processes, as I stated before, you don’t need to accomplish it every few seconds, also a three-keys shortcut, or Ctrl+ESC or such could work.


Changing question,
am I wrong that there’s not yet Camera Motion Blur in Cycles?
I have seen we have a soc-2013-cycles_mblur branch for Deformation MB, can I guess it will address also this feature?




yes, fortunately, you are wrong. :slight_smile:

camera motion blur was the first motion blur revision to cycles.

Thanks SterlingRoth, I’m happy about that,
but, can you, or others, give me some suggestions to make it works?
I’m able to render object MB but not Camera, both alone or together with object BM.

Thank you,


It should work just the same as object MB, just keyframe the camera moving and it should work.

It does not.

EDIT: I attached a test scene, I hope I’m doing something wrong, if anybody would try…
CameraMB-test.blend (146 KB)
Thank you

EDIT 2: I wanted to open the scene in official 2.67b and it works!
I was using the most recent r57376, so maybe there’s a bug.

Thank you


That’s very odd, it renders fine for me.

one thing that I was dissapointed to see not working is motionblur for changing focal length.

I want to do this!

Submitted bug report:35764

Thank you.

one thing that I was dissapointed to see not working is motionblur for changing focal length.

Have you tried to move the camera far/near and key it? Really I don’t know, I’m just trying.


that stuff is one click in photshop

yeah, but for animations, it’s a bit more convoluted. and for the sake of completeness, it would be nice to have it built into the camera motion blur.


@Kramon, if I wish, I could even hand paint it…