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The Cycles F.A.Q


Ever since Brecht announced his work on a new GPU-powered renderer Cycles, it's been the biggest buzz in the Blender community that I've seen in a long while. If you need to catch up, check out this useful FAQ by DingTo.

DingTo writes:

It’s amazing to see the great images people are already producing with it, keeping in mind that the Engine is still in “Alpha” stage. So, it’s not feature complete yet and speed will be improved as well in the future. Based on own knowledge and infos Brecht and Ton put online, here are some answers to common questions I stumbled upon while reading various Cycles discussions


About the Author

Avatar image for Bart Veldhuizen
Bart Veldhuizen

I have a LONG history with Blender - I wrote some of the earliest Blender tutorials, worked for Not a Number and helped run the crowdfunding campaign that open sourced Blender (the first one on the internet!). I founded BlenderNation in 2006 and have been editing it every single day since then ;-) I also run the Blender Artists forum and I'm Head of Community at Sketchfab.


  1. Nice to see a bit more info on Cycles without wading through that mammoth Blenderartists thread!

    That said, I find that the biggest question/assumption is about the biased/unbiased nature of the renderer. Brecht talks (on the Blender wiki) about a physically based but not physically correct enginer. I assume that it is to fill the gap between the current BI approach and the likes of LuxRender.

    Any chance of a bit of commentary on that?

  2. @Juspoted
    The whole point of Cycles is to create a better, future proof renderer for Blender and to completely replace BI when it's finished.
    It's not going to be and is not a completely physically correct renderer. Well, doesn't seem like you will be able to make rainbows out of light beams :P

    You will be able to do anything BI can though....

  3. I think that cycle is too early to call it a official replacement for blender render.
    There other render engine that are in development that could obsolete Cycle render
    and I rather have the choices to use what render I'm comfortable with including Cycle.
    Please don't throw always the classic.

  4. @blender pro
    Did you even read the article?
    "It’s amazing to see the great images people are already producing with it, keeping in mind that the Engine is still in “Alpha” stage. So, it’s not feature complete yet and speed will be improved as well in the future."

    There is still a long road to go before Cycles become the main renderer. :)

  5. Well, it sounds great. I just hope "replacing Blender Internal" will NOT mean I won't be able to render a quick (even if physically inaccurate) scene, but will have to wait for an hour for (nearly) all the noise to disappear...

  6. Artorp,I did and as I say by the time Cycle come out of beta other render engines will be more advance then Cycle.Hardware and graphic card are getting more up to speed that Cycle will be incompatible,cause is a open sources property not commercial. Seeing is believing-Watch!

  7. @blenderpro
    Not sure why you'd say Cycles will be incompatible, when GPUs get faster so will Cycles number crushing. And of course there will always be other better renderers, but few are open-source and/or utilize GPUs.

    @The Entire Blender Community (please answer)
    I've asked this before and I have not seen an answer: how do you render animations with an unbiased renderer? I don't understand how it knows when to stop rendering a frame and move on to the next one. If there is a max. threshold that you could set, then won't you have inconsistencies between frames. Any input "knowledgeable" folks can provide would be much appreciated.

  8. Hmmm, the comments somewhat reflect my first one. It would be nice for the FAQs to have a clearer explanation of the biggest question that floats about, which is the unbiased/biased one.

    My understanding is that an unbiased renderer is one thing and does, indeed, take a very long time to produce a grain-free image. From that starting point there are levels of bias depending on how many simplifications and tricks are used to speed the rendering process up. Even LuxRender, which most see as a purely unbiased engine, allows you to introduce elements of bias in order to speed things up. From the other side, Yafaray might be good at spitting out a relatively quick, biased, image but if you push it towards the more accurate (less biased) end, then you can still wait hours to get a clean image. The whole thing is a balance.

    What is obvious to me, but seems to be raised a lot by others, is whether Cycles will replace BI and force us to wait hours for an unbiased render to clear up. Obviously that is not the plan and, indeed, Brecht makes it pretty clear that an engine suitable for animation is a priority for him. Nobody is going to replace BI with something inferior, obviously. I expect that the two will run in tandem for a while (and it could be quite a while), as we all get used to Cycles and it picks up the capabilities of BI. One of those capabilities will undoubtedly be control over the level of bias, so you can spit out a quick, clean render when you need to.

    I hope I've got that about right! Exciting times, that's for sure.

  9. @BlenderBoy
    As a couple have said before me, you can set the max number of passes it will do before saving the image.

    I'm not sure how Cycles will be set up, but in Maxwell, you can continue rendering a frame from where it left off. This can be a huge advantage.

    Imagine rendering out your movie really quickly, just to see how the light works. It will be very noisy. But when you find your sweet spot with the lighting, you can just keep working on the frames you already have done. I don't know if I explained it good enough, but it can save you a lot of time when doing animations!

  10. wel i don't know if its a real path tracer
    it renders caustics so it must calculate light beams too so it renders 2 diffrent beams from the light and from the camera
    i have got the problem that the image noise crears up vary rapid and after there is no noise i have to wait almost 5 times the get the caustics clear
    i hope brecht implements some feature that balances the camera and light beams so rendering power is more efficient used.

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