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I have a 4k screen on my laptop which means that if I position a rendered viewport in one quarter I'm rendering on-the-fly a resolution of 1920X1080. My current solution to save time is make the viewport window smaller but then it's harder to see. What I'd really like to do is set a scale for the preview rendering of something like x0.5. In other words, whilst I size the rendered viewport to something like 1920x1080 I actually want Blender to only calculate 960x540.

Is there an option for this in Blender? Otherwise I'll end up down-sizing my resolution before starting Blender :(

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  • $\begingroup$ No, I don't think it is possible, as far as I know, If you are in camera view you can use border render around the whole camera frame then zoom out, so the rendered area is smaller, it is the only workaround I know. $\endgroup$ May 29, 2017 at 18:08
  • $\begingroup$ Alternatively change your default screen layout and add a smaller region exclusively for rendered preview that occupies a smaller portion of the screen. It is still smaller in actual visible size, but wont slow down your computer so much $\endgroup$ May 29, 2017 at 18:35
  • $\begingroup$ Assuming Cycles, reduce the number of Preview samples on the Sampling tab by a facfor of 4. Your preview will be 'spottier' (if that's a real word) bit the level of detail will be the same (ie, each 2x2 group of pixels at the higher resolution will contain the same samples as a single pixel at the lower resolution). $\endgroup$ May 30, 2017 at 5:54
  • $\begingroup$ Thanks for the input chaps. To be honest I think the best option is to lower the screen resolution whilst I'm working on the lighting. I'll try and find someway to suggest this as an improvement to blender! $\endgroup$
    – Phil
    Jun 3, 2017 at 17:29
  • $\begingroup$ Merged here, not sure to which branch or for which release though: developer.blender.org/… $\endgroup$ Sep 17, 2017 at 11:35

3 Answers 3

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there is a setting under performance that does that, it's called viewport resolution. 2x means half the resolution, 4x means a fourth etc.

Blender 2.8: enter image description here

Blender 2.7:

viewport resolution

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  • $\begingroup$ This is exactly what I was looking for and now embarrassed that I hadn't found it! Thank you :) $\endgroup$
    – Phil
    Apr 23, 2018 at 7:10
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    $\begingroup$ Anyone know where this is in 2.80? I can't find it anywhere :/ $\endgroup$
    – MrFlamey
    Mar 13, 2019 at 12:11
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    $\begingroup$ @MrFlamey i edited the answer for 2.8 $\endgroup$
    – J.Doe
    Oct 14, 2019 at 13:07
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If what you're after is getting a quicker preview, then just lower the number of samples for the preview renders (bottom red box in the picture).

Sampling settings

What I do is usually just lower it until I can't bear the quality any more; the lower the number the faster (and uglier) your preview render.

Cutting the number of samples in four will give you the same speedup as you would have gotten from halving the resolution. If you have Square Samples checked, then you should just halve the "Samples" / "Preview" number (which will in fact cut the number of samples in four).

Also, for the final render, don't forget to check out the new-in-2.79 denoising feature. In some scenes it enables you to cut the number of samples (and rendering time!) by a lot without any visible loss of quality.

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A general approach that will always work, even for eevee which does not have the options mentioned by other answers, is to use OBS.

PS: The eevee case is even more "special", as rendering performance on High-DPI screens isn't that big of an issue, however, if you are doing pixelated renders, it is very useful. This should also work in all OS-es, though I've only tried on Linux.

In short: create a viewport render in blender that is tiny and always in the same position. Use OBS to capture and upscale that image.

In detail:

  1. Download/Install OBS
  2. Set up a scene, and the video resolution you want to view the result in.
  3. Set up a screen grab source, this depends a bit which OS/WindowManager you are using. In Linux/X11 it is Windows Capture (xcomposite). Adjust cropping rectangle to match the small viewport output in Blender.
  4. Resize the input stream rectangle to fill your scene.
  5. (Optional) Right click the same rectangle, and change the "Scale Filtering" to for example point, for a "pixel perfect"-ish output.
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