Like any artistic project, until you can see that final render, it's impossible to know how close you are to achieving your goal. As we will all know, from being 'almost finished' to being finished can sometimes involve 20 or 30 tweaks. This is fine when we're designing in Gimp or PaintShop, but Blender is a vastly different animal and tweaking your initial rendered project, even 10 times, can mean 20hrs of rendering (and that's with a small 5sec animation). You could be looking at a week of rendering time alone on larger projects that you need to tweak multiple times. With Blender and all the options it has it seem highly unlikely you'll get all the parameters perfect first time many effects will be trial and error). But trial and error seems impossible if you want to create furiously. I couldn't wait 2 or 3 hours between each tweak... I'd end up on a murder rap!

How do you girls and boys get around this problem. And it's not a matter of being careful and taking your time in the design phase. Even doing that... bveing as careful as you're able, it is just the creative way to look for improvements and want to speed this parameter up... scale that one down... change the effect... try another effect... try ten effects...


There are a number of ways to deal with this:

  • render a frame at low resolution and/or samples (i.e thumbnail). This should reduce render time but still give you are. This can effectively be done with the preview render in the 3d view.
  • learn more about optimising cycles settings (e.g. tile size, bounces, clamp)
  • render out to a multilayer EXR and use the compositor to perform final tweaks rather than re-rendering.
  • for animation, Opengl playblasts (the clapperboard icon in the 3d view) allow you a quick preview of how your animation will look, but without full materials and lighting. This can be very useful when normal playback is not at full
  • bake background props (inlcuding lighting etc) to textures once you are satisfied with them, that way you don't need to re-render them again (see http://www.creativeshrimp.com/light_baking_tutorial.html for a discussion of some of these techniques).
  • $\begingroup$ @user2257 feel free to accept one of the answers if it solves your problem, that said I think all the answers here are useful. $\endgroup$ – Sazerac Feb 20 '17 at 5:33
  • $\begingroup$ Yes, they are all useful. I'm not sure if members receive pts or anything for successfully answered questions, if so, once the answers dry up I'll pick what was most helpful and mark it as the answer. $\endgroup$ – Shane Levene Feb 20 '17 at 5:54
  • $\begingroup$ @ShaneLevene fair enough, you can also change your mind on acceptance, read meta.stackexchange.com/questions/5234/… for more info. $\endgroup$ – Sazerac Feb 20 '17 at 6:22

There are times when you need to render with all the samples, passes and whatever tricks you are doing in the compositor to get a real idea of what you are doing, but if you just need to evaluate a small part of the image you can draw a box on the image to determine what segment gets rendered.

In camera view press Ctrl + B and drag the mouse while holding the left mouse button

A red box will appear on the screen, and that will be the only area that gets rendered.

enter image description here

To clear the render border, press Ctrl + Alt + B. Or disable border rendering.

  • $\begingroup$ That'll be very useful rendering small parts of the work. I'll need to figure out how to do it with no mouse but am sure I'll manage. X $\endgroup$ – Shane Levene Feb 20 '17 at 5:52
  • In Addition to the Things the other People already said, you can got to the render Settings, there to light paths and try to reduce the Maximum bounces

  • You can also go to "sampling"(Where you set the amount of samples to render) and Change clamp direct and clamp indirect to something between 1 and 50, this reduces the noise but makes it less realistic(You loose a bit of lighting)

  • You can also bake the shadows and stuff like that to the object so that it is a texture, but you can only use it under certain conditions(e.g. when there aren´t moving objects)

  • $\begingroup$ Thanks Martin. 'Try to reduce the Max bounces'. Why try? May it not be possible? X $\endgroup$ – Shane Levene Feb 20 '17 at 5:50
  • $\begingroup$ @ShaneLevene max bounces can be important in certain lighting situations, sometimes those bounces will be necessary for good lighting, and other times you will be able to reduce them without impacting quality of the image. $\endgroup$ – Sazerac Feb 20 '17 at 6:20

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