This must have been asked a million times but I can’t seem to find the right answer.
I’m a Blender noob and setting the number of samples a bit randomly, and was wondering what was the best procedure to define the optimal number of samples, especially for high resolution images. My last render was with very simple toon shaders and few objects, but took a whopping 35 hours at 150 samples (3 renderlayers), I must have done something wrong, I think, even if the result was 13500x13500px (i7 laptop 16GB RAM with medium graphics card so using CPU rendering).
So how do I go about it? Do I render a small part of the image at full resolution settings and inspect that? Do I make a low-resolution render (setting for instance at 20%) and hope that at high resolutions it will be fine? …?
Sorry for the probably stupid question, if anyone can just point me to the right thread or webpage I would already be grateful…
At a very first step make sure you haven’t accidentally checked “Square Samples”…
Other than that it’s hard to give advice without knowing anything about your scene or the render settings. And yes, finding the optimal number of samples is very much about test rendering, trial and error.
Check how much you have noise in your picture with some sample setting and how long it takes to render with those settings. Now think how long you can wait your render to happen? If it takes 1 day to render whole project without noise at all with like 2000 samples, you might take several hours away from the render time if you just allow little noise to it. Then you can procedural way to remove some noise from it.
OK, thank you, interesting!
About trial and error test rendering, especially concerning high-res images (like 10000x10000 and upwards), how to best go about it? Render the whole image at low res (like screen res) and inspect that, or rather render a small, difficult part in very high res (maybe like zoom in the camera)? Or doesn’t the second option make any sense?
Hi, result is similar with same samples on different resolution.
Render 20% of your goal resolution in 1/5 of render time.
The amount of noise depends on light situation and render settings.
If you try to render caustics with Cycles it will never finish, for example.
I’m in a similar boat, and tying up my computer for that long is asking for trouble – including crashes that aren’t the result of memory errors. One thing you can do is “break up” the image. There’s probably a way to “slice” and “stitch” it, but another way you can do it is to use CTRL-B to border select part of the image, and make sure that “Crop to border” is NOT selected. Save the result, then repeat with another section until you have all you want. Then, as long as you don’t move or change anything between renders, when you “stack” them, you should get a seamless render.
But with the large image size, long render times, particularly on CPU, comes with the territory. As long as you’re using mainly diffuse, 150 might be enough, but I often find that I like the results of 500 with a clamp of 1 for indirect and direct to minimize fireflies.