Cycles Render – parameter changes have no effect

I try to render in cycles the most basic scene: A cube, a plane, a sun and a camera. No textures, no materials, no additional layers, no nothing. 128 samples take 46 seconds.

I tried to change +/- all parameters described in Youtube etc. to increase render-speed and nothing changed (45.6 to 47 secs for 128 samples). I render on CPU since I have no GPU. I changed:
-Tile size
-Sun max bounces
-Render dimensions border active
Within Blender 2.78a, the only parameter to speed up is Branched Path Tracing; set to 4 AA samples, rendering takes 2 secs, but the result is BAD.
In Blender 2.79 the same scene takes 37 instead of 46 secs.
Is it normal that changing parameters does not affect render time?
Many thanks upfront to all of you smart guys!

What’s you machine spec? where’s the blend file for us to try out so we can see ALL your setup?

Same setup, standard Cycles settings, on my Mac (Intel i7 - 16Gb Ram) CPU render takes 4 seconds, on my server (MSI GTX980 4Gb GPU) GPU render takes 1.2 seconds. Both with “Denoising” active and “Filmic” colour management (Blender 2.79).

More info please!

Cheers, Clock.

best would be for you to share a scene file, since with it anyone can observe what’s been done (wrong or correct) :wink:

These are my machine specs:
Intel i5-4200 CPU @ 1.6GHz 2.3GHz, 8Gb RAM, Windows 8.1, x64. When I add denoising the render time goes up to 1 minute in Blender 2.79!

This is the file I am working on:
So many thanks upfront!

Yes, if there is nothing in your scene that corresponds to those parameters. For example: You just have diffuse shaders in your scene. So, if there is nothing that produces caustics, why should switching off refractive or reflective caustics have any effect on the render time?

So, it is normal that a simple scene like mine needs 40 secs for rendering with an Intel i5 CPU?

That scene took my i7 2700k @ 4.6ghz 12.59 seconds. 40 seconds or so seems about right for your cpu specs. You use the denoiser in conjunction with fewer samples to get similar results faster.

Denoising slows rendering more down than it helps (at least in my setup). Many thanks for all of your help!

How can I label this thread as solved?

Edit first post, click go advanced button, elect prefix “solved”

i agree your your file has no nasties in it. You either need a new CPU, or if it’s a tower system think about getting a GTX979 or 980 they are a good price as later ones also exist.

Cheers, Clock.