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I have a simple scene. Added an icosphere and emission to it. Set the volume scatter nodes. I can't find the rays coming out. Just at the fog and there's no clear light coming out. What setting am I missing?

Simple scene enter image description here

No Gods Rays

enter image description here

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Because your light source is too big.

God rays are just interesting/complicated shadow patterns hanging in space. If your light is throwing soft, boring shadows, the god rays of those shadows hanging in the air area going to be blurred and boring too.

Just as a start, here's your scene with the Icosphere mesh light at 1/20th the size, and 100x the power:

Render of scene with the Icosphere mesh light at 1/20th the size, and 100x the power

Since we just need a small sphere light for this, we'll replace that mesh with a point light as it's a bit more efficient and easier to control. I've set this one to size=0.02 (2cm) and the power to 1000. I also got rid of the volume cube around the object, unless you want some 2-tier rays, you don't need that AND the world volume.

Looks like this render result of previous paragraph

You can vary the sharpness of the shadows by adjusting the lamp size. That will sharpen the rays as well. Here's the point light at 5mm instead of 2cm

Render with the point light at 5mm

Or tweak the lamp colors. Here's 2cm point lamp with an orange color. I also switched to branched path tracing, as it tends to be good with "volume show" scenes like this since you can turn up volume sampling. Plus I flipped on the denoiser:

pretty render with settings in the previous paragraph

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    $\begingroup$ Thats really looking awesome. Can u plz share the last file $\endgroup$
    – atek
    Jun 15, 2018 at 5:04
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    $\begingroup$ I neglected to hit "save" while I was working through it. :\ $\endgroup$
    – JtheNinja
    Jun 16, 2018 at 1:00
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    $\begingroup$ same problem here with this question i tried all but did not can plz go through the file blender.stackexchange.com/questions/111409/… $\endgroup$
    – atek
    Jun 24, 2018 at 4:18

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