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I made a volumetric light based on a sphere, the borders are too notorious, it even looks like a texture. Is there any way to soften the borders like adding a blur, but in the single object, without messing with anything on the render layers?

blender showing the render and material nodes

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    $\begingroup$ I would add a gradient texture to reduce the density of the sphere volume the farther it gets from the center, and maybe scale the whole sphere up a bit. $\endgroup$ – gandalf3 Jun 12 '15 at 18:45
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Here I used a Gradient Texture node set to Quadratic sphere to generate the tapering of the volume. The ColorRamp node is used to control the strength, note the the right edge of the color ramp has a value of 1 (the center of the volume) and the left edge is 0 (no strength on the outer edges of the volume).
click for full size cycles material nodes

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You can do it in the compositor with a blur node on the light layer. Make sure to render in layers with one having the lights. Andrew Price has a lot of tut vids with this technique being used.

You might try adding fog.

Make sure you are not overdriving the lighting. This explains what I am talking about. Aliased edge around light source in cycles

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  • $\begingroup$ But doesnt this affect the other objects too? $\endgroup$ – beavoru May 28 '15 at 12:50
  • $\begingroup$ Which this? Fog might but layers will limit it to the things in that layer. $\endgroup$ – Douglas E Knapp May 30 '15 at 14:34
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You can use math nodes to reduce the density (or darken the color) of a volume material.

Here's a sample blend file: .blend file

Use ShiftZ in the 3D view to see the output.

material nodes

This was done with lots of math nodes to compute the falloff in volume density based on the distance from the object's center. I used an exponential function in X, Y, and Z, but another function or even a curve could be used. The output of the "density" node (on the far right) could be used to adjust a texture or some other volumetric effect.

The size of the cube holding the volumetric material and the XYZ "scale height" values are independent from one another. That way you can choose to scale the cube or adjust the scale heights, depending on your specific need in the scene.

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