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Hi I am creating a Doctor who Sonic screwdriver model in Blender and am having difficulties creating the material for the blue light on the end. Preferably I'd like one material which emits light and one which doesn't.

Reference pic for without light: Doctor Who Sonic Screwdriver Reference Photo

Honestly I don't really like the pics on Google of it emitting light Here's a video in which you can see it with the light on https://www.youtube.com/watch?v=KgSgplNgpmw#t=58

Any help is much appreciated!

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I would use two objects (or separated parts of the same object), the emitting object being separate from the cover.

As far as the materials go, it depends on how much you want to fake it to increase render times/decrease noise.

Realistic

A realistic setup is probably the simplest, with just a simple emission shader for the emission object and a glass shader for the cover.

I've used clipping border (⎇ AltB) to give you a cut away view of the objects:

enter image description here

The main thing to note is that the cover is not solid, it is hollow (this can be done with a quick solidify modifier). The reason this is important as it has a large impact on the way light is refracted through the cover.

With some simple compositing to simulate the way a camera will behave when exposed to a bright light source (bloom), a nice glow can be achieved:

enter image description here

The downside to this is that it will produce a lot of noise. This image was rendered with 1000 samples, but as you can see it still needs some more:

enter image description here

Fast/less noisy

This is more complicated, but should help rendertimes by reducing the amount of noise at the cost of physical accuracy.

There are probably several ways to optimize such a setup, but here's one of them:

The main point here is that a point lamp is used to do the actual illumination instead of the emission mesh.

The point lamp is also not refracted, it's light is allowed straight through the cover, but absorbed where the cover mesh is thicker (kind of faking those nice caustics from the "realistic" example)

To make sure the volumetrics don't cause too much of a slowdown, make sure volume sampling is set to Equiangular and that Homogeneous is enabled on the cover material:

enter image description here

Rendered in 200 samples:

enter image description here

As you can see, there is still a little noise, mostly caused by the mesh light which is emitting light that gets refracted/reflected by the cover. I couldn't immediately think of a solution which would make the mesh light only illuminate the inside of the cover, and not refract outwards.

The only reason the mesh light isn't making as much noise as in the "realistic" render is that it is dimmer than in the realistic version. This isn't very noticeable though, since the lamp provides plenty of light.

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  • $\begingroup$ I think I'll have to go with the less realistic as I'm using hdri lighting which seams to increase my render times significantly. How did you create your lens? looks much better than my simple half sphere. This is my first project in blender, by the way, so I'm really new to all this... thanks so much for the help with everything! $\endgroup$ – Kittenmittons Oct 11 '14 at 5:19
  • $\begingroup$ @Kittenmittons I just extruded random face loops until it looked detailed.. I'll upload the .blends for you to play with :) $\endgroup$ – gandalf3 Oct 11 '14 at 6:29
  • $\begingroup$ hehe, it's ok I managed to get something similar :) My display seems to be a bit different...I don't have the equiangular and homogenous settings under settings in the materials pane ??? $\endgroup$ – Kittenmittons Oct 11 '14 at 6:31
  • $\begingroup$ gyazo.com/92c844149d3a6b4463751c3e6a8a2e7a < screenshot of my materials pane $\endgroup$ – Kittenmittons Oct 11 '14 at 6:33
  • $\begingroup$ @Kittenmittons Looks like you are using 2.71. Try updating to 2.72 :) $\endgroup$ – gandalf3 Oct 11 '14 at 6:41
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Yes using two materials is the right choice. in cycles render, very simple setup. Just a simple glass shader, colored blue, and an emission, yellow-white.

adjust the roughness and lighting for tweaks.

enter image description here

enter image description here

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