# How to achieve white "fog" effect within an ice cube?

I modelled a set of ice cubes. I'm content with the result, but when I look at an actual ice cube from my fridge, it has a white foggy cloud within, like a microstructure. I'm trying to recreate that effect. For this I created some spheres within the ice cubes and applied a Volume Scatter material with density 1. This won't work. The result is gray and faint. I also tried the Volume Absorption, but it turns grayish too. I really need something more whitish, but not using the Emission shader. Also it has to be like a cloud, more opaque in the middle, more transparent on the sides (maybe some Fresnel here?). Anybody has an idea how to do it?

Here is a photo, the best I could get. As you can see its pretty full of this white microstructure, not very transparent.

• could you possibly share a photo of the ice cube from your fridge as well, and maybe a blend of one of the ice cubes on blend-exchange.giantcowfilms.com ? Then it would be easier for us to try out things :) Commented Aug 17, 2016 at 16:37
• Probably worth mention Gleb Alexandrow's tutorial about How To Create Realistic Ice in Blender Commented Aug 17, 2016 at 17:20

Here's a try using point density for the fog effect.

There are two cubes in the image, I just beveled them slightly, the outer cube's material is basically a glass setup, except that I used an image texture to affect the roughness, and add some variation to the surface structure.

Some explanation on the light path and math>maximum nodes, in the ice material setup:

The light path node determines what type of ray is currently being traced, and by using the Math>Maximum node, outputs 0 if it is not the specified ray connected to the math node, and 1 if it is for the corresponding socket of the mix shader. (0= top socket, 1= bottom socket of the mix shader). If either shadow, or reflection rays are traced in this case, then the maximum node outputs 1, and the material uses the transparent shader. For all other rays, it returns 0, and uses the glass shader. Using this setup provides more transparent shadows, which is desirable here as we have a second object inside the first.

Here is the node setup for the 'outer cube':

The second cube, which is the inside the first has a particle system attached to it. The particles are set up basically at the default settings. I only increased the count to 2200, and set the end to 15. Experiment here, and have fun with it. Here is the final distribution of the particles on the rendered frame from my example below:

The point density material, is added to the 'inner cube' object. The setup is as follows:

The additional Math>Add nodes after the Multiply are optional, but give more control over the material. I used them to adjust the brightness and density of the particles individually, rather than using the Multiply node alone, as that affects both together.

Also, if you really want to avoid using an emission shader, just use the volume scatter, but I personally found the emission shader to have a nicer look.

Here is the result, it's not perfection but perhaps it will give you some ideas to experiment with.

• nice approach! never thought of point density before Commented Aug 20, 2016 at 5:32
• Very nice! May I ask you to show the particles final distribution and say a few words about the Math node after the light path? What's the difference from using "Is shadow ray" only? Commented Aug 20, 2016 at 11:08
• @Carlo, I've made some edits, let me know if anything else should be clarified. Commented Aug 21, 2016 at 3:45

give it a volume shader with a procedural cloud texture