<p>According to <a href="https://en.wikipedia.org/wiki/List_of_refractive_indices" rel="nofollow">Wikipedia</a>, ice has a slightly lower IOR than non-frozen water, though I don't know how much that difference would affect the results.</p>

<p>The "opaque"-looking parts of an ice cube are caused by clusters of microscopic bubbles formed during freezing. You might be able to model those using geometry, but given the scale and number I suspect that some kind of participating media model would probably be a better fit. (Though I don't know of any.)</p>

<p>Also, remember that most non-submerged ice you'll see is going to very soon form a thin layer of liquid water interfacing it with the air, so this might significantly alter its appearance too.</p>

CC BY-SA 3.0
2015-08-10T20:17:10.753Z
2015-08-10T20:17:10.753Z
yuriks
<p>I've found that bump mapping when calculating lighting and refraction rays can add a lot to the look of ice. It makes the ice look textured and imperfect, like a melting ice cube would look.</p>

<p>I sort of wonder if maybe animating a bump map could help make it look wet, as water sheets / droplets ran down it's surface.</p>

<p>The images below look pretty nice, but they would probably look even better with the internal imperfections that other people are talking about.</p>

<p><a href="https://i.sstatic.net/t5t5K.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/t5t5K.png" alt="enter image description here"></a></p>

<p><a href="https://i.sstatic.net/4NJbX.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/4NJbX.png" alt="enter image description here"></a></p>

<p><a href="https://i.sstatic.net/sPo4R.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/sPo4R.png" alt="enter image description here"></a></p>

<p>Here's my shadertoy where I got the screenshots from: <a href="https://www.shadertoy.com/view/ldj3zz#" rel="nofollow noreferrer">https://www.shadertoy.com/view/ldj3zz#</a></p>

CC BY-SA 3.0
2015-08-11T11:21:46.560Z
This seems close to being a link-only answer. Could you include an explanation so that this can be understood even without following the link?
trichoplax is on Codidact now
CC BY-SA 3.0
2015-08-11T15:55:09.820Z
Apologies, you are correct.  I should have given screenshots at least, and it turns out i even linked to the wrong link!
Alan Wolfe
CC BY-SA 3.0
2015-08-11T20:43:49.680Z
Thanks for the images, but it would also be interesting to see an explanation of how this works and why it improves the appearance. A good answer should provide understanding without the need to leave the site - then the links are there for further reading in more detail.
trichoplax is on Codidact now
CC BY-SA 3.0
2015-08-11T20:48:29.437Z
I mentioned you apply bump mapping to lighting and refraction calculations. Would you expect my answer to explain bump mapping?
Alan Wolfe
CC BY-SA 3.0
2015-08-11T21:41:51.340Z
Explain whatever you feel would be helpful. If you are presenting something which answers the question, then you can explain why it helps.
trichoplax is on Codidact now
CC BY-SA 3.0
2015-08-12T00:36:31.713Z
I had an awesome chance to see ice cubes close up today during dinner, and they seemed to actually be pretty smooth and without bumps. I think the vital part of this is giving them that "wet" look.
yuriks
CC BY-SA 3.0
2015-08-12T01:35:33.710Z
Interesting! I wonder what would make it look wet?
Alan Wolfe
CC BY-SA 3.0
2015-08-11T05:57:28.187Z
2015-08-11T23:20:59.580Z
2015-08-11T23:20:59.580Z
Alan Wolfe
<p>Two big ones you're missing:</p>

<ol>
<li><p><a href="https://en.wikipedia.org/wiki/Fresnel_equations" rel="nofollow">Angle-dependent reflection</a>.  This is one possible cause of your "transparent in places and not in others" effect, and the most likely cause of the missing wetness.</p></li>
<li><p>Ice cubes usually have air bubbles trapped inside.  This shows up as a white volumetric haze denser in the center of the cube (for small bubbles) or distinct bubbles (for large ones).  This is the other likely cause of your "transparent in places and not in others".</p></li>
</ol>

<p>The techniques for modeling these depend on what rendering method you're using.</p>

CC BY-SA 3.0
2015-08-10T20:16:23.327Z
2015-08-10T20:16:23.327Z
Mark
<p>I can model ice cubes as slightly misshapen transparent cubes with the refractive index of water, but they don't look convincing. They look like lumps of glass rather than ice.</p>

<p>Looking at real ice cubes I can intuitively describe some differences but I don't know what physical properties to change to match them:</p>

<ul>
<li>Ice cubes are wet. Mine look like dry glass.</li>
<li>Ice cubes are transparent in places and not in others.</li>
<li>Ice cubes often have cracks that are visible despite not separating.</li>
</ul>

<p>In this instance I am trying to model ice cubes on a surface (in air, not floating in water).</p>

<p>What techniques do I need to include in order to increase the realism?</p>

<p>I am not looking for real time techniques, just to produce still images. I would like the ice to be photorealistic even close up, and to cast realistic caustics and shadows.</p>

<p>I've tried using curved edges and coating my ice cubes with a thin layer of transparent material to simulate a melted layer of water, but it doesn't seem to give the impression of being wet. I've also tried embedding a transparent sphere half the size of the cube at its centre, with a fog effect, but it doesn't blend into the cube naturally - it just looks embedded. Even a series of nested spheres with gradually increasing fog still doesn't look right.</p>

CC BY-SA 3.0
2015-08-10T22:21:21.550Z
I think you would also be interested in techniques to simulate Rough Refraction such as those described in http://www-sop.inria.fr/reves/Basilic/2011/DBSHR11/RoughRefr_I3D_Final.pdf. Look at the screenshots and see how it could benefit ice cube rendering !
wip
CC BY-SA 3.0
2015-08-10T22:31:17.223Z
@wil While those results for rough surfaces are very impressive (especially for a real-time algorithm), ice tends to be very smooth on the surface, and rough inside - almost the opposite effect.
trichoplax is on Codidact now
CC BY-SA 3.0
2015-08-11T04:44:58.767Z
Maybe questionslike this would require pictures
joojaa
CC BY-SA 3.0
2015-08-11T09:00:35.547Z
Do you want to render stills or animation? If the cube is to be animated are you looking for real-time effects? And yes, if this wasn't the private beta, an image of your current results would be nice.
Martin Ender
<refraction><transparency><photo-realistic>
How can I make my ice cubes look real?
trichoplax is on Codidact now
# How can I make my ice cubes look real?

(Asked by: username_0 on 2015-08-10)

I can model ice cubes as slightly misshapen transparent cubes with the refractive index of water, but they don't look convincing. They look like lumps of glass rather than ice.

Looking at real ice cubes I can intuitively describe some differences but I don't know what physical properties to change to match them:

* Ice cubes are wet. Mine look like dry glass.
* Ice cubes are transparent in places and not in others.
* Ice cubes often have cracks that are visible despite not separating.

In this instance I am trying to model ice cubes on a surface (in air, not floating in water).

What techniques do I need to include in order to increase the realism?

I am not looking for real time techniques, just to produce still images. I would like the ice to be photorealistic even close up, and to cast realistic caustics and shadows.

I've tried using curved edges and coating my ice cubes with a thin layer of transparent material to simulate a melted layer of water, but it doesn't seem to give the impression of being wet. I've also tried embedding a transparent sphere half the size of the cube at its centre, with a fog effect, but it doesn't blend into the cube naturally - it just looks embedded. Even a series of nested spheres with gradually increasing fog still doesn't look right.

**Tags:** refraction, transparency, photo-realistic

> **Comments:**
> **username_1**: I think you would also be interested in techniques to simulate Rough Refraction such as those described in http://www-sop.inria.fr/reves/Basilic/2011/DBSHR11/RoughRefr_I3D_Final.pdf. Look at the screenshots and see how it could benefit ice cube rendering !  
> **username_0**: @wil While those results for rough surfaces are very impressive (especially for a real-time algorithm), ice tends to be very smooth on the surface, and rough inside - almost the opposite effect.  
> **username_2**: Maybe questionslike this would require pictures  
> **username_3**: Do you want to render stills or animation? If the cube is to be animated are you looking for real-time effects? And yes, if this wasn't the private beta, an image of your current results would be nice.  

---

## 3 answers

### Answer by username_4 on 2015-08-10. Score: 3 | Accepted answer

According to [Wikipedia](https://en.wikipedia.org/wiki/List_of_refractive_indices), ice has a slightly lower IOR than non-frozen water, though I don't know how much that difference would affect the results.

The "opaque"-looking parts of an ice cube are caused by clusters of microscopic bubbles formed during freezing. You might be able to model those using geometry, but given the scale and number I suspect that some kind of participating media model would probably be a better fit. (Though I don't know of any.)

Also, remember that most non-submerged ice you'll see is going to very soon form a thin layer of liquid water interfacing it with the air, so this might significantly alter its appearance too.


---

### Answer by username_5 on 2015-08-11. Score: 4

I've found that bump mapping when calculating lighting and refraction rays can add a lot to the look of ice. It makes the ice look textured and imperfect, like a melting ice cube would look.

I sort of wonder if maybe animating a bump map could help make it look wet, as water sheets / droplets ran down it's surface.

The images below look pretty nice, but they would probably look even better with the internal imperfections that other people are talking about.

[![enter image description here](https://i.sstatic.net/t5t5K.png)](https://i.sstatic.net/t5t5K.png)

[![enter image description here](https://i.sstatic.net/4NJbX.png)](https://i.sstatic.net/4NJbX.png)

[![enter image description here](https://i.sstatic.net/sPo4R.png)](https://i.sstatic.net/sPo4R.png)

Here's my shadertoy where I got the screenshots from: <https://www.shadertoy.com/view/ldj3zz#>

> **Comments:**
> **username_0**: This seems close to being a link-only answer. Could you include an explanation so that this can be understood even without following the link?  
> **username_5**: Apologies, you are correct.  I should have given screenshots at least, and it turns out i even linked to the wrong link!  
> **username_0**: Thanks for the images, but it would also be interesting to see an explanation of how this works and why it improves the appearance. A good answer should provide understanding without the need to leave the site - then the links are there for further reading in more detail.  
> **username_5**: I mentioned you apply bump mapping to lighting and refraction calculations. Would you expect my answer to explain bump mapping?  
> **username_0**: Explain whatever you feel would be helpful. If you are presenting something which answers the question, then you can explain why it helps.  
> **username_4**: I had an awesome chance to see ice cubes close up today during dinner, and they seemed to actually be pretty smooth and without bumps. I think the vital part of this is giving them that "wet" look.  
> **username_5**: Interesting! I wonder what would make it look wet?  

---

### Answer by username_6 on 2015-08-10. Score: 4

Two big ones you're missing:

1. [Angle-dependent reflection](https://en.wikipedia.org/wiki/Fresnel_equations). This is one possible cause of your "transparent in places and not in others" effect, and the most likely cause of the missing wetness.
2. Ice cubes usually have air bubbles trapped inside. This shows up as a white volumetric haze denser in the center of the cube (for small bubbles) or distinct bubbles (for large ones). This is the other likely cause of your "transparent in places and not in others".

The techniques for modeling these depend on what rendering method you're using.


---

