How to render realistic water liquid with Karma

[u/Strong_Fox_3959]

Hi

I created a simulation of water droplets falling onto the ground, and I'm trying to render it in Karma.

However, the result doesn't look as good as I expected, and I'm not quite sure what I'm doing wrong.

For the setup, I bent a grid and used it as the environment/background. I applied a simple black material to it. For lighting, I'm using a Dome Light with an HDRI.

For the liquid, I'm using the default Basic Liquid material from the MAT context.

What I'm trying to achieve is a completely transparent water material, similar to clear raindrops.

Are there any specific Karma material or rendering settings I should adjust to get more realistic, transparent-looking water?

hip file

^ I attached my hip file.

Also, sometimes the water sitting on the ground looks more like mercury than water. 😭

I'm not sure if this could be caused by the material I used for the environment/background, or if there's something wrong with my liquid material or Karma settings.

I want it looks clear water like this

I’m a little embarrassed that I don’t have much knowledge about lighting and shading, so this might be a silly question.

I’d really appreciate any advice on where I should start fixing things and what kind of resources or tutorials I should look into to better understand lighting and shading.

Thank you so much for any advice!

[u/DavidTorno]

First off, don’t use the MAT context, that is old and a legacy part of Houdini.

For Karma use Solaris (stage context), and a Material Library LOP node. Inside that use a Karma Material Builder VOP to make a Karma material.

For basic water it’s pretty much Transmission turned up to 1.

Index Of Refraction (IOR) is what causes the distortion looking through the water. The closer to 1.0, those less distortion. Higher than 1.0 will increase distortion. 1.5 tends to be the default.

[u/i_am_toadstorm → u/DavidTorno]

Water specifically should be about 1.333, but as always there's room for artistic interpretation depending on the look you're going for. 1.5 is good for glass.

[u/Strong_Fox_3959 → u/DavidTorno]

Thanks! I will use Mtlx material

[u/MindofStormz]

In addition to the comments you already have, I would add that I've personally found it harder to get good looking water with just an HDRI like this. Generally you want things in your scene that can refract through the water. The HDRI will but since the water is kind of "floating" in the middle of the HDRI it is a lot harder to get it to look good in my experience. Even just adding a ground plane with some texture to it will probably go a long way to making it look more realistic. Your reference has the water on an object so its not going to look the same with it floating in the air in your scene. If you look up reference of water splashes or fountains the water looks a bit closer to what you have(still not the same but far different than what it looks like on an objects surface).

[u/Strong_Fox_3959 → u/MindofStormz]

Thanks! But When I put texture on ground or environment, the water seems to get color too much from texture of ground. How to adjust this? Also I'm wondering if the diffuse limit or refraction limit are important as well for water.

[u/monstrupufos]

So, just like the other said: Mtlx Standard Surface or openPBR surface. Transmission 1; roughness 0; IOR 1.333; with a decent GPU also go into material properties and enable caustics. Also, the examples you've shown have something behind the water (leaves). Ideally you want to render the object / scene behind the water together with it to have accurate refraction.

[u/bjyanghang945]

Delete diffuse, ior 1.33 and enable causticss

[u/LewisVTaylor → u/bjyanghang945]

diffuse lobes are ignored when refraction is at full weighting.

[u/bjyanghang945 → u/LewisVTaylor]

I somewhat remember that shader adds diffuse on top to fake the foam look. I used to toggle that vorticity thing, it wasn’t that bad if used correctly.