Fully Transparent Material with reflective Parts

Hello to everyone who reads this,
I want to create a Rain Effect by using static meshes with an animated material.
The problem is that I want the Rain Drop Material to be fully transparent with reflective areas on the Raindrop parts of the textures instead of having a bright base color with cubemap reflections on it.
I would like to have a rain like the Batman Arkham Knight Rain so I also would appreciate any tips on how to achieve the rain drops effect on the player mesh.


Is there really no one who has an idea on how to create such a material?

If you want pure reflections, then make your material additive, and plug the reflections you want into the “Emissive” slot. (“Emissive” really means “add this component to the output framebuffer color” which is what reflections do.) You will have to sample the scene reflection texture manually in the material.
I’m not sure that will get you where you want to go with the actual look, though. You may want to analyze the look that you want in very much detail (how much is reflection, specular, diffuse, refraction, …) to figure out how to build it.
I e, there are two separate questions here:

  1. How did Batman Arkham Knight build their rain, in a theoretical “material function” sense?
  2. Assuming you know the material function you want, how do you achieve that in the Unreal Material editor?

All you should have to do is make a default lit transparent material. Specular reflection is unaffected by opacity and base color for non-metals. You can also turn on screen space reflections in the material properties, though it will cost a lot if you have overdraw. You can use the the specular channel to mask out areas you don’t want to be reflective.

After some testing I’ve got very close to the look I wanted by using the refraction effect of the translucent Material shading combined with an alpha mask but I’ll still take a look at you suggestion. Your’s might gives me a lower shader complexity compared to the method I an using now.

Another question I’ve got is how to create a dynamic raindrop effect that can be faded in and out without needing to change every material. Is there any way to create this with a deferred decal that only affects skeletal meshes?

EDIT: I should add “Rain Effect” to the topic title but I can’t find an option to change this. Is this supposed to be like this?