[UE4] Z-Axis Oriented Material Issues

Will Faucher

Hi,
So I am working on a moss shader for a project I'm working on.
The purpose is that have the moss show up on the Z-Axis in world-space, so that when I rotate my mesh, the moss only appears on the very top of the mesh. The problem I am having is adjusting the falloff.

The following screenshot shows the current falloff that I am able to set up in the engine. As you can see, the blend goes from top to middle in a perfect gradient.



That results in the shittiness that is this:


Because my rocks are at a slight angle, they show up as completely covered in moss. I need to find a way to tighten that falloff, to something similar as the following screenshot. I want the moss to show up only at the very tip of the top of the mesh.


Ideally, I'm after a result similar to this paintover I did:


How do you think I could go about doing something like that?

Obscura

Use a larger value in the constant3. So like 4 or more instead of the 1. Or simply multiply the constant3 with a large number. Or maybe you can use the power expression somehow.

Khaja

you could recreate the same technique from UDK that allows for parameters for falloff sharpness, angle and coverage. This is in UE4 but uses a UDK technique (that i sadly can't find good non-404'd resources for.



That should help you. Need any extras just ask. (it's controlling an Alpha in a lerp as normal)

nfrrtycmplx

You should dot the up vector against the Pixel Normal WS.

as a post effect you could do the same against the screen space world normal.

http://www.polycount.com/forum/attachment.php?attachmentid=18300&stc=1&d=1405148878

The node is PixelNormalWS

Dot that against your up vector

Then to tighten the mask:

Add 1 to the result and divide by 2 to make sure you don't have any negative values. Then apply a power of X - X being the desired sharpness.

Clamp the result to range of 0 - 1. this will avoid artifacts when using it as a mask.




http://www.polycount.com/forum/attachment.php?attachmentid=18301&stc=1&d=1405148878

Then to sharpen transition from white to black:

Then multiply by your desired sharpness and clamp that result.

Note: In this example you could use only the one clamp and the result would be the same.


I don't recommend using the UpVector against itself transformed from tangent to world space, as the result is the same as if you were to dot against the vertex normal WS. This will result in a "faceted" look in most cases.

http://www.polycount.com/forum/attachment.php?attachmentid=18302&stc=1&d=1405148878

Khaja

nfrrtycmplx: thats a nice way of doing it! cheers for sharing!

Will Faucher

I love you all so much. This is exactly what I needed! Thank you!

JohnHandyArt

Hey, love this shader.
Im using it to set up some moss for the rocks in my scene.

Im having a little trouble using the mask to "Lerp" between 2 normal maps.
It works fine using it for the roughness and Base Colour.

I think its because im using the PixelNormalWS node, I have looked around but cant figure out why its throwing up an error.



Above: This is the set up I have for the mask



Above: Showing the "Lerp" between the base colours working



Above: showing the error that pops when I hook up the mask to the lerp-alpha (the pixelNormalWS is the smae node that is connected to the start of the mask)



If anyone can spot the mistake I am making it would be awesome if you could point it out.

Thanks!
John Handy Art

nfrrtycmplx

Odds are good that you're doing arithmetic between a float 4 and a float 3 somewhere? Without the output from the log and a complete graph it's impossible to see from this image what the error is.

On an unrelated note, why are you multiplying your green channel by -1 in the normal map 1? You can do that in the texture itself and save an instruction or 2. It also looks like you're trying to add detail normal to your surface, which should be achieved through the use of a blend angle corrected normal node (don't have unreal open at the moment to get the exact name of the node, but in the context sensitive menu simply type "Correc" and it will pop up. Hope that helps.