Ue4 flowmap setup?

[HUN0]

Hi, I have been trying to setup a flowmap based material in ue4 and got into a problem

this is a basic flowmap created with flowmap painter, and following is my setup:

and the result was kinda strange: the part which flow is suppose to be 0, looks like it isnt
the whole texture was moved diagonally.
would there be any mistakes I made? by far as I know, subtracting 0.5 and scaling up by 2 will make the data from -1 to 1: when it is added to texcoordinates, it should be flowing with flowmap’s vector
I do need help with this

[alex.underhill]

I’d import it/set it as a normal map so all that’s done for you, if the option’s available.
Else you want to Multiply by 2.0 and subtract 1.0. Gets you to 0.0-2.0 range, and then -1.0 to 1.0 range.

Also verify that your maths is correct by first creating the flow texture as pure zero (0.5,0.5,0.0) and check that there’s no distortion. Flow map does look fine though.

[Mederic]

Problem is likely the ordering between mult and adds which is supposed to be (Input + Bias) * Scale = Output

You can try to remove the constant bias node and simply do the math with math nodes. As Alex said, I suggest also doing MaskRG > mult by 2 > subtract 1 > add to UV. And see if your problems remains.

[simonschreibt]

Also make sure you’re unchecking SRGB on your texture import settings and sample it as “linear color” iny our material.

here is a complete video about the process:
https://www.youtube.com/watch?v=tEr3NE_XLbc

[HUN0]

Yes! unchecking sRGB and multiply 2 then subtract 1 has solved it.
I am curious why the order is important. *2 -1 and -0.5 *2 looks same to me
anyway, thank you all!

[simonschreibt]

multiplication is executed first.

1 * 2 - 1 = 2 - 1 = 1
1 - 0.5 * 2 = -0.5 * 2 = 1 - 1 = 0

But the const.bias node uses the correct order.

If I have to “unpack” by myself, I do * 2.0 - 1.0