Subtracting alphas problem

TimeSpirits · February 11, 2015, 6:49am

I have two world aligned blends, one controls the height of the snowline, the other is where the rock faces are(where no snow should be).

The idea I had was to subtract the rock face blend from the snow line blend. The following image shows:

Top - snowline alpha
Mid - the rock faces (where I DONT want snow)
Bot - the result of subtracting the mid from the top. This is obviously not what I expected. Notice the bare valley of grass is now covered in snow.

Here is my material:

I tried using the Clamped input and various other things but none seemed to work.

I’m willing to try other ideas to achieve the same effect as well.

anonymous_user_2ed5b4c7 · February 11, 2015, 9:03am

Hi!

Subtraction is not right way. Because you can get undesired value like negative value or added value. For excluding some regions in mask, you need use multiplying.

TimeSpirits · February 13, 2015, 4:01am

Thanks svv3dUDN. I actually just figured this out and got an ok solution. I did not use multiply, was able to lerp together both masks as one minus, and used the alpha of the gradient one as mask.

The other thing I found out was you do need a Static Bool in the Clamped input set to true for this to work.