Make sure your shader is scaling the raw values properly. Multiply your colors by 2 then subtract 1 will move them from 0-1 to -1 - +1. So painting with 127 (or 0.5) will be 0 offset. 0 will be -1 offset and 1 will be +1 (or subtract 1 and multiply by 2. A constant bias scale node is what you need. Bias of -1 scale of 2.)
That's because you've set up your material to only work that way. Doing something like subtracting 1 from a colour channel will give you a range of -0.5 to 0.5, which gives you bidirectional panning if you need it. Makes your flow maps harder to author though. It can be. I've seen a lot of people us vector field tools for…
I made a couple Photoshop actions for working with flow maps. First, an action for generating a texture coordinate image like so: Secondly, an action for converting a morphed/deformed texture coordinate image like you would get out of Maya Fluids (just like imbueFX's tutorial) or Photoshop's liquify tool to a vector flow…
Welcome to the technical part of tech art. :) Quick review: an 8 bit value has a maximum integer value of 255. A 16 bit integer has a maximum of 65536. each additional bit increases the range of values by one power of 2. Since our normal textures have 8 bits per channel, using one channel for the lower 8 bits and a second…