Flow Map Help

AverageAce

Hey guys,

I really want to implement a Flow Map into my project, but it's starting to seem a little overwhelming. I've been pouring over both Phill Johnson's Flow Map tutorial and Alex Vlachos' Siggraph 2010 presentation on the subject, but it's just not clicking. Most of it has made sense up until the actual flow map itself. I'm not sure I'm fully understanding the implementation of what looks like a height map in Phill Johnson's tutorial on step 3 (http://phill.inksworth.com/tut.php). If anybody could somehow find a way to break this down for a beginner that would be amazing. Thanks again guys!

Ace

Swizzle

The only really difficult part of implementing flow maps is actually getting them working properly instead of just making your texture into pixel soup. The flow map image itself is pretty simple:

The brightness of the red channel controls how fast things move on the x-axis.

The brightness of the green channel controls how fast things move on the y-axis.

The blue channel is generally unused.

Bright spots cause the texture to scroll quickly and dark spots to scroll slowly.

The Polycount wiki has some useful links and info on creating flow maps: http://wiki.polycount.com/FlowMap

AverageAce

Awesome, thanks! I'll take a look.

MaVCArt

As far as creating the actual flow map goes, you may want to use my script: (sorry for the self plug)
http://www.polycount.com/forum/showthread.php?t=97215

To understand flow maps i basically started looking at them the way I look at normal maps: the color information on the map is taken, and used to calculate a new value combined with some other element in the scene. For normal maps this applies to lighting: the color information of the channels is used to recalculate the lighting angle on a pixel-by-pixel basis, based on that color information.

flow maps do largely the same thing, except with the UV channel: they influence the UV's of your model on a pixel-by-pixel basis by offsetting them using the values stored in the channels of the "flow map" which is basically nothing more than another texture.

edit: just saw Swizzle's comment, that's a really good one