FX Filter (Part II)

Autodesk Smoke Tips & Tricks - FX Filter (Part II)

Refer to FX Filter (Part I), if you haven't read the 1st part.

Meet our superstar once more, here's the pictures before any magic numbers is applied.

Try put this number in,

This mean, take the current hot seat pixel, and subtract it from the above pixel value. Say current pixel value is R100,G100,B100, the above pixel value is R40,G40,B40, the result will be RGB60.

Here it become 'find edge' filter, wonder why ?
The reason behind this is, let take a look at the superstar's t-shirt, the whole area of the t-shirt is similar almost the same color (RGB), so when you subtract something similar say Orange R105, G065 - Orange R100, G060, will equal to R005, G005, it will be almost black. And, same with the whole face area, it will be almost black. When it comes to the high color contrast area (RGB) like the edge of T-shirt, The edge between two complete different object, the RGB value will be a huge different, so the result will be some big numbers, and you will see the outline. That's the concept of find edge or outline.

Of course, you can subtract from other surrounding pixel too, not necessary just the above pixel. And you can subtract a bit from left, right, top, bottom as well.

Understand the concept, you can create your own find edge or outline filter.

FX Filter Part III coming soon..