After rolling my own shader with VOPS, I have become interested in learning vex. What's the best way to start? Are there any good tutorials or books out there?

Depends on what you already know.

If you don't know programming in general, you should probably pick up a book/tutorials on plain C.

If you know programming, but not shader programming, your best bet would be to pick up a book/tutorials on Renderman shading language, as it is somewhat close to vex and will get you familiar with the basic ideology.

If you know shaders but not vex, there isn't too much. There is an old but still applicable mixed vop/vex tutorial from Andy Nicholas [andynicholas.com]. There is some code scattered around forum threads, for example Mario's wonderful glass thread [forums.odforce.net]. Then of course you can “View VEX code” by right-clicking on any vopnet-based shader. It will show you the code generated by that network.
Of course there is also the documentation [sidefx.com].
Also a thread on books [forums.odforce.net].


eetu.

I have a question.As you see in these pictures points were cut by using Black and White Image. So, I want to do same by using wrangle. Can anyone type wrangle code to do that?

Here are some vex lessons you can find on SideFX.com/Vimeo

Jeff Wagner

Houdini VEX - https://vimeo.com/173658697 [vimeo.com]

Houdini VOPS - https://vimeo.com/219038609 [vimeo.com]


Rohan Dalvi

Intro to VEX 1 - https://www.sidefx.com/tutorials/intro-to-vex/ [www.sidefx.com]

Intro to VEX 2 - https://www.sidefx.com/tutorials/intro-to-vex-2/ [www.sidefx.com]

Koster Manuel

VEX Wrangles - https://www.sidefx.com/tutorials/vex-wrangles/ [www.sidefx.com]

if(@textureData == 0)
{
removepoint(geoself(),@ptnum);
}

whereby @textureData is the texture value attribute