Slit Scan / Time Shift Effect File Read Please Help

[trzanko]

Hello,

I'm attempting to create the slitscan/timeshift effect. 

I'm creating a vector array in a for loop, each loop has an attrib from map and a wrangle that appends Cd to a vector array. It works when the attrib from map is always reading from the same file. When I change the attrib from map file read expression to anything that has to do with $F or the meta nodes iteration Houdini crashes. 

I have a test scene that has documentation and even nodes setup to create test frames to work with.

If it is a matter of the way that multiple files cannot be read at once please let me know. If someone knows of a better way to read from multiple files at once and/or achieve this effect please let me know. 

I'm aware that after effects has this effect and uses gradients to determine which frame to look up color from. While that method is great, I'd like to be able to write the gradients/lookups in vex to achieve results. 

Any help greatly appreciated.

 

-T

concept_025_slitScan_v001.hiplc

[Atom]

Your expression in the AttributeFromMap is not needed. Just reference the COP File node.

op:/obj/cop/file[$F]

 

The COP File node itself is already fetching the correct file name by frame.

$HIP/render/concept_025_slitScan_v001.mantra1.$F4.png

 

 

Edited December 12, 2016 by Atom

[trzanko]

Hi Atom, 

Thanks for the reply. I assume that the expression [$F] works for you and does not crash houdini?  Though doing as you recommend and putting [$F] in the attrib from map crashes houdini on my linux box running ubuntu 16.04 LTS.

$F is meant to be the test case that unfortunately seems to crash houdini. The goal is to get it to work by having the iteration of the for loop be the frame that is read, such that the expression in the attrib from map would be op:obj/cop/file[detail("metaDataNode","iteration",0)]. This method would build a vector array, each index in the array then being the frame(iteration) number which would allow me to specify per point which frame(array index) to read from. I could offset the index per row/column of the grid giving the slitscan effect. That's the idea at least.

[trzanko]

This issue seems to have been cleared up thanks to Matt Estela over on SideFX forums by using solver instead of a for loop. 

Link if interested.

https://www.sidefx.com/forum/topic/47387/?page=1#post-212913