Snippet VOP in VOP COP2 Filter

[j00ey]

I am banging my head on the wall trying to get something that I thought would be very straightforward to work.

 

I just want to remap the luminance of an image in COPS to then use that value for multiplying against some noise. I have a ramp on the snippet . I'm piping R G and B into the VOP from the globals and my code so far is this :

 

vector rgb = set(R,G, ;

vector hsv = rgbtohsv(rgb);

float lum = hsv[2];

lum=chramp("lumremap",lum);

R=lum;

 

It seems the chramp function doesn't want to work as whatever value I put in there instead of lum, it still returns 0. I haven't used the snippet VOP before though I am familiar with wrangles and so on. Anyone know what's wrong here?

 

Thanks

Edited January 13, 2015 by j00ey

[j00ey]

hmmm... ch("parm") doesn't seem to work either. Is this another COPs bug or am I missing something?

 

From the help files for Snippet VOP :

 

You can use the VEX function ch to evaluate parameters. The path is relative to this node (ch("parm") will evaluate the parameter parm on this node). This evaluation will be done at the current time.

Edited January 13, 2015 by j00ey

[Mandrake0]

hi i just made a simple example.

 

you have to put the command in single quotation mark: `ch("testparm")`

 

vopcop_snippet_example_ch.hipnc

Edited January 13, 2015 by Mandrake0

[j00ey]

Great! Thanks so much for the help, never occurred to me to try that.

 

Is that just a COPs thing? I've never come across that syntax in wrangles... or is it snippet VOP specific and if so, why does for instance rgbtohsv work without backticks and ch doesn't?

 

Thanks again 

[Mandrake0]

Great! Thanks so much for the help, never occurred to me to try that.

 

Is that just a COPs thing? I've never come across that syntax in wrangles... or is it snippet VOP specific and if so, why does for instance rgbtohsv work without backticks and ch doesn't?

 

Thanks again 

 

maybe just ask the real houdini it's maybe just magic. :-)

 

i think rgbtohsv is a VEX function the ch("") reads the value from the parameter interface so i'ts not a VEX function.

when you want to use a parameter just RMB copy Parameter and paste (RMB -> Paest Copied Re...) the Parameter in the Text field that should work always. 

[j00ey]

Right I see... tis indeed black magic!

 

Thanks for the copy paste tip also, I didn't realise that worked in VEX fields, very useful