Hi

I am trying to drive colour values of a Color SOP using a basic chopnet. I can get CHOPs to drive attributes at the OBJ level but not drive anything within the Geo node or below. I have tried to do it the other way using ch() but can't get that to work either.

Any help with this would be very cool.

Thanks


Dave

There a huge amount of very important documentation regarding CHOPs and their workflow which is simply missing from recent versions' (8, 9, 95.).
You can check the following parts which are fortunately still there:
http://www.sidefx.com/docs/houdini9.5/ref/windows/channelexport [sidefx.com]
http://www.sidefx.com/docs/houdini9.5/expressions/ [sidefx.com] (scroll down to CHOPs section).

Dragos

daverobinsonUK1
Hi

I am trying to drive colour values of a Color SOP using a basic chopnet. I can get CHOPs to drive attributes at the OBJ level but not drive anything within the Geo node or below. I have tried to do it the other way using ch() but can't get that to work either.

Are you using an export chop? If so, make sure to toggle on the export flag. In the export chop make sure the path is set to the node you want to override and the path is the name of the attribute.

cheers,
Rob

Yes I have the export nodes in place with the export flag turned on.

I am trying to drive colour values of a Color SOP using a basic chopnet.

You can't use the Color SOP because it doesn't support local variables. In order, to use CHOPs to drive SOP attributes, you need to be able to index into a different frame of the CHOP per point. So you can use the Point SOP which gives you access to the $PT local variable along with the chopf() expression to obtain the color values from the chop network.

A far better way though is to use the Channel SOP. I've included both methods in the attached file.

Excellent!!

Thanks Ed

Much Obliged :-)

edward

I am trying to drive colour values of a Color SOP using a basic chopnet.

You can't use the Color SOP because it doesn't support local variables. In order, to use CHOPs to drive SOP attributes, you need to be able to index into a different frame of the CHOP per point. So you can use the Point SOP which gives you access to the $PT local variable along with the chopf() expression to obtain the color values from the chop network.

A far better way though is to use the Channel SOP. I've included both methods in the attached file.

Maybe I missed something in the original query but you can still have the Color SOP driven by a chop network, no?

Sure, if you want all the points to have the same color.