I'm trying to extract the point transform values of a wire object in dops, can't seem to get much of any of the dop expressions to work and the point expression doesn't seem to connect either

So, I'm very unclear on how these various dop expression functions are referencing these dops' information. Is this info in the “Geometry” a feild or subdata, … do I use “P” or a number .. and what are these “basic” and “options” about?

I'm sure there is a very clear order to all this but it hasn't clicked yet after almost 6 hours … any help would be great

How do you want to use the information? I'm not actually sure how - or if - you can directly access point information (that is, geometry) with the dopfield command. But you could do it with the point() function, in the SOP context, if you use an Object Merge SOP to grab the wire object out of the dops sim.

So, what are you trying to achieve? Maybe there is a simpler way than what you are trying to do.

well, I got it to work … I'm sure there is a way to do it as I'm still unclear on how dops info is organized. Does anyone know of a good resource as to what exactely is feilds, subdata, etc … and how it is represented in the details view.

I was making wires bound to points on other wires. I didn't want the wires to “snap” to the other wire once the simulation started, so they needed the same offset as the difference between the object and anchor points.

So, I was trying to automatically set an offset of a wire constraint, based on a point on another wire. There were a lot of these so I didn't want to waist time, but in my effort to figure it out I'm sure I blew far more, I did make a digital asset to automate most of the process though.

Do you think I would need to go into sops to make expressions for this?

I'm pretty sure that you have to bring the geometry back into a SOPs context to reference it directly, either by Object Merging it from the simulation, or by using a SOP Solver within the simulation (or a Script Solver, I suppose). But I'm not actually sure about that, so I'm going to look into it more.

It's not easy being this dumb. I knew this, and completely forgot it.

You can access DOP geometry directly using “point”, “prim”, “npoints” or any other SOP expression function. Instead of specifying a SOP path as the first argument, use “/obj/dopnet1:dopobject/Geometry”, where “/obj/dopnet1” is the path to the DOP Network or any node inside the DOP Network, “dopobject” is any string that specifies a DOP Object (an object name or object id), and “/Geometry” is the path to a piece of geometry data on the DOP object (usually this will be /Geometry, but it doesn't have to be).

In general, any place in Houdini where the software is looking for SOP data, you can substitute the “/obj/dopnet:dopobject/Geometry” syntax. One good example of this is the Source POP - instead of referencing a SOP someplace, you can reference a DOP object directly.

ah, yes I knew it was something obvious like that … it would be cool to have a few more examples in the dop's expressions o well

thanks a bunch

The Magic of Houdini has some examples with this syntax in chapter 12, if I remember correctly.