I am using Sydney and a summer dress that is conforming the dress fits nicely.  I ensure that the joints are copied and when I move the legs/thighs Ithe conforming dress moves with the legs as expected.  This is accomplished via the dials etc.

Once I apply a pose or import a BVH for animating the figure.  The dress stops conforming to the movements of the legs.  How come?

I know that I can do a workaround by converting the Conforming to an OBJECT and then to Dynamic.  I really don't want to do that.  I just need the dress to move along with the legs like conforming pants.  Thoughts and suggestions appreciated.

What version of Poser? Does it include the morph brush???? I'm running 2014 Game Dev and have yet to see a pokethru that the morph brush couldn't fix in about 10 seconds.

If you do not have a later version of poser, try adding a magnet to the offending area and pulling the horseshoe in the direction you want the clothing to go.

Why?  Because it is conforming.  The only way conforming dresses work is if they have the exact movement morphs in them that you need.

The reality is that if you are using dresses that go beyond the middle of the thigh, your best results are with dynamic.

I'm using Poser Pro 2012.  IT seems strange that when you translate the thigh or buttock that the dress moves with them regardless of how far you translate.  The BVH is not putting any extreme bends on this at all but the dress igrnores the bend/side-to-side.  Conforming pants don't have this problem.

Look at how the dress is rigged - a lot of them don't go beyond the hip or thigh.  The fact that the dress goes beyond the hip doesn't mean that it was rigged beyond the hip.

I rarely make a conforming dress myself, and when I do I go with what PhilC taught me. Below the hip, I use helper bones.

This is why so many dresses have "movement" handles or additional movement morphs, which you may need to dial in separately to get the dress to move.

GIven the nasty stretching on the side to side movement, I would still try to use just the "hip" of the dress in the cloth room. (When asked for the object to clothify, you simply choose the hip of the dress and go from there. Make sure not to choose Sydney's hip, though, or the results can be sort of... scary.)

In the first image are you posing the buttock or the thigh? How about the second? Bending the thigh will have no effect on the hip, this will be true for both the figure and the dress.

For this dress I would probably go with the solution already mentioned, import the dress obj file and use it in the cloth room.

Thanks everyone.  It would seem though to me that the results should be consistent.  When I grab the thigh and do a side to side - the dress goes with it.

PhilC - in the first image I am moving the thigh side to side using the dial.  See that it is hilighted in RED.

The second image shows you what happens when the BVH is imported and you advance through the animation.  The leg just poke right through ignoring the dress altoghether.

When I import a BVH   - the dress doesn't move.  What is the difference?  The thigh is still translated as a result of the import but nevertheless it doesn't seem to work with the dress. 

I'm not familiar with BVH files, but, in your first graphic, I also note some poke through on both breasts, and looking at the hem, I'm also not familiar with the nomenclature of womens clothing, the side to side is working on what I see as the hip, and the lower part isn't following it.  I'd have to go with the Wiz, conversion to dynamic will probably be the easiest way to cure it. you might be able to treat it as a hybrid, top conforming and skirt dynamic.  Making it dynamic should eliminate the poke through at the breasts as well.  I usually dial the nipples back to zero anyhow, then they don't poke through.  The mesh in that area of the dress may be too coarse to properly collide.

Doric.

What dress is that and where did you buy it?

It's called a "summer dress" and I think I got this off of PoserWorld a while back. i had it in my library.

Are you sure it's for Sydney?  I just checked, and for the G2 female, there is no summer dress.  If you used the fitting room, that might explain it, the other is, most of Poserworlds longer dresses are either fully dynamic or hybrids, But I have no idea how that would work with a BVH, as I don't use them.

Doric

Make the dress a hybrid. Apply BVH to figure. Set dress to collide with figure in Cloth Room. Run sim. Cloth will follow figure. Done.

Yes doing the CLOTH room thing fixes the problem.  This is a Wardrobe Wizard resulting file I think from Jesse - converted to fit ol' Syd.

 
 Some poke through, especially  in upper body can be easily cured, without fiddling with Dynamics, Cloth Room,  etc. Get it as close as possible with whatever usual adjustments you have, and at rendering stage, simply turn off the Visibility on the body part that's poking through. Simple - no poke through :)

Also, remember with some styles of clothing in real life, especially tight dresses, that body movement IS restricted . So..don't go for exaggerated movement poses