How about partial Smoothing Modifiers?

Second Technician Rimmer

I was trying my hand at sitting a girl in a bikini on a hard surface, with her hands supporting her as she leans slightly back. It occured to me that a smoothing modifier would work very well on her bottom but would mess up her hands. Is there a way to make the modifier only work on her butt and no other part of her body? 

Richard Haseltine

No, not that I am aware of. I did feature request the ability to weight-map Smoothing Modifiers, as I'm sure others have, but I have no idea if the smoothing algorithm would even support that.

Second Technician Rimmer

Thank you for letting me know, Richard. Ideally, such a thing would work with the geometry editor too, since that one allows for polygons selection... imagine that: you "paint" an area and define that this bit can be smoothed. It would solve so many things x_x especially since each "painted" area could be identified separately, allowing for multiple collisions between different things. I hope one day such a thing gets made.Dformers only take you so far...

Syrus_Dante

You can create a morph from a shape that was made with the smoothing modifier and collision. Export an OBJ of the posed and smoothed figure in base resolution hide everything else in the scene, the collision will still work with the hidden collision items. Take into account that a squished butt not just compresses but also maintaines volume so you would need to add a DFormer and scale it up to compensate the compression maintaining the volume.

Next add a second DFormer to the figure and switch it to weight map influence. You can do that by selecting the DFormer then activate the Node Weight Map Brush tool and open the Tool Settings pane. There will be a Unused Map called Influence, press the button Add Map. The default sphere influence of a DFormer is best placed on a figure in default pose but once you set the DFormer to Weight Map the DFormer Field placement is ignored and you can paint the influence on the weight map with the brush dircetly onto the figure where lateron the smoothing should be applied.

The idea is not to use the DFormer to shape the mesh but to select the Weight Map influence in the extended options called Attenuate By of the Morph Loader Pro while you are loading your "smoothed" shape exported OBJ. The DFormer Weight Map influence selected in Attenuate By orption will add the smoothed shape only on the pained area of the figure.

This method is a bit more complicated with the extra step of exporting but will allow you to partialy smooth the mesh and load the collision shape. Also you are limited to the figures base mesh smoothing if you want to load it as a morph. If your figure was exported with a character shape and poses applied also don't forget to select Reverse Deformation in the Morph Loader Pro options.