I can't find any actual cracks in the mesh. Material is a simple colour only. Lights are three spots where top one has shadows on and raytraced.

Advice appreciated.

Tiny your mesh is too high res. I know that sound weird but the cloth room will work better with a lower res mesh and your "black cracks" will go away.

Provided the mesh is properly welded and the black cracks are not actually cracks in the mesh, try the morphbrush and smooth that "cracked" areas a bit.

Looks like the normals are messed up because the mesh intersected itself while draping.

And yes, this can happen more easily with high res meshes than low res meshes.

First try "Normals_Forward" in the material settings.

If the cracks go away, then it's a normals problem and smoothing with the morphbrush should fix it, as it will re-arrange the normals.

Alternately, could it be poke-through from the horse's fur?   Are the black areas still there when you hide the horse? 

Looks like the mesh folds and is intersecting with its own folds.
Try lower resolution mesh, and put folds in a sisplacement map.

When a cloth sim makes the mesh intersect with itself the only way out is to stiffen the cloth (reducing the folding) or go lower res mesh and with a displacement map.

My guess would be a combination of Shadow Min Bias too low, plus the mesh construction itself.

When the Min Bias is too low, polys can end up casting individual tiny sharp shadows. Is it set to the default 0.8 on the spots or is it lower? Also, depending on the version of Poser, I've had unexpected results in later (P9 & up) versions when using spots with shadows set to anything other than 1 (though I don't think that's the issue here) - are the shadows on the other two spots on or off?

When using dynamics I've found that a regular grid of quads will give a sawtooth-looking result as soon as a fold goes against the poly flow. What I mean is that the poly flow on the mesh here is all in straight lines. Bending only happens at the edges. When a fold runs against that it it looks like stairs or a sawtooth pattern. If the fold is large and subtle or the mesh is very high-res it won't be very apparent, but when either the mesh is low-res or the fold is small and sharp, it becomes very obvious.

A close-up render of the problem area - plus wireframe too - would be interesting to see if possible.

I don't guess. Bagginsbill and I reserached this issue thouroughly about two years ago. I documented the findings, http://www.book.artbeeweb.nl/?p=632 . It;s somewhere in this forum too, in some very lengthy Cloth Room for Dummies threat.

Note that this page is in the middle of the "how to get your PhD in Cloth Simulation" so you might need some asperine as well :-).
Also note that this part on Cloth Dynamics starts at http://www.book.artbeeweb.nl/?p=594, you can download the entire PDF from there, the section mentioned is on page 70.

In short: this kind of cloth behavior, ridging and crumbling, happens especially in quad meshes. Not using quads resolves the issue, smaller quads make smaller ridges. And... 

"Increasing shear and/or fold resistance will push the crumbles out. But high shear and fold resistance will affect other behavior of the cloth as well, life is a compromise. Reducing mass (density), friction and other effects will make this pushing more successful. So instead of raising fold/shear resistance, reducing density is an option. And as shear and fold resistance work together in this case, you can do with less fold and more shear."

Notes on other posts:

 - perhaps not very intuitive, but higher resolutions make finer, thinner, more flexible cloth. Low res makes coarse, thick cloth behavior. Lowering the resolution will not make less ridges, but perhaps might make them less apparent.

 - Min Shadow Bias addresses the shadowing on displacement mapped surfaces, and e.g. prevent skin (brick, etc) pores to make shadows. Has nothing to do with cloth behavior. Sorry. Raytrace Bias (in the reflect node) does a similar thing for reflections on a displacement mapped surface.

All the best.

Pardon me if this is considered a hijack of the thread, Joe Public mentions welding. I think I understand welding inside a my 3D modeling app. What I don't understand or never found explained exactly what happens when you weld inside of poser.

You have Weld Group inside the Grouping tool

You have weld body part seams on wavefront object export

I have a confroming peice that I will say is modeled poorly when looking at it in wire frame view inside of poser as it has cracks in the mesh. I am on my lap top for another week and don't drag C4D around on it vs my home desktop computer. So I will have wait to fix it till I get back home.

I assume that Poser does not add points or or creates polys to fill the gaps. But what exactly do those two welding options in Poser really do?

If these needs to be a new thread, then I will move it to a new thread if those in the know feel it will erupt into a debate and not a single informed response.

Thanks

Gary

Maybe I should have been clearer. I know Min Bias has nothing to do with dynamics. The little black artefacts in the top image posted look like they could be the kind of artefacts you'll get on any mesh in Poser with a very low Shadow Min Bias on a light - individual polys casting their own shadows.

Whether that is the issue here I'm not sure, but I've had something that looked similar in my own renders a few times, and that was the culprit.

If Min Bias is the problem, it could also be exacerbated by the jaggies that will result from using a regular grid mesh as a dynamic item.

So in short I think this is primarily a lighting issue, though I could be wrong ;)

Quote - Looks like the mesh folds and is intersecting with its own folds.
Try lower resolution mesh, and put folds in a sisplacement map.

When a cloth sim makes the mesh intersect with itself the only way out is to stiffen the cloth (reducing the folding) or go lower res mesh and with a displacement map.

Exactly. I've just gone through this same issue with a person on another board. Simply lower the poly count and the "cracks" will go away.

I've found that upping the Crease Angle under the prop Properties tab helps with a certain kind of cracks that seems to be due to the angles on the mesh being too sharp. It might turn up on heavily folded cloth without there being any discernable intersections.

I can't tell if this applies to your problem, but it might be worth a try. :)

Wow guys! I didn't get any info about replies, am very grateful for all the suggestions and will directly try them. Will be back with results.
Thank you so much. 

Oh I found another one!

If you have Wings3D, load your .obj file in and check if there are any hard edges. Set all the edges to soft. I recently used this method to fix cracks on a dynamic item I am working on. :)

Lowering the poly count solved my problem. Thank you everybody!

Frequency, I do the modelling in Wings3D and will test that setting. Thanks!

Glad I could help as I really like your animals.