K, I’ve set approx style to Delaunay, but adjusting the grading does not appear to change anything in the render…

n8skow [FA]

n8skow 14 August 2008 08:08 PM

I’ve got a couple cubes I’ve applied some displacement maps to - but ‘gaps’ now appear at the edges. Can this be fixed by mirroring the edge pixels of the textures? I’d like to avoid doing this to keep the texture seamless, is there another method?

I’m having this very issue with a scene I’m working on at the moment. My UV maps are nicely laid out for the entire scene. Only where my displacement which isn’t pure black crosses the UV edge it splits. It looks like it’s trying to maintain the flatness of the polygons. I thought it might be normal related so by softening the normal a bit the seams seem to go away but at the expense of adding too much softness to my hard steel plated surface.

I don’t know anything about adjusting the normal’s and the normal tools I have don’t seem to provide what I need. Normally I just set to face while i’m working which also unshares them. I then smooth the object later which takes care of my normal work at the expense of high polygon rates. It would seem that I’m a victim of my strange workflow.

Cheers,.

If you are having gaps, the problem is not your normals. I would try loading your displacment maps into 3D Paint. Paint across the seams to make sure they are completely seamless. Try rendering again.

Todd Palamar
http://www.speffects.com

Thanks. I know they are seamless. I just found another forum post that explained this. The problem it seams is that the normals are set to face. The surface is completely hard and mental rays method of dealing with the displacement crossing the UV edge it to tear it. Presumably to prevent warpage of the image or just plain bad luck. It comes down to just not enough data for it to handle the edge. If I soften the normals it all comes right except that it wobbles the surface removing the whole point of having a flat surface. It has been suggested the best thing to do in this faceted hard object scenario is to add a small soft bevel on the edges to allow mental ray to go around the corner. or build the thing in Sub Divisions.

I was about to try the bevel edges just as I got your post.

Thanks for your input. Cheers,.

ah, interesting. Thanks for posting.

Todd Palamar
http://www.speffects.com

Obviously I’m not completely sure about what I said and we can’t believe everything we read.

I’m not knowledgeable enough to convert it to Sub-D without loosing the hard faces (in appearance) If I build that way in the first place it would be another matter. The bevels, well again it would be a long job to add them all in properly.

What I am noticing is that when the edges are softened (which seems to adjust the normals causing the roundness I don’t want) the splits where the displacement is not neutral (100% black). Perhaps this isn’t as related to normals as I think? Maybe I miss understood that distinctions? Anyway softening the edges added “polySoftEdge#” (angle 180) to the selected objects history, which is the exact same result as using “set normal angle,” (except you choose the angle up front). Features both located in the normal menu.

Not sure where I’m going to go from here.

I must consider this some more another time. Must sleep. Cheers,.

I really hope someone solves this problem because i am having it now too.

It seems like it should be such a simple thing to do ?

Displacement offsets the texture in a single direction - the direction the normal is.

Each pixel from the displacement will head in that normals direction - so when you have 2 faces facing totally different directions, the displacement is simply going to change direction instantly.  I’m having a hard time describing this I’m afraid. 

The easiest way to remidify this, is to put grey (whatever color is “empty") on the UV lines, even a pixel for each side will do.  This should make corners work correctly, as the corner pixels wouldn’t be offset like the ones next to it.