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I've just recently begun to use displacement in some projects and I'm now
thinking about another upcoming project where I'd want to show a pebble like surface.

Looking for opinions on how far, given a decent grayscale map, can displacement go creating a 3d look of something smooth like river rocks (pebbles)? If it can be done, is there a preferred way of making a grayscale map?

Also, how far can displacement go when intersecting an object -- is it possible for displacement to make an object appear to be embeded in the displacement.

The idea of having to model and randomize lots of pebbles is not the most appealing, so...

Thoughts on the subject much appreciated.

jvm

You can use displacement for pebble like surfaces with ease, here below is one example i created a while back. It shows what you can do.. but there are other similar examples can you find on the MXM Gallery.



/ Max

Max,

Firstly; this is a very, very impressive material.

I remember seeing this when you first did it and it looks like the pebbles actually undercut but obviously this is impossible with a height map. How did you achieve this effect or is it just an optical illusion?

Ozzie: Thank you yes it looks like some pebbles do slide under others but that's more of an illusion because you cannot do that with standard displacement, you can achieve that effect with Modo's vector displacement feature. However you can still fake a similar look by carefully painting your maps in a way so you shade the parts that will undercut other parts slightly darker, it's difficult to explain like this but think of how roofshingles lay ontop of eachother and a displacementmap for such roofshingles would look like fishscales where one scale fades in under the other and so on..

This is what the dispmap for the pebbles material above looks like, it could use a bit of retouching to improve the look of the pebbles but for a relative quickie it's kinda neat.



Btw, a download link to the above pebbles mxm is here for those of you who wanna play with it.
http://maximus3d.net/files/MXM_River_Pebbles.zip

/ Max

Max,

thanks for the explanation and thanks (very much!) for the material. I'll have a look inside and see how the magic is done. Cheers.

Maximus3d-

Thanks for the mxm and your thoughts.

Attached is a quick render of an object with the pebbles...trying to better understand what is happening with the mxm --
been playing around with the settings, and still haven't quite figured it out.


jvm

some hints:
- subdivide the object/surface that is going to be displaced. I guess in this case the rectangles in the mesh should be like 10x10 millimeters to achieve a nice and quick result.
- lower the height, h= 0.6 is at least 3-4 times more than you need in this case.
- don't use a larger surface than neccesary for your renderings.

Why are there a holes in the surface where the cups are?

KurtS-

Thanks for the hints.

The opening in the surface -- just curious to see if it makes any difference in how the cup works with a displaced material.

jvm

Here's an update to the pebbles...

Trying to figure out what might be causing what appear to be striations in the pebbles?


jvm

What precision are you using? Have you tried raising it?

Bubbaloo-

Thanks for your point...here's an updated image.

Seem to get a ghosting effect, but overall very pleased.

jvm

It could be specular highlights which exist in the material, you can get rid of those with a couple of small adjustments. I only added that to get a certain "wetness" to the pebbles.

/ Max

Max-

I see the corresponding pebbles on the displacement map...is it a matter
of isolating the area in the map or making a change at a higher level?

jvm

I'm not sure, btw this is not a tileable material if you're trying to tile it..

Here's an updated version without specular highlights, you might have to add smoothing to the displacement if i forgot that.

http://maximus3d.net/files/MXM_River_Pebbles_2.rar

/ Max

Max-

Thanks...wasn't necessarily going to tile it and now that you mention it, I won't .

jvm