Penny displacement

[Lamster]

Ok man, here's a rather quick and dirty way.

what you want to do is to go to photoshop and turn the penny reference picture to a grayscale pic. Try to adjust the tone so that the general colour is 50% grey. Make sure you have your penny's hard edged areas pathed out using the pen tool and filled with white with feather at maybe 1 pixel. For the more organic bumps, use the dodge tool to paint the areas that are supposed to be bumped upwards.

You have to take note that displacement for mental ray seems to be affected by the scale of the bounding box of the object. So go to the penny's shape node and under the tab Displacement, make sure Feature Displacement is on. Mental Ray Approx won't work if it ain't on. Then hit the calculate bounding box button. Now make sure that your displacement value is in the same scale as your object. If your object is scaled to 0.08 and you have a displacement map with 1 as your displacement values, you're gonna get a seriously out of wack render. I'm not entirely certain about this, but I've encountered this problem before and I'm just warning you it can happen.

If you are using Mental Ray, go to Windows->Rendering Editors->Mental Ray->Approximation Editor and open the dialog box. Select you penny mesh and hit create on the row that says Displacement Approximation. Now, hit the Edit Button to let the DisplaceApprox attributes appear on your attribute editor. Set the Method to Spatial and the Type to Fine. Now the only values that matter are Max SubDiv and Length. Min Subdiv does jack as far as I tested. Check View Dependant ON. Set your Max subdiv to something like 5 and your Length to 0.25 to begin with and hit render.

Tweak around until happy.

Terence

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