Displacement map giving jagged edges

[bravid2001]

I’m trying my hand at displacement maps for the 1st time. Using Maya 2008, I created a polygon cube and extruded it a few times. I used automatic mapping and created a PSD network in the UV texture editor that includes a displacement map. The PSD is 2048x2048. I added some grey squares to the psd displacement layer and updated the file in Maya. The resulting image gives jagged lines (as I just found out it's called nickeling) in my model where in Photoshop the lines are straight. I’ve played with the alpha offset but that doesn’t seem to help anything. I’ve included a jpg of my render that shows only the area of concern.

Raising the tesselation helps a little, but not enough.

I'm rendering with mental ray.

Thanks 

[joojaa]

Well the size of the texture tells us very little unless we know what the uv coverage on the area is.
Also what dispacement approximation are you using? have you tried fine view dependent 0.5 with a raised maximum splits?

[bravid2001]

I raised the initial sample rate from 6 to 200 and that helped alot. I can still see some jagged edges but for what I'm doing, the result is fine. Thanks.

[joojaa]

I raised the initial sample rate from 6 to 200 and

your not supposed to use maya pproximations with mentalray its just waste of resources

[bravid2001]

Thanks Joojaa,

There is obviously plenty of learning I still need to do to get the hang of displacement maps. Can you recomend anything?

I set my displacement approx to fine view. This really helps and changes things. As for "dependent 0.5 with a raised maximum splits", I'm not sure how to find this information. The UV coverage is also still something I need to address. I'm going to digital tutors now to do some tutorials. 

Thanks again. 

[joojaa]

In the editor theres a checkbox called view dependent ( check it) it maes use fo your camera in dicing the mesh up this makes the data more  concentrated on what you see, so things closer get tesselated more.

The length value measuires how long chords to make the segments, when set to view dependent this value is number of on screen pixels. set it to 0.5 - 1.

Max sudbivision specifioes the max triangles available 5 is a lot but for a good fine which is aquite efficent for some things a vakue of 6 or 7 will make sure you get enough omph even when getting close.

[bravid2001]

Joojaa,

Any problem with taking the length value to under 0.5? In doing so,I'm getting better results.

[joojaa]

bigger memory consumption.