hi again!! i have both a bump and displace map applied to my model.. the bump map seems to be interfering with the displace map and resulting in fuzzy, speckly black rendering artifacts.. they dont occur when either one is turned off but when both on together they occur.

any ideas?

cheers again..

don't know off the top of my head, any chance you could post a simple .hip
somewhere so I can have a look at it?

Sounds like bad normals.

You obviously have Displace Bounds set correctly for the object receiving the displacements.

Do the texture maps themselves have sharp contrast areas? You know pixels with little gradation between value changes where you have jumps between the pixels?

What shaders are you using? Are they the defaults or are they your own? If they are your own, are you displacing and bumping the surface by their normals?

hey.. the bump shader is my own, but the displace is the generic displace… my bump is bumping by surface normal… (is there another way?)

It might be aliasing, with both bumps on you could be effectively doubling the frequency of your bump and that might push it up over the sampling frequency.
Try turning up the sampling in the render or reduceing the frequency of the bump or displacement. If it is this you might need to concider implimenting some anti-aliasing in the shaders.

simon - cheers, i`ll try playing with that… what seems especially strange though isthat i get the artifacts even if the displace is set to 0 bu stillt applied to the surface.

Yup that is a little weird. I assume by what you are saying that if you completely remove it it works fine but setting it to 0 it messes up. I can't think of any reason why that would be the case.