Different displacement result in Preview & MPlay

[ganzo]

Hi Guys,

Up to this moment the forum has been extremely helpful in finding answers and information, but now I found the need to ask for help since I have not found any answers on the forum. So hi all and hope this is a good first post.

I am creating a material and have been using ipr/render view to watch my progress using a teapot. My material is pretty simple...I am just using several noise nodes to drive color mixes and displacements. IPR/render view does get buggy on auto update after I change any displacement parameter, but it is just a matter of stopping and restarting it. I also have a properties node with displacement bounds added so I dont run into the cut off displacement artifact.

To keep this short, I was happy with my result and ran a normal mantra render to see the results and I thought they would not be off by much, but the render is totally off...displacement and color wise. Can anyone point me in the right direction on this issue? Using the "scene view" camera on the render view yields the results I want, but switching to my render camera in renderview or running MPlay screws up the render ... really lost on this. Hope you guys can lend me a hand...thanks!

- Alex

[lukeiamyourfather]

What does your displacement shader network look like?

[ganzo]

This is a simplified version with just the displacement part. Removed nodes that just contribute to color for simplicity. Like I said...displacement part is fairly straightforward. But is my error really on my shopvop? Is the displacement calculated differently in the render view?

[lukeiamyourfather]

I don't see a transform node in there, in which case the displacements are in camera space (not object/world space). So if the resolution and/or camera view changes it will change the displacements. Try dropping down a transform node and change the space to object space. Then at the end of the network transform it back to camera space before plugging into the output.

[ganzo]

Thanks for the reply, I initially did think that it was a space issue and had just added a transform before the noise, but did not add one at the end of the network. Now is this before the displacement output for both normal and position?

Edited April 21, 2011 by ganzo

[lukeiamyourfather]

It might be the same issue, not sure how your color is derived.

[ganzo]

Been trying to fix this, but still not getting acceptable results. Should I space convert position inputs to noise nodes as well as the inputs to the displace along normal node? ...also adding transform to cam space before displacement output on the normal yields no results, but if I add to displace position the result is completely wrong. I'm adding a sample scene with the network if anyone can take a quick look at it. Not really sure what I'm doing wrong..

Thanks!

displacement.hip

[ganzo]

I'm noticing that this is more of a shading topic than a rendering one...so If any of the mods could move this to shading...thanks!

[ganzo]

Well I managed to get this problem solved...really simple actually. Like lukeiamyourfather had suggested I indeed was missing a transform before my noise nodes to switch from camera space to object space. Putting another transform before "displacement output" node to bring back to camera space was not really needed. This alone,however, did not solve the problem of my renderview and mantra render being very different. In the end it was the "object space" toggle inside the "displace along normal" node that put both views in sync. There is a really tiny color discrepancy between both views but nothing to be worried about.

My mud shader now works like I want. For those interested it is a procedural mud shader with moss growth control. Nothing fancy, but I like the results.