Hello!

Does anyone know how to fix a problem in my shading? I have this rocks made procedurally, and also texture procedurally. When I add bump or displacement, I start getting some black artifacts. They disappear or increase as I put lower or higher values of strength in the bumping or displacement. How can I ger rid of those? Are they caused because the normals are intersecting with the geo?

there is an image attached

I can't seem to download the file, but what you're describing sounds like a displacement bounds issue. You may just need to increase the bounds in order to displace the geometry properly.

Hey! thanks so much for your response. Your answer definitely pointed me into a great direction, the problem is I couldnt make it work. I reloaded my image in the previous post so you can see the trouble im having.

I dont know if the problem is that I built my own shader and Im probably missing some attributes or maybe im connecting sth wrong because I added the “displacement bound” and used this advice I saw in another post:

“A good rule of thumb for initial settings for displacement bounds should be approximately two thirds of the absolute displacement value in the displacement shader(2/3*displacement_value)”
http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&p=13343&sid=a06612def187090f13783bb559eff27f [sidefx.com]

I also added the “true displacement” parameter because I saw it was mentioned on several other posts, but Im still not sure of why it isnt working yet.

Im attaching an image so you can see the setup im using for displacement. In this case im only using Bump because the displacement makes the black artifacts more noticeable. The scale amount im using is of 1 so my displacement bounds is 0.66 (using the formula above), but ive tried other values and still the artifacts remain.

I would appreciate your help
Also if you have some comments about the render, or general look, i will be very happy to hear them

It could a spot where there's just a sharp crease, which could cause a self intersection after displacement – you could try smoothing the geometry in that area to see if it helps. You could also try smoothing the normals too possibly.

Did you also add the displacement bound parameter to your geometry? On your geo node at object level, you need to also add in the displacement bound parameter, and it should be set the same as in your shader. It will be added into the “shading” sub tab. As well, under the “dicing” tab you might want to use “ray predicting”.

When displacing it is also important that the geometry has proper normals and a rest attribute.

Here is a really cool thread, with a great screenshot showing how to stack displacements ( You will need the re-dice parameter).

Hope this helps, in truth, displacements are amazing in Houdini, but I do find that it always takes a little bit of noodeling and I am always learning new things. It would be great to have everything covering displacements in one clear concise place.

BTW - your noise is outputting a vector and it should be a float to go into amount.(1D noise, or a luminance). Throw a fit range after that noise and play with the lower values in the top two rows. Play around on a phere or something first so the render times are more responsive.

As a trick I sometimes pipe in the luminance node into the shader output with everything disconected to see what my noise looks like fast. You can also create noise in cops and pipe that through.

Hi again! thanks for your responses, they have taught me a lot; but Im afraid I cant still make it work. I tried adding the “displacement bound” parameter in the geometry at obj level, with “ray predicting”; and I also post-computed normals and gave the geo a rest attritbute.

Or is there sth im missing?
Also… sl0throp, you forgot to post the link of the stacking displacement tutorial, i would appreciate if you post it please.

Thanks for all your help!
Im very grateful

EDIT - Hey..looking at your node graph again..you have nothing piped into the
nN attribute of the displace along normal. Pull up a displacement globals, pipe n into a normalize and then pipe that into the nN(normalized normals) on your Displace along normals


Have you tried upping the shading quality on the dicing tab to 2 or 3?

http://forums.odforce.net/topic/6517-unofficial-displacement-rendering-challenge/ [forums.odforce.net]