bump map artefacts

[rray]

I'm often getting these line artefacts when using bumpmaps, with all materials. The lines get wider as I increase the bump spacing value.

They're always running exactly along the mesh edges,
is this something known/worth reporting/there a fix?

MR, Bump_Map shader

Cheers

[Mathaeus]

I sow this before, last time on portrait of Iggy Pop on XSI Base, created by someone from SI team, I think. So most like it's already known issue. Don't know fix, anyway.

[ActionArt]

That's a strange one, I haven't seen that before. What happens when you reduce your sample spacing to around .001 or less?

[rray]

Thanks for the replies.
Action Art, then the seams becomes more and more faint but the look of the bump changes too, larger structures like the stones become invisible.

Maybe I'll be possible to get an other menral ray bump shader working

[angelous4x]

i've also had this problem, one way to got around it was messing around the mesh splitting setting in the optimize mental ray options.

let us know how it goes.

[rray]

That indeed works! Thanks angelous!

[angelous4x]

I am glad it did.

but a heads up. sometimes you have to find a good setting. some times it just moves it around. so take a look around your mesh.

cheers

[Kzin]

are you using uvtiles?
have these tiles a hard border between the parts which are painted and which not? if yes, try to minimize the color contrast for these lines.
best is to reload these tiles on your model in your 3d painting app and look if these lines are also visible here. then you can do a fast overpaint to eleminate them.

[rray]

Kzin - I'm using "texture instancing" for this object, it turns out MR is splitting up the mesh into pieces for rendering and the bump_map shader doesn't interpolate well between those pieces. I wonder something like that is necessary anmore today, or if that's something that was developed when typical RAM was around 128MB.

angelous4x will look out for that! I used a value of 10 for the mesh splitting factor, and considering turning the splitting off altogether by setting the XSI_DISABLE_MESH_SPLITTING environment var (found this tip in the mailing list).

[Kzin]

Kzin - I'm using "texture instancing" for this object, it turns out MR is splitting up the mesh into pieces for rendering and the bump_map shader doesn't interpolate well between those pieces. I wonder something like that is necessary anmore today, or if that's something that was developed when typical RAM was around 128MB.

if the texture instancer does is right by default then it looks like a bug of mr. will ask if this a known thing.

[gustavoeb]

Nice tip rray ive never used that after going 64bits anyways, never went into such an issu with bump mapping either thoguh

[Pancho]

What did you set for the mesh splitting environemt variable? ON, 1, ....?

[rray]

@Gustavo: I wonder why I didn't ever notice it ... one of the things that once they become ovious they can't ever be overlooked again.

@Pancho: I did set it to 1, but I noticed doing so can easily double render times (as does using high values for the mesh splitting factor)

It looks like the bump shader needs a little fix. Would be nice to have access to the sources of some of these basic factory shaders.