hello all,

I'm new to (but excitedl/sickly) working in VEX.

I have a very simple shader with a bump map that is being applied to Meta objects.

When I render (in the background or foreground with mantra) there is this rendering artifact.

You know how when you render, your image fills in little “box” increments (I don't know what it's called), until eventually you have an entire frame/image from these little separately calculated rendered boxes. Well these little boxes are leaving strange “grid patterns” on the edges of each box. So in the end, my render looks like graph paper. Each box leaves a funny outline.

This only happens when I use the bump map.
Even when my bump map settings are extremely low,
and the “Displace Bound” (on the obj level) is set high,
this effect still shows up.

Here is a link to an image that this happened with:

http://www.emsh.calarts.edu/~jim/bogus.1.jpg [emsh.calarts.edu]

This happens in Houdini version 7.0.348 for windows (and a previous version of 7 as well).

anyone run into this one before?
any help/insight would be greatly appreciated.

Thanks

Jim Ellis

Hmn, no idea, I don't think I've ever seen this before. It doesn't really look like displacement cracking. Is this a scene that you can post (or one like it maybe)?

I've had issues like that in the past - nothing recently though. One thing you could do is try to increase your grid cache - set it to something like 32000.

It does seem like a bug of some sort though.

Can I suggest you output an IFD and zip it up and allow us and Side Effects support to download it and trace it down?

Have you tried varying the bucket size using the mantra -b option? See if they still line up with the buckets.
Also, try using an md window rather than an ip window, if I remember correctly an md window renders in lines of buckets rather than spirals, it might be interesting to see if this effects the artifact.

Hey All,

thanks for the replies!
I certainly appreciate them!

As I said… I am new to VEX, and I think my problem could be pilot error….
but I'm not sure yet.
How embarrassing… but we all have to start somewhere/sometime I suppose.

I think it could be the actual bump maps repetition is forming strange tiling issues on the edges that just happen to harmonize with the “bucket size”.
The relative relation of the tiling to the bucket size made me initially think there could possibly be a problem with rendering bump maps on Meta objects with Mantra. This (or course) I now doubt.

I'm just now getting back to the scene to trouble-shoot it on this recently devised notion.

I'll type back and let you know what I find.
Thanks again for your help given to this VEX newbie.

all my best

Jim