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View Full Version : In a mess with a mesh.



bcicio
06-26-2012, 01:25 PM
Hi guys. Pretty much still a novice here, not using LW very often and still on LW9.6. This SHOULD be simple. I'm trying to transform the mesh on the top side of a block (which I have give a decent amount of geometry) into a terrain by simply lassoing bunches of points here and there on the flat surface and moving them in the Y direction to alter elevation. I apply smoothing to the surface and it looks fine in Modeler -- but when I render the surface in Layout, the surface shows many small tears in it. I've tried subpatching the mesh (both types of subpatch) prior to moving the points, but a render still shows that the model has many small tears.

The reason I am attempting to transform the top surface of a block and not simply a flat plane is because I eventually need to cut the block and show a cross section of the terrain with underlying geology.

I assume subpatching is the correct course of action to take with this, but is there a subpatch setting I should be playing with somewhere that might affect how much the surface will be inclined to tear when stretched? (I'm obviously using defaults.) I just don't get why shared poly edges would separate (aka tear) at all when I am simply moving around their shared points in the y direction. Thanks for any pointers.

lwanmtr
06-26-2012, 01:31 PM
can you post a pic of what you get?

erikals
06-26-2012, 01:55 PM
maybe an old SSS render bug...?

see > http://forums.newtek.com/showpost.php?p=1182625&postcount=11

bcicio
06-26-2012, 02:12 PM
maybe an old SSS render bug...?

see > http://forums.newtek.com/showpost.php?p=1182625&postcount=11

Sorry, erikals. I'm just too much of a novice to see anything wrong in the detail of that model bug example.


can you post a pic of what you get?

I was hoping no one would ask that. I'm in the middle of a pc change-over and my LW is presently out of commission. Unfortunately, I didn't bother to save my previous renders to a file because I saw they had tears in them. Just figured I would inquire about this problem now that I had a moment to do so, but if the described tearing this is not a common problem amongst us novices I'll have to get back to this thread with examples as soon as I am up and running again. Probably should put this inquiry on hold for now. Thanks.

bcicio
06-26-2012, 02:28 PM
Another novice mistake I have made is not searching the forum for an answer before asking. I have found a few posts about similar surface tearing and am going to try a few of the suggestions when my new station is up and running. Thanks.

jeric_synergy
06-26-2012, 02:45 PM
The obvious suggestion is: if the polys are quads, your manipulations have made them non-planar.

But without samples, who knows? \:^*

lwanmtr
06-26-2012, 02:51 PM
but subd they shouldnt become non planar....unless they were frozen in modeler, then turning them into tris would fix it.

SplineGod
06-26-2012, 03:17 PM
This might be useful for creating your terrain:
http://www.youtube.com/watch?v=IJJ11YlRm6o&feature=plcp

bcicio
06-27-2012, 07:18 AM
The obvious suggestion is: if the polys are quads, your manipulations have made them non-planar.

Well, yes.. my polys were quads when it first happened. But then I tripled all of them and they still tore. I'm going to have to play with it more and post some samples. I'm also going to try going the displacement route using a graytone texture image that represents the topography I want for the surface rather than dragging around points and stretching polys.

Thanks for your weight map suggestion and tutorial, SplineGod, which I would also like to try as I have never worked with weight maps.

Sensei
06-27-2012, 07:42 AM
Object Properties > SubPatch Level, default is 3. So 3 * 3 = 9 polygons after freezing old sub-patch. Or 2^3 * 2^3 = 8 * 8 = 64 in Catmull-Clark Sub-Patch.. It's controlling how many polygons will be generated by sub-patches.


(I'm obviously using defaults.) I just don't get why shared poly edges would separate (aka tear) at all when I am simply moving around their shared points in the y direction. Thanks for any pointers.

Maybe it's simply not connected? Tried merging/welding points?
I hope so you didn't use Catmull-Clark Sub-Patch Edge Weighting.. ;)

Anyway, take screen-shot and attach in post.

jeric_synergy
06-27-2012, 08:22 AM
Or better SEND THE OBJECT. @^@

(Generally, isn't it obvious that screen shots and sample objects would get answers quicker and better here?)

erikals
06-27-2012, 10:51 AM
yup...

lwanmtr
06-27-2012, 01:31 PM
Yep, would be easier if we could see the object.

bcicio
06-27-2012, 01:36 PM
Should have lightwave back up and running tomorrow. Just waiting for a new license key from Newtek.

SplineGod
06-27-2012, 05:16 PM
Well, yes.. my polys were quads when it first happened. But then I tripled all of them and they still tore. I'm going to have to play with it more and post some samples. I'm also going to try going the displacement route using a graytone texture image that represents the topography I want for the surface rather than dragging around points and stretching polys.

Thanks for your weight map suggestion and tutorial, SplineGod, which I would also like to try as I have never worked with weight maps.

You can also paint weight maps. Most or all the modify tools have a weight fallloff as well. :)

erikals
06-27-2012, 05:21 PM
in this case, simply airbrushing the weightmaps would be the easiest...

but yes, for a more realistic result this method becomes limited.