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View Full Version : Modo's thinking addressing poly geometry? [pics]/[bug]


onlooker
10-04-2004, 04:52 AM
I started this by trying to use basic poly tools as I would in Maya, and I think the geometry is handled weird by the edges, and points.

The grey backing is Maya, blue is Modo.

With a simple 4 corner 4 point poly plane I split it down the middle corner to corner in both applications, and added a point in the center of the split. #4 identifies the point in all pictures. I then pulled the point up in Y axis to create a pyramid, and here is where I noticed some strange behavior in Modo.

(BTW, I did this test a few times to check)

You see where I pointed at #3 in all pictures. Modo did not create the pyramid I expected. One side of the geometry was favored, and lifted with the edge, while the other stayed flat with the plane which left an artifact which I point at #2. an invisible, or non existent edge on the same parallel with the plane. You can see it in the bottom right picture, and in the one to it's upper left corner. Also in that corner in the #2 reference it appears to be that an extrusion was made when pulled up in the Y axis. Clearly visible is a poly artifact that I think should not be present in these circumstances.

To get the best look at this I suggest a quick recreation, and look at it with the faces selected, and not selected in modo, and rotate around the geometry to take a closer look.

If some of you could do this simple test I would appreciate it.

If this is an nvidia bug, or something that I am not aware my apologies.

leonard-davi
10-04-2004, 05:28 AM
some times i have the same problem .. i modeling and boOOMMM ! oh my god i lost one edge .... it's comom but i press tab and ( /) to go non wired view and look .. and nothing hapens ,, maybe it's a realy litle bug i use nvidia card to :\ if some one have solution post here .. in my case dont afect in nothing but all time this become sux !!


-sorry about english ;\

hugs ...

shwepsi
10-04-2004, 01:14 PM
I have no problems... Made a 4 by 4 poly using Pen tool then select 2 verts (on opposite corner) and ctrl-L (spit poly)... Then edge split resulting edge to a corner vertex and again ctrl-L to the remaining unsplited poly... move the center vertex Y

shwepsi
10-04-2004, 01:19 PM
I have no problems... Made a 4 by 4 poly using Pen tool then select 2 verts (on opposite corner) and ctrl-L (spit poly)... Then edge split resulting edge to a corner vertex and again ctrl-L to the remaining unsplited poly... move the center vertex Y

onlooker
10-04-2004, 06:28 PM
I have no problems... Made a 4 by 4 poly using Pen tool then select 2 verts (on opposite corner) and ctrl-L (spit poly)... Then edge split resulting edge to a corner vertex and again ctrl-L to the remaining unsplited poly... move the center vertex Y
I'm not sure if I read what you said correctly, but there is only one split. It looks like 2 triangles butted up against each other. With one point added in the middle of the split.

MattClary
10-04-2004, 07:40 PM
If this diagram reflects what you are doing, with the X marking a point, by lifting it, you are making the polys non-planar, so I'm not surprised you are seeing odd behavior.

onlooker
10-04-2004, 09:43 PM
That is the correct diagram, but in Maya it does what I would expect of it in the real world. Imagine if it were stretched cloth fastened to a square. If I were to sew an elastic string across the middle between two corners, and pull the elastic string up at it's center - the opposite side that crosses where the elastic string was not present if it were pulled evenly and tightly at the point it would still make a pyramid shape.

Don't get me wrong I'm not trying to criticize Modo - I like it too much. I'm giving these details, and input so they can be fixed. I think it's just a young app, and we need to point these little things out to help it grow properly. Little stuff like this I expected to see early on.

c-g
10-04-2004, 10:15 PM
Maya seems to be using triangles internally instead of keeping the geometry as you really see it. Modo is keeping it as a quad.

Cronholio
10-05-2004, 12:26 AM
If this diagram reflects what you are doing, with the X marking a point, by lifting it, you are making the polys non-planar, so I'm not surprised you are seeing odd behavior. Polygons of 4 sides or more should not be required to have coplanar points. Infact looking at the images you can see that the 4th point doesn't move. This looks like a bug to me. Maya is hadling the geometry correctly.

onlooker
10-05-2004, 12:40 AM
Oops.. Double Post.. :rolleyes: :rolleyes:

onlooker
10-05-2004, 12:41 AM
What I see is Maya "chose", and maybe calculated the natural fold. It also didn't leave an unrequested polygon from the ground plane up the Y axis.
Maya developers learned a lot about geometry, and UV's from it's nurbs beginnings.

Although I am unfamiliar with the particulars of UV Mapping, and coordinates I think analyzing, and rethinking this could help solve some (If there are any) UV bugs that exist in modo. I don't think UV's would/could respect that geometry.

c-g
10-05-2004, 01:20 AM
Polygons of 4 sides or more should not be required to have coplanar points. Infact looking at the images you can see that the 4th point doesn't move. This looks like a bug to me. Maya is hadling the geometry correctly.
It is just as easy to say Modo is handeling it correctly since it isn't subdividing the nonplanar polygon on it's own.

Cronholio
10-05-2004, 01:39 AM
Nope, actually that's wrong. Somehow the point order on his geometry got screwed up. I just had someone try to reproduce this and they couldn't, Modo was handling the geometry the same way that Maya (and every other application I've used) handles the geometry. Onlooker, maybe you could tell us step by step how you created that?

onlooker
10-05-2004, 02:37 AM
Well an interesting thing has happened. Today is a whole new ball game. I went through to record my exact steps, and today the geometry is acting correctly.

What I do notice that appears different is that the normals seem to be pointing up, and outward, and yesterday I remember them pointing down, and inward, but here were the steps anyways:

The steps are simple. I made 4 points clockwise using the pen tool. I then selected point 1, and 3, then hit Control-L (split poly) hit spacebar once into "Edges" mode select your new edge, and hit C (edge slice) at 50.0% with Check Boxes = Split at the middle , and = Split Polygons turned off (unchecked). Then hit space twice into "vertices" mode, selecting the new vertex, and hit "t" Element move tool, and press W, and grabbed the handle for the Y axis, and pulled up in Y.

That was it. Maybe I should have restarted the app yesterday before trying to recreate it the second, and 3rd time.
If I would have it probably would not have reproduced it both times. That is all I can think of that is different today.

We'll I'm glad it's corrected nevertheless. :D :applause:

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