Help How to build a goal net mesh to use with Obi?

[gabrimo]

Hello there, so I bought Obi Cloth last week and decided to implement a proper goal net with it.

It happens that my goal net model consists of 4 planes linked each other, which no planes on 2 of its sides and normals flipped inwards.

Considering that my explanation might not be so clear, here's a small clip showing the model, the black sides represent the backfaces:

https://imgur.com/a/wljGT2P

Not sure if this is what the documentation meant by non-manifold mesh, probably yes, because I can't assign this mesh to a standard cloth blueprint...

So considering that my model isn't compatible, how should I model a goal net then, because this is my only idea about such an object should be built...

[josemendez]

Hello there, so I bought Obi Cloth last week and decided to implement a proper goal net with it.

It happens that my goal net model consists of 4 planes linked each other, which no planes on 2 of its sides and normals flipped inwards.

Considering that my explanation might not be so clear, here's a small clip showing the model, the black sides represent the backfaces:

https://imgur.com/a/wljGT2P

Not sure if this is what the documentation meant by non-manifold mesh, probably yes, because I can't assign this mesh to a standard cloth blueprint...

So considering that my model isn't compatible, how should I model a goal net then, because this is my only idea about such an object should be built...

Hi!

Here each edge is shared by more than 2 faces, so this is by definition a non-manifold mesh and can't be simulated (as it can't exist in the real world).

There's no need to duplicate all faces and flip their normals. It's simpler and cheaper to just disable backface culling in your material, or use two materials (one for side A, one for side B, this is what the sample scenes in Obi do) or use a two-pass shader.

[gabrimo]

Hi!

Here each edge is shared by more than 2 faces, so this is by definition a non-manifold mesh and can't be simulated (as it can't exist in the real world).

There's no need to duplicate all faces and flip their normals. It's simpler and cheaper to just disable backface culling in your material, or use two materials (one for side A, one for side B, this is what the sample scenes in Obi do) or use a two-pass shader.

Ok but how shoud I compose the model? Maybe with 4 separated planes (one each side, one top and one back)?

This model is all connected, like a rectangle with 2 faces deleted. I read the definition of manifold and assumed that this model wouldn't work, but my doubt is how should I build the goal net to be functional with Obi.

If I build it with 4 planes, I imagine there would be issues regarding collisions in the edges for example..

[josemendez]

Ok but how shoud I compose the model? Maybe with 4 separated planes (one each side, one top and one back)?

This model is all connected, like a rectangle with 2 faces deleted. I read the definition of manifold and assumed that this model wouldn't work, but my doubt is how should I build the goal net to be functional with Obi.

If I build it with 4 planes, I imagine there would be issues regarding collisions in the edges for example..

The model is fine as-is in that regard. You can take a cube/prism, delete two faces, and it’s still 2-manifold, as it can be “unwrapped” onto a flat surface.

As long as the surface is orientable and there are no obvious non-manifold structures (isolated vertices, zero length edges, zero area faces, edges shared by more than two faces) it will work, so most meshes pose no problem. This post sums it up quite well: https://blender.stackexchange.com/questi...d-geometry

[gabrimo]

The model is fine as-is in that regard. You can take a cube/prism, delete two faces, and it’s still 2-manifold, as it can be “unwrapped” onto a flat surface.

As long as the surface is orientable and there are no obvious non-manifold structures (isolated vertices, zero length edges, zero area faces, edges shared by more than two faces) it will work, so most meshes pose no problem. This post sums it up quite well: https://blender.stackexchange.com/questi...d-geometry

Hmm, so I've missed something with this net model, because if Obi isn't recognizing it, means that my model has some of the mentioned flaws.

Anyway, thanks, I'll revise my model or try to build another one and test it again...

[josemendez]

Hmm, so I've missed something with this net model, because if Obi isn't recognizing it, means that my model has some of the mentioned flaws.

Anyway, thanks, I'll revise my model or try to build another one and test it again...

That sounds weird to me... what do you mean exactly when you say Obi doesnt recognize it? It should accept and recognize any mesh, both manifold and non-manifold, then show a warning message if it has detected any problems with it.

[gabrimo]

That sounds weird to me... what do you mean exactly when you say Obi doesnt recognize it? It should accept and recognize any mesh, both manifold and non-manifold, then show a warning message if it has detected any problems with it.

When I select the obi cloth blueprint and try to drag and drop the goal net fbx file in the "mesh" field, the forbidden icon appears. If I click on the circle button on the right side of the field to manually select the goal net, other 3D assets appear, but the goal net doesn't. So for some reason, it doesn't let me add my goal net model...

[josemendez]

When I select the obi cloth blueprint and try to drag and drop the goal net fbx file in the "mesh" field, the forbidden icon appears. If I click on the circle button on the right side of the field to manually select the goal net, other 3D assets appear, but the goal net doesn't. So for some reason, it doesn't let me add my goal net model...

Unity’s object fields don’t work that way. They filter only by *type*, a mesh field will accept *any* mesh. Obi doesn’t implement any custom UI field behavior.

Are you sure you’re dragging a mesh, and not a prefab? When you import a FBX file, it may contain a transform hierarchy, one or more meshes, animation clips, cameras, materials, etc. You must drag just the mesh, not the entire thing.

[gabrimo]

Unity’s object fields don’t work that way. They filter only by *type*, a mesh field will accept *any* mesh. Obi doesn’t implement any custom UI field behavior.

Are you sure you’re dragging a mesh, and not a prefab? When you import a FBX file, it may contain a transform hierarchy, one or more meshes, animation clips, cameras, materials, etc. You must drag just the mesh, not the entire thing.

Oh, you're right, I've watched the tutorials, even so I managed to miss this detail, now it worked. Many thanks, I'm feeling the dumbest person on earth right now...

[josemendez]

Oh, you're right, I've watched the tutorials, even so I managed to miss this detail, now it worked. Many thanks, I'm feeling the dumbest person on earth right now...

No worries! we all make mistakes . Something sounded off in the way you described the problem, that’s why I dug deeper!

Let me know if you need any help.

Cheers,