Holes in the ground

[Dad72]

HI,

 

Does anyone have an idea of ​​how we create Holes in the ground by removing faces?

 

This can be used to create of enter underground cave, tunnel, gallery ...

 

Thanks

[Temechon]

Did you try CSG ? http://www.babylonjs.com/?CSG

Maybe with a big box and a tube it can work...

[RaananW]

CSG is a feature I always forget exists. But it is an amazing feature :-) Thanks for reminding it is there!

[jerome]

GSG or poly2tri

 

with the first one, you create fist a mesh, then you remove parts with another mesh

with the second one, you create a 2D complex polygon, which can have holes, then it creates the relative plane (with holes)

[Dad72]

I'll try with CSG can be a good solution.

 

Thanks

[Dad72]

Its not working as I would like.

 

What I want is to create a hole by removing the face of the field. Then I place a 3d model to the hole.

 

exemple:

 

[jerome]

What happens if you use CSG with a cylinder to dig a hole in your terrain ?

[Dad72]

CSG is not suitable. I would just by clicking on the faces of the terrain that removes polygons to form a hole. The irregularity of the hole is not imortante, a model 3d will hide it.

[jahow]

The pick() function of a scene gives you the id of the face picked. You are then able to use this to remove the three corresponding indices in the indice array of the meshes. This way you effectively remove the picked face (but not its vertices).

 

Example here (based on the decals PG): http://www.babylonjs-playground.com/#1BAPRM#19

 

Is that what you're looking for?

[Dad72]

yes, that's exactly what I was looking for. thank you Jahow

[jahow]

good luck on your editor!

[Dad72]

Thank you Jahow. 

 

I have one last question. if I want to add a radius to remove more faces, what are the best ways to do it ? thanks.

[jahow]

That's a bit more complex. I think I would check all vertices close to the picked point, and remove those that are under a certain distance (= hole radius). For each vertex removed, I would have to delete the associated faces in the indices array.

 

Not sure if that would work, I'll try to do it in the PG...

[Dad72]

thank you Jahow  for your help.

[jahow]

I managed to get it working: http://www.babylonjs-playground.com/#8OMYN#4

 

But:

1/ I do not remove the vertices, only the faces. So after a while the mes might need to be cleaned (ie remove vertices that are not used)

2/ There should be some possible optimization by looking only into submeshes vertices, instead of all the vertices of the mesh (since pickInfo gives you a submeshID)

 

Good luck

[Dad72]

Cool, is perfect. thank you very much Jahow for help 

[Dad72]

Hi,

 

Still thank you for helping me Jahow for this function. I would go the other way to close the holes. is it possible ?
 
I have this function to create the holes. I would like to create a function: addFaces () that recreate the missing faces.

        var removeFaces = function (pickInfo, radius)	{				var mesh = pickInfo.pickedMesh,			faceID = pickInfo.faceId,			indices_array = mesh.getIndices(),			positions_array = mesh.getVerticesData(BABYLON.VertexBuffer.PositionKind),			vertices_toremove = [],			pickpoint = pickInfo.pickedPoint,			current_v = new BABYLON.Vector3.Zero(),			worldmatrix = mesh.getWorldMatrix(),			index,			safety = 1000;					for(var i=0; i<positions_array.length/3; i++)		{			current_v.x = positions_array[i*3];			current_v.y = positions_array[i*3+1];			current_v.z = positions_array[i*3+2];			current_v = BABYLON.Vector3.TransformCoordinates(current_v, worldmatrix);								if(BABYLON.Vector3.Distance(pickpoint, current_v) < radius) 			{				vertices_toremove.push(i);			}		}					for(var i = 0; i < vertices_toremove.length; i++)		{			index = indices_array.indexOf(vertices_toremove[i]);			while(index != -1)			{				indices_array.splice(index - index%3, 3);				break;			}		}					mesh.setIndices(indices_array);    };    var addFaces = function (pickInfo, radius)    {	????    };

 
Thank you for the help.

[jahow]

Hey dad72, sorry for not responding earlier.

 

Adding the faces back is not trivial, unless we save the indices of the faces we've removed earlier. In this case it's just a matter of putting back those faces in the mesh. But it may not be suitable for every use, since the "removed faces" info can become quite big if you remove a lot of stuff, and must be saved with the mesh otherwise it won't be possible to add its faces back.

 

Herre is an example: http://www.babylonjs-playground.com/#8OMYN#5

The first time you click, faces will be removed. If you click back somewhere on the mesh, the faces around the click will be restored. It still has one problem: since we removed the faces from the mesh, nothing happens if we click in the hole...

 

Here are a few suggestions for you:

- Maybe setting vertices alpha (transparency) to zero would be easier than remove them, because we wouldn't have to actually modify the mesh and clicks in 'holes' would still be detected ; the big drawback is that the mesh would then be classified as "transparent", which may pose other problems

- If you plan to use this exclusively for a heightmap, a simpler & more efficient method can probably be found because all your vertices and faces are on a grid and it is easier to know what to remove/add

- Another method: for each mesh than can have hole in it, create an "inverse mesh" which will hold all the vertices & faces that have been removed from the main mesh. This mesh can be invisible but will still detects when we click on it.

[jahow]

Another try: http://www.babylonjs-playground.com/#8OMYN#9

 

This time I'm switching the face direction, meaning that the faces will become invisible if backface culling is activated. They can easily be switched back afterwards  Also the geometry is not changed at all.

 

You have "l'embarras du choix"!

[Dad72]

I like the latter. Thank you Jahow, but the question I ask myself is: Is that if I hide the faces, a character can pass through the holes. The collision is still activate in the holes or no? I wish that a character can pass through this mesh where the holes are.

 

Thank you again Jahow.

[jahow]

Well, I know almost nothing about collisions in BJS so I can't really say for sure... But I guess you'd have to actually remove faces like I did in the first example I gave you.

[Dad72]

I just think of a solution. From the editor last solution to hide the faces and record them in a .dat. And when one is in game I take all the faces hidden this .dat file and I delete as your first solution. I think it will work like this.

 

I think this time everything is ok.

 

Big thanks Jahow

[Dad72]

Arf, my solution does not work in case the user want to close the hole in the future. it is necessary that I remove the collision on the faces hidden only.

 

So I think Deltakosh is able to answer that :

Can we disable collisions on some faces of a mesh. If so, how? Thank you very much

[joshcamas]

Do I spy a hobbit hole?

[Dad72]

What do you mean by: "hobbit hole" ?