PolygonMeshBuilder and Meshbuilder not working

Questions
1

Morning all,

I’m experimenting building meshes programmatically and whilst the playground examples from the documentation seem straight forward I am finding that even with small changes I am not getting the behavior I expect.

For example:

The linked playground is based on a number of examples from the documentation but whilst the BABYLON.MeshBuilder.CreateLines method works and the lines appear as I would expect. Trying to turn this into a face and/or then an extrude using either BABYLON.PolygonMeshBuilder or BABYLON.MeshBuilder.ExtrudePolygon doesn’t seem to do anything. In the playground nothing renders and when running directly in the browser using a local webserver the screen just turns white which suggests I’m not implementing correctly.

I’m sure this is quite straight forward but I’m not sure what to try next as I think I’m using the syntax from the examples correctly?

Best,
Sy

2

Hi,

I think that’s because your shape is not in the XZ plane. The y coordinate must be equal to 0
I made this playground to explain you with a depth of 100

Here’s the link to the docs that explains

Good luck :wink:

1 Like
3

Thanks for this - so you can only extrude in the Y direction? That seems pretty limiting? Is there any way to specify a path direction that is not Y with the polygon on any plane?

For example, on mesh might be drawn on XZ and extruded in Y but another might be drawn on XY and extruded in Z?

Thanks for you assistance with this.

best,
Sy

4

This PG shows difference between CreateLines, PolygonMeshBuilder and Create and Extrude Polygon

Yes there is

However you can only use the cap parameter successfully with a convex polygon

You could use ExtrudePolygon and then rotate the mesh to match the direction you want. You can use

to match the rotation needed.

1 Like
5

Hello,

Thanks for the feedback. I believe I understand the concept now and it appears that this is more a limitation in how the meshes are constructed as opposed to anything else.

I believe the following PG will demonstrate my understanding better.

In this case a simple square is drawn on each plane, XY, YZ and XZ and then closed. These squares plot as expected.

For each square a subsequent path is defined which is essentially normal to the plane the square is drawn on.

If I extrude each shape along each path my expected behavior would be a final render of 3 cubes which are coincident about the origin (0,0,0) This is not the behavior produced. However, from your explanations I can see why it is rendering the way it is in the PG.

The final geometry I wish to produce involves a lot of shapes being drawn on different planes, extruded normal to those plans and booleaned to each other. Unless there is someway to achieve the behavior I describe I think it will be too complicated drawing everything on XY and then translating/rotating to suit. In this instance I may be better drawing what I need in a CAD package and then using STL exports instead. The downside to this is that my final geometry will be “dead” as opposed to parametric if I could have drawn it live in Babylon.

Thanks.

6

It is about how you choose the points relative to the origin

However with concave shapes there would be a problem with the end planes or caps

2 Likes
7

Hello @insidef1 just checking in, was your question answered? :slight_smile: