Terrain Generator trims mesh if exceeding 65k vertices

Help & Support
1

Hello guys!

I’ve tried this terrain generator: https://developer.playcanvas.com/en/tutorials/terrain-generation/
But it seems like it starts trimming the mesh once subdivisions go > 255 (number of vertices > 65k)

This doc claims it should be possible to generate meshes with >65k of vertices / indices: https://developer.playcanvas.com/en/api/pc.Mesh.html#setIndices

But seems like it’s not the case. Is it a bug or smth?

2

When you say ‘trim’, do you mean the collision mesh or the visible render?

3

The visible render also!

I didn’t try to reproduce it on original project, but in my project using this script the trimming happens. Should I provide a public example?

4

There is a limit on the number of vertices in a number of older devices that don’t support 32-bit index buffers. I am not sure though that’s the issue in your case.

I’ve tried the default terrain example with 300 subdivisions and it seems to work quite alright:

image
image1458×1314 388 KB

5

@Leonidas thank you for quick look!
I was trying my project in desktop environment, so it’s not mobile issue…
I’ll try reproducing this issue in original tutorial project then.

1 Like
6

@Leonidas @yaustar the trimming happens in tutorial project as well
to notice it you just need to set width / depth to 10, max height to 1
and then compare 250 subdivs vs 400, for example.

Cloned tutorial project with 400 subdivs:
https://playcanvas.com/project/773098/

Seems like something is wrong with pc.createMesh

7

You are right, but what’s interesting is that the collision mesh works. Here is me standing mid air because the collision mesh was fully generated:

image
image1631×1226 409 KB

@mvaligursky do you any idea what may the issue here?

8

Yeah, the collision is generated with 0.5 * subdiv, so it will not be trimmed until subdiv = 512

9

pc.CreateMesh only supports 16bit index buffers:

We need to port it to use new mesh api which does not have that limitation.

Alternatively, you can do one of these:

  • use Mesh API directly when generating terrain, instead of createMesh function. Note that as mentioned, some old mobile devices do not support 32bit index buffer

  • generates terrain in multiple patches, where each path does not go over 65535 vertices

4 Likes
10

@mvaligursky Thank you!

@yaustar @Leonidas Replacing

var mesh = pc.createMesh (this.app.graphicsDevice, vertexData.positions,
{
    normals: vertexData.normals,
    uvs: vertexData.uvs,
    indices: vertexData.indices
});

with this:

var mesh = new pc.Mesh (this.app.graphicsDevice);
mesh.setPositions (vertexData.positions);
mesh.setNormals (vertexData.normals);
mesh.setIndices (vertexData.indices);
mesh.setUvs (0, vertexData.uvs);
mesh.update ();

basically solves this issue

3 Likes
11

Thanks for sharing @underlight! Good to know.

1 Like
12

Added ticket to track the need to update the tutorial: https://github.com/playcanvas/developer.playcanvas.com/issues/247

Many thanks @underlight!

1 Like