TrailMesh - always starts from 0:0:0 (with PG example)

Bugs
1

Hello guys, I am not sure whether this is bug or not, but it definitely feels like an undesired behavior.

In following PG you can see that trail mesh starts at 0:0:0 which it should not because source mesh is at different location. After “one length of trail” it becomes ok, but first several frames look quite buggy at the first look.

What do you think about it ? Maybe I am missing something but it is workong well later on.

https://playground.babylonjs.com/#51I1DD

2

This artifact occurs because the world matrix of the sphere is not up to date the first time TrailMesh is doing its job.

You have to do:

sphere.computeWorldMatrix();

https://playground.babylonjs.com/#51I1DD#1

2 Likes
3

You can create the trail in the second frame, but your solution is better @Evgeni_Popov :smile:
https://playground.babylonjs.com/#51I1DD#2

2 Likes
4

Thanx guys, this computeWorldMatrix thingy works but really it is not obvious that it needs to be done (for someone who is not Jedi Master). But ok, logically the sphere is 0.0.0 until next frame so my mistake as usually :frowning:

But seemingly it doesnt work well with TransformNode as a genereator ? I am actually using TransformNode because I want just the trail - not really any visible generator - using transformNode it is still behaves as it did previously.

https://playground.babylonjs.com/#51I1DD#3

5

hi the alternative way
https://www.babylonjs-playground.com/#4AEW8L#16

https://www.babylonjs-playground.com/#CSZYEP#55

1 Like
6

TrailMesh takes an AbstractMesh as the generator: TransformNode is not a valid type for the constructor.

It does not raise an error because it’s javascript, but this code would not transpile with Typescript.

The easiest way is to hide the mesh with setEnabled():

https://playground.babylonjs.com/#51I1DD#4

Of course, don’t use a sphere as the generator mesh, it does generate way too many triangles for a hidden mesh!

7

Hello Evgeni, thanx very much !! I hesitated to use “real” mesh because I was afraid of another DrawCall for nothing. I didnt expect that it could work with disabled mesh. Now it is all clear, I will use some small disabled cube mesh as a generator.

Interesting is that it actually worked with transformNode (except that artifact at the beginning).

8

Nasimiasl: Thanx for nice inspiration … I am afraid that I am really far from that level of expertness though :slight_smile:

9

That’s because the generator passed in the constructor is not used for a lot of thing in the TrailMesh code, only 2 times:

let meshCenter = Vector3.Zero();
if (this._generator._boundingInfo) {
            meshCenter = this._generator._boundingInfo.boundingBox.centerWorld;
}

A TransformNode has no _boundingInfo property, so this code doesn’t retrieve meshCenter, but still the code does not crash (however, this is why there is an artifact when using a TransformNode in your PG - meshCenter == (0,0,0)).

and

        let wm = this._generator.getWorldMatrix();

This does work for a TransformNode.

It would be quite easy to make it work with a TransformNode…

Going to do a PR and we will see if it’s accepted :slight_smile:

2 Likes
10

It has been accepted Thanks a ton !!!

11

hmm i can help and make it easy for you
but that is not general for all mesh
i can help to make your special trail

*** notice that the secret of 60 fps optimization is make high quality fake

12

The PR should be up in 5 minutes

13

Thanx all of you guys, you are the best ! :)))

1 Like