How to render object on cylinder

[L2zz]

Hi!
I'm going to implement an application that allows an object (Andy) to rotate along the side of the cylinder.
I'd like some advice on this. Specifically, the conditions and questions are as follows.

Overview of the target App

Conditions

Cylinder

• Rendering using geospatial API
• Scalable radius and height

Andy

• Rendering on the side of the cylinder
• Rotatable along the side of the cylinder

Questions

1. How to scale the radius or height of the cylinder?
As far as I know, ArModelNode is the only one that supports geospatial API.
The ArModelNode can be scaled through a scaleToUnits, but this changes the overall size.
What I want is to change the radius or height separately according to the user's request.
So, I wonder how to specify the scales for the x, y, and z axes individually for the model.

2. How to rotate Andy along the side of the cylinder?
I think directly rendering the Andy model along the side of the cylinder model seems difficult.
So I divide this process into two steps.

1. Rendering Andy as away as the radius from the centerline of the cylinder.
2. Rotate Andy relative to the centerline of the cylinder.

For the above steps, I would like to ask for a way to render and rotate the model
relative to the axis outside the object (here, the centerline of the cylinder).

Thanks very much for supporting this wonderful library 👍.

[ThomasGorisse]

Hi,

Very interesting and clear question (even if you should better put it in the Discussion section).

What I would suggest is having an ArModelNode with Plane placement that displays a cylinder coming from a glb for now.
For now because it will soon (v1.0.0) be easier and more efficient to use a Cylinder Geometry (It will look like this: https://gist.github.com/ThomasGorisse/7e07681e6aae794982ced3bc61af7f8d)
But if it is well defined inside Blender, it's not much more consuming to have it coming from a glTF.

You can then change its dimensions using the

sceneview-android/sceneview/src/main/java/io/github/sceneview/node/Node.kt

Line 184 in b7341cc

var scale: Scale = scale

Keep z at 1.0f and adjust the radius with scale.x and the height with scale.y

For the Andy part, depending on if you want your Cylinder to rotate with him or not, you can simply add it has a child or as sub-child ModelNode:

sceneview-android/sceneview/src/main/java/io/github/sceneview/node/NodeParent.kt

Line 44 in b7341cc

fun addChild(child: Node): Node {

If you want it to be independent from the Cylinder, add the Cylinder as a child of your ArNode instead of loading the glb at the ArNode level.

For the rotation part, all you have to do is to put it at a certain distance using

sceneview-android/sceneview/src/main/java/io/github/sceneview/node/Node.kt

Line 143 in b7341cc

var position: Position = position

from the pivot ArNode and then rotate the ArNode.

You can also have a look at the

sceneview-android/sceneview/src/main/java/io/github/sceneview/node/Node.kt

Line 734 in b7341cc

fun lookAt(

:-) function for controlling what is Andy looking at during rotation.

Pay attention to the fact that depending on your ArNode.placementNode the rotation of your ArNode might be influenced by ARCore positionning.
For that reason you should have something like this:

ArModelNode
    > CylinderNode
    > PivotNode
       > AndyNode

[L2zz]

Thanks for your great help! And I'm sorry for using the wrong tab😂.

I have some more questions.

For the rotation part, all you have to do is to put it at a certain distance using

var position: Position = position

from the pivot ArNode and then rotate the ArNode.

The code seems to adjust the position by directly entering the value.
I didn't specify it above, but I want is rotating Andy through the user's gesture,
so the question is,
Q. How to fix the distance (here, radius) between the pivot and Andy during interaction with the user?

And I have a simple question about the relationship between the child and parent node.
Q. If I modify the scale of the parent, does the unit of the scale and position of the child are affected?

[L2zz]

I solved it in the way you suggested before. Thx!