Problem with components vertex positioning state

Questions
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1

Hi there,

I am building components that i want to reuse throughout my app in R3F. One of them is a fries (engl. plank?!?). To scale that fries i am using a method @PavelBoytchev provided to me (Scaling and positioning in Door Configurator - #8 by PavelBoytchev). I got it working in R3F but with that approach i cannot reuse the component. I thought about cloning the geometry but that did not work as expected…

Here is a codesandbox with my problem:
https://codesandbox.io/p/devbox/instanceuvtest-v75sqx

At first the width configuring works, but if i switch the component it does not work anymore.

Any advice would be great. I know that this method is overkill for this model, but it’s an abstraction for more complex models.

2

Hi there,

here is a try to make my problem more understandable.

What i have (https://codesandbox.io/p/devbox/instanceuvtest-v75sqx):

  • I got a component that displays a plank (custom glb file)
  • The plank can be scaled in it’s width (you can try that in the codesandbox)
  • The scaling is done by offsetting the vertices to the left and right
  • On first load that works as intended

The Problem:

  • When i switch the plank (switch from PlankA to Plank B in codesandbox) the scaling is suddently off
  • The remounting of the component somehow calculates wrong offsets

I think the problem is that i manipulate the vertices of the custom glb and next time the component mounts it does not know what the current values are anymore because they got re initialized when mounted.

What i tried:

  • I tried disposing the geometry so it always loads with the initial values
  • I tried cloning the geometry and do the manipulation only on the clone but i coulnd get it to work…
3

Working off of a cloned geometry sounds like the right approach. How did that manifest as not working?
Did you set geometry.attribute.position.needsUpdate after you finish editing the vertices?

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4

I use this approach to clone my glb in the component:

   const { scene } = useGLTF("./Fries.glb");
   const clone = useMemo(() => scene.clone(), [scene]);
   const { nodes } = useGraph(clone);

In my understanding, when i remount the component the scene graph gets cloned each time. But it doesnt work that way…

Did you set geometry.attribute.position.needsUpdate after you finish editing the vertices?

Yes i do in my applyTransformation function:

    const applyTransformation = (geometry, key) => {
    const widthOffsetStr = ((props.width - 1) / 2).toFixed(4);
    const widthOffset = parseFloat(widthOffsetStr);

    const position = geometry.getAttribute("position");
    const uv = geometry.getAttribute("uv");

    // Reset positions and UVs to original values
    position.array.set(originalAttributes.current[key].position);
    uv.array.set(originalAttributes.current[key].uv);

    let center = new THREE.Vector3(0, 0, 0);

    for (let i = 0; i < position.count; i++) {
      let z = position.getZ(i);
      position.setZ(i, z + widthOffset * Math.sign(z - center.z));
      uv.setY(i, uv.getY(i) * props.width);
    }

    position.needsUpdate = true;
    uv.needsUpdate = true;
  };
5

Okay i started from scratch and tried the cloning variant with references to the mesh and it worked. Here is the code: https://codesandbox.io/p/devbox/instanceuvtest-forked-p5zfnh

1 Like