[v9] Texture gets overwritten instead of swapped out on prop change.

[roelkok]

I'm using v9 and I ran into an issue were a texture that I was using kept being overwritten.

Let's say I have 3 textures A, B, and C and a component with a MeshBasicMaterial. When I pass texture A to the map prop of the material, then later on B and finally C, my component seems to render the updates fine. However when I pass texture A again, I see no update.

function MyComponent({ myTexture }) {
  return <mesh>
    <planeGeometry args={[2, 2]} />
    <meshBasicMaterial map={myTexture} />
  </mesh>
}

I realized that the material kept using the same texture (A) but that the contents of it kept being overwritten with the other textures. So when using texture A again after C no change was visible because its contents were overwritten by C.

I created a pull request that doesn't copy a new texture into an existing one on a instance on prop change by checking the UUID. It fixes the issue in my case, but not sure if this is the right approach.

[drcmda]

thanks! this is really interesting! you are 100% right that this is bugged or wrong behaviour, just nobody stepped into it yet.

this is what happens currently:

• map={a}, because map is originally NULL fiber will mutate material.map = a 👍
• map={b}, which in fiber translates to material.map.copy(b) because both target & value constructors now match and have .copy(), the texture gets overwritten with B, so A is destroyed 😬
• map={a}, which is material.map(a), it copies itself and will still show texture B 🫣

the problem is that it has destroyed the A texture, the app can never go back to that

the correct behaviour would imo be,

• map = a because map is NULL 👍
• map = b, bc it originally used to be NULL, we must assume an external object that we shouldn't mutate directly 👍
• map = a, bc it originally used to be NULL, same as above 👍

it would now show texture A

we can probably detect if something was originally NULL ... we do something similar in the diffProps function, fiber maintains a collection of default/original values. this could tap into that and check.

[RektTillNoon]

nice catch!

[roelkok]

I can confirm the fix in rc5 works for me.