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InstancedBufferGeometry.instanceCount incorrectly #19595

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sanddyl opened this issue Jun 9, 2020 · 7 comments
Closed
3 of 13 tasks

InstancedBufferGeometry.instanceCount incorrectly #19595

sanddyl opened this issue Jun 9, 2020 · 7 comments

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@sanddyl
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sanddyl commented Jun 9, 2020 •
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Description of the problem

When I changed InstancedBufferGeometry.instanceCount, I found that the _maxInstanceCount not changed. This will cause the InstancedBufferGeometry to display incorrectly.
W99N1@YTXLI_7BMX7TOGX51

Three.js version
  • Dev
  • r117
  • ...
Browser
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Hardware Requirements (graphics card, VR Device, ...)
@WestLangley
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@sanddyl Can you please provide a simple, live demo to show exactly what you did to cause the issue?

@sanddyl
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sanddyl commented Jun 9, 2020

@sanddyl Can you please provide a simple, live demo to show exactly what you did to cause the issue?

https://jsfiddle.net/s3xco4hk/95/

@WestLangley
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You are resizing the attribute buffer. That is not supported.

See https://threejs.org/docs/#manual/en/introduction/How-to-update-things.

/ping @Mugen87 for confirmation.

@sanddyl
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sanddyl commented Jun 9, 2020 •
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You are resizing the attribute buffer. That is not supported.

See https://threejs.org/docs/#manual/en/introduction/How-to-update-things.

/ping @Mugen87 for confirmation.

I quite agree,but when I need to modify maxInstanceCount, instanceCount can not achieve my purpose, even if this is rare. I mean, the instanceCount in version 117 is not equal to the maxInstancedCount in the previous version.

@sanddyl
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sanddyl commented Jun 9, 2020

You are resizing the attribute buffer. That is not supported.

See https://threejs.org/docs/#manual/en/introduction/How-to-update-things.

/ping @Mugen87 for confirmation.

Maybe both maxInstancedCount and instanceCount are required.

@Mugen87
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Mugen87 commented Jun 9, 2020 •
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Yes, buffers can't be resized. The idea is to create a sufficiently sized buffer and then control via drawRange or instanceCount (when using InstancedBufferGeometry) the rendering. This approach is demonstrated by webgl_buffergeometry_instancing.

Maybe both maxInstancedCount and instanceCount are required.

Nope. It does work by just using instanceCount. Check out how the updated fiddle controls the amount of rendered instances.

https://jsfiddle.net/brs1f5oa/

@sanddyl
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sanddyl commented Jun 9, 2020

Thanks a lot ! I will avoid such problems in the future.

@sanddyl sanddyl closed this as completed Jun 9, 2020
@WestLangley WestLangley mentioned this issue Jun 22, 2020
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13 tasks
lojjic added a commit to protectwise/troika that referenced this issue Jul 19, 2020
@lojjic
fix(troika-three-text): fix changing text length in ThreeJS r117+
a7ef945 
Fixes #69. This works around an issue introduced in Three r117 where a
given geometry uses the size of any InstancedBufferAttribute as a max
for `instanceCount`, and caches that for the lifetime of the geometry
even if the attribute is replaced with one of a different size.

It's unclear if this is a ThreeJS bug or a if our approach of "resizing"
by replacing the attribute is truly unsupported; the discussion in
mrdoob/three.js#19706 is ambiguous,
mrdoob/three.js#19595 implies it's not
allowed, and mrdoob/three.js#17418 implies it
should be allowed.
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@WestLangley @sanddyl @Mugen87