USD Exporter Error: metersPerUnit does not match retrieved type float #90519

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Dan McLaughlin · 2021-08-08T15:44:07+02:00

Dan McLaughlin commented

2021-08-08 15:44:07 +02:00

System Information
Operating system: Window 10
Graphics card: Titan

Blender Version
Broken: 2.93

Short description of error
Verified the error on importing into two application, Unreal 5 and Nvidia Metaverse View, both of which report the same problem that metersPerUnit has a requested type of double, but the retrieved value is float.

Exact steps for others to reproduce the error
Export a USDC file, settings don't seem to matter (and shouldn't)
Import into another program

**System Information** Operating system: Window 10 Graphics card: Titan **Blender Version** Broken: 2.93 **Short description of error** Verified the error on importing into two application, Unreal 5 and Nvidia Metaverse View, both of which report the same problem that metersPerUnit has a requested type of double, but the retrieved value is float. **Exact steps for others to reproduce the error** Export a USDC file, settings don't seem to matter (and shouldn't) Import into another program

Dan McLaughlin commented

2021-08-08 15:44:07 +02:00

Added subscriber: @DrMc

Germano Cavalcante commented

2021-08-09 14:55:56 +02:00

Added subscribers: @makowalski, @mano-wii

Germano Cavalcante commented

2021-08-09 14:55:56 +02:00

I couldn't investigate the issue as I don't have Unreal 5 or Nvidia Metaverse View to test.

@makowalski, if I'm not mistaken, you worked on that exporter, right?
Any idea what this metersPerUnit warning is?

I couldn't investigate the issue as I don't have `Unreal 5` or `Nvidia Metaverse View` to test. @makowalski, if I'm not mistaken, you worked on that exporter, right? Any idea what this `metersPerUnit` warning is?

Dan McLaughlin commented

2021-08-09 15:06:43 +02:00

I would guess any application that imports USD would notice it, basically the Blender file is saying one thing but doing another, it's probably as simple as changing the variable type actually being exported.

I believe meters per unit it nothing more than ordinary scene scale. E.g. the data is stored with dimensionless units, and metersPerUnit tells you how to interpret it. Unreal has an option to set it.

I would guess any application that imports USD would notice it, basically the Blender file is saying one thing but doing another, it's probably as simple as changing the variable type actually being exported. I believe meters per unit it nothing more than ordinary scene scale. E.g. the data is stored with dimensionless units, and metersPerUnit tells you how to interpret it. Unreal has an option to set it. ![image.png](https://archive.blender.org/developer/F10275181/image.png)

Michael Kowalski commented

2021-08-10 16:10:32 +02:00

@mano-wii My apologies for the delayed reply. I actually worked on the USD importer, not the exporter. However, looking at the code, I confirmed that @DrMc is correct: there is a small error in the code that is setting the metersPerUnit value to a float instead of the expected double. It should be a very easy fix in the Blender USD exporter code.

@mano-wii My apologies for the delayed reply. I actually worked on the USD importer, not the exporter. However, looking at the code, I confirmed that @DrMc is correct: there is a small error in the code that is setting the `metersPerUnit` value to a `float` instead of the expected `double`. It should be a very easy fix in the Blender USD exporter code.

Michael Kowalski commented

2021-08-10 16:44:21 +02:00

Indeed, it seems that a simple cast like the following (in usd_capi_export.cc, line 104) fixes the warning:

usd_stage->SetMetadata(pxr::UsdGeomTokens->metersPerUnit,
                       static_cast<double>(scene->unit.scale_length));

Indeed, it seems that a simple cast like the following (in usd_capi_export.cc, line 104) fixes the warning: ``` usd_stage->SetMetadata(pxr::UsdGeomTokens->metersPerUnit, static_cast<double>(scene->unit.scale_length)); ```

Dan McLaughlin commented

2021-08-10 17:23:53 +02:00

Just a note @makowalski that it's actually an error not a warning, for both applications it fails to load the Blender export due to this.

Germano Cavalcante commented

2021-08-10 21:28:47 +02:00

Added subscriber: @dr.sybren

Germano Cavalcante commented

2021-08-10 21:28:47 +02:00

In #90519#1204632, @makowalski wrote:
Indeed, it seems that a simple cast like the following (in usd_capi_export.cc, line 104) fixes the warning:
usd_stage->SetMetadata(pxr::UsdGeomTokens->metersPerUnit,
                       static_cast<double>(scene->unit.scale_length));

It seems like a simple and safe change.
I wouldn't mind committing, but the code was introduced in ec62413f80.
So, @dr.sybren, would you mind taking a look?

> In #90519#1204632, @makowalski wrote: > Indeed, it seems that a simple cast like the following (in usd_capi_export.cc, line 104) fixes the warning: > > ``` > usd_stage->SetMetadata(pxr::UsdGeomTokens->metersPerUnit, > static_cast<double>(scene->unit.scale_length)); > ``` It seems like a simple and safe change. I wouldn't mind committing, but the code was introduced in ec62413f80. So, @dr.sybren, would you mind taking a look?

Sybren A. Stüvel commented

2021-08-11 10:16:28 +02:00

LGTM, @mano-wii by all means commit the fix.

blender-admin commented

2021-08-11 14:35:38 +02:00

This issue was referenced by bbcb60fb22

This issue was referenced by bbcb60fb22b375094836e4ab90569db1f73c42e3

Germano Cavalcante commented

2021-08-11 14:42:48 +02:00

Changed status from 'Needs Triage' to: 'Resolved'

Germano Cavalcante closed this issue

2021-08-11 14:42:48 +02:00

Germano Cavalcante self-assigned this 2021-08-11 14:42:48 +02:00

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USD Exporter Error: metersPerUnit does not match retrieved type float #90519