[EMSUSD-9] Respect upAxis metadata

[pmolodo]

The upAxis setting in the metadata (https://graphics.pixar.com/usd/docs/api/group___usd_geom_up_axis__group.html) is currently ignored, meaning that any scene which has it's upAxis set as Z will be rotated.

Usdview respects this, and rotates the geometry accordingly, to always show the upAxis as "up".

The KitchenSet is a good example of an asset with upAxis=Z

[kxl-adsk]

@elrond79 How should this axis be respected? (FYI. @wtelford)

[pmolodo]

Basically, by just applying a top-level rotation; so that if opening a scene with "upAxis = Z", the z-axis (as defined in the USD) is rotated so that it displays as aligned with maya's up-Axis. This will make it appear "right side up" in maya's viewport. You can look at how usdview handles it for an example.

Of course, this is a potentially "dangerous" operation, as a point defined as being at (1,2,3) will no longer be displayed at those coordinates in maya... and it could potentially mess up alignment of various assets, if they're all brought with separate proxy shapes, and with offsets in the "original" z-up space. So it would definitely need to be controlled by an option of some sort.

But it would be a big convenience for some common test cases (ie, all the Pixar supplied ones, like KitchenSet).

[wtelford]

Hey @santosg87 , Can you link this to a Jira task if it exists?

[colaub]

Hi, any news about this issue?

[nicoluce]

Hi, we're in current need of this feature, as well as to properly handle the metersPerUnit metadata (#906). After some investigation on our end we concluded that although ideally we'd want to apply transformations to vertices, normals, etc. separately, a potential first iteration for Hydra mode could be:

• Add a layer under session layer that applies the necessary transformations at the top level of each Prim [1]
• Add a checkbox in the UI for the user to control this option

The reason for applying this under a layer is to have them bundled together in one place. Code-wise I believe (some) necessary steps for this would be:

1. Add "AP_upAxis" and "AP_metersPerUnit" attributes to MayaUsdProxyShapeBase
2. Modify ProxyAccessor::collectAccessorItems() to handle stage level metadata items
3. Add getUpAxis() and getMetersPerUnit() to MayaUsdProxyShapeBase

As to the actual layer and transformation code, I'm unsure about the specific place to place that logic.

Does this sound ok to you? Should the export operation handle these properties properly as well to consider this complete? If you already have plans for this feature internally, any estimate on it?

[1] Applying a scale and rotation at Prim is not ideal given that child nodes coordinate space isn't at scale but that is not a problem if you only care about rendering, which for 1st iteration should be fine from our point of view.

[sshklifov]

Hello, I see that this issue has been references multiple times. It will be useful for V-Ray for Maya as well. I can prepare a branch with a solution similar to the one suggested by @pmolodo . In addition to it, older scenes will have to use the old behavior. This can be achieved with the checkbox that @nicoluce mentioned.

Will you be willing to merge this change if I prepare a branch for it? Or is there a problem with this solution?