Hi All,
I'm completely stuck trying to fix a large-world viewport jittering issue. My goal is to convert a 32-bit USD (point3f) to a 64-bit USD (point3d).

I'm using an Attribute Cast SOP to convert my P attribute to 64-bit float.

However, when I export using the USD Export SOP, the saved file is always point3f (32-bit).

How can I force Houdini to save my 64-bit points SOP data to disk and load it in stage context?

Is this a bug in Houdini 20.0.445, or am I doing something wrong in my workflow?

Limitation of USD maybe.

Thanks for the reply. I'm not sure if it's a limitation of the USD format itself.

My scene's transformation values are huge—we're millions of units away from the origin. For example, a typical transform is:

X: ~9.89e+06 (9,890,000)
Y: ~4.22e+05 (422,000)
Z: ~1.0e+07 (10,000,000)

Because my exported point3f data is only 32-bit, the precision loss is catastrophic. I'm seeing all the classic symptoms: weird artifacts, jiggling vertices, and completely broken, flickering shadows.

For now, I've found that using a Match Size LOP on the environment and Character can work as a temporary workaround by moving the caches to grid, but we can't do this for a whole line of shots.

If we can't force Houdini to export 64-bit P, is there any other way to solve this precision issue in the stage context without matchsize lop?

Some more info here regardimg USD and 64bit. https://forum.aousd.org/t/double-support-in-geometry-data/808/14 [forum.aousd.org]

But yes, only solution I know of is to move the part that needs to be rendered to the center and scale down the scene. Redshift have a nice feature that can help in cases like this, Render in Camera Space. But you are using Karma I suppose.

Edit:

From the documentation https://www.sidefx.com/docs/houdini//solaris/kug/motionblur.html [www.sidefx.com]

"Note

In USD, points is a single-precision attribute. Transforms (such as xformOps) are double-precision."