Read prim attribute error!

I want to get into graph action to rotate the blades of a helicopter that I made in blender , so I started with the " basic node" tutorial about how to rotate a cube, however, the “read prim attribute” has a red colour error, I checked the forum and I saw there was a solution which is “creating a new node from the list”,but even though there was no “empty” error, the cube did not budge at all ! am I missing something here ? I added the cube as target and set to “xform rotatexyz” !

Hi @Massinissa. Can you share an example USD stage showing what you’re trying?

I am following a tutorial " introduction to omniverse action graph" a very basic one " a simple method to rotate a cube ,but there is that “empty error” that occurred all the time !

prim error|690x387

the " read prim attribute " is always in error when I drag the “cube” or when I select it from the list node, it seems the " add target" does not work at all with it…the node seems empty and the cube does not rotate

and if I click on the three dots it became " red erro" again !

Hi @Massinissa. I think you’re talking about this tutorial? Introduction to Omniverse Action Graph | NVIDIA On-Demand

The error message when the ReadPrimAttribute node is created is a known issue and it is being fixed. I was able to just continue with the the tutorial and get it to work anyways. In order for the clear the error message, the node needs to be executed and it can be a little unintuitive to get this node to execute. In this is screenshot:

When I click the play button, OnTick executes WritePrimAttribute via connection A. ActionGraph then follows the graph backwards (see arrow B) and executes ReadPrimAttribute in order to fulfill the WritePrimAttribute.Value.

NOTE: Decompose/Compose nodes have been replaced with “Break 3-Vector” and “Make 3-Vector” respectively.

Hope that helps!

yes… the error disappeared when I click play, however the cube does not rotate !!

at last, I figured it out , in “constant double” you have to change the "input’ value 0 to whatever you like so the cube starts to rotate ! it was not mentioned in the tutorial because it started by default !

thanks for your help !

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