Forums Technical Discussion Copernicus ROP then File read error Transform not invertible

Copernicus ROP then File read error Transform not invertible

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NNNenov
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Hello,

I am trying to "cache" a stage of my copernicus workflow.

I created a ROP node and wrote an .exr
I then created a file node to read back in the exr and use it in my later COP workflow.

The issue is that as soon as I create a blend node to mix it with other nodes in my workflow, I get this error
"Warning Transform not invertible"


I tried setting colorspace conversion to raw in my ROP image output node, I also tried other output formats, setting Data Size to different settings and ticking raw, same for reading the file back in with the file node, I also tried using an OCIO transform node with various settings, no matter what I do, I cant read back in my file and use it with a blend node.
I also tried image/texture sampling it, project layer, I couldnt figure it out, is it a bug?

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Transform_not_invertable.png (170.8 KB)

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NNNenov
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Joined: Feb. 2016
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I have the solution from sidefx team Midgardsormr via discord:

From a developer: 
Yeah, Blend COP works in world space, considering the transforms of the background and foreground

That error basically means that the projection matrix of the foreground onto the background plane is not invertible, so we can't resample it

One degenerate case where this can happen is if the two images are perpendicular (e.g. one is looking down the Z axis while the other is looking down the X axis)

If you don't care for the world-space matching, you should use Match Camera to get the foreground to have the same transform as the background before feeding them into Blend



I cant say I understand how transforms work in COP context, in this situation.

Attachments:
fixTransform.png (57.6 KB)

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