How to unwarp the foveated frames outside alvr?

[Jia-WeiFang]

Hi,
Since I want to calculate the objective metrics between the foveated-wrapped images and unwarped images, I save both the original eye texture and the warped texture on the server side.
(The reason why I didn't just save frames from the client is that the HMD hardware can not afford to save frames in runtime, the workload is too heavy; the app would shut down. In addition, the HMD will do some cropping before displaying the frames, so I can not directly use the screen recording either.)

Thus, I wonder how can I do the unwarping function offline?
I have created an OpenGL project and followed the render pipeline in the client source code, and use "CalculateFoveationVars" function to calculate the foveated parameters, the fragment shader in alvr/client_core/cpp/ffr.cpp, and the vertex shader "QUAD_2D_VERTEX_SHADER", but I can not get the correct unwarped results.

Can I have the original test OpenGL project of doing the warping and unwarping work, or can you tell me how to do this offline?

Thanks a lot!
Really appreciate your help!

Jia-Wei

[zmerp]

The current FFR algorithm was written by @sctanf, maybe she can help. if you want to record the stream output I highly recommend to just not using FFR.

[sctanf]

@Jia-WeiFang color=texture(tex0, uv); would skip the decompressing entirely

[Jia-WeiFang]

Dear @sctanf,
May I ask what are the meanings of your non-linear and linear functions in desmos ?

Thanks a lot for your help!
Jia-Wei

[sctanf]

@Jia-WeiFang the non-linear sections have increasing compression as it reaches the edge, the linear section is uncompressed

[Jia-WeiFang]

Dear @sctanf,
Thanks for your reply!

Does your non-linear function follow some math theory?
Or it is just your heuristic method?

Can you briefly explain your design concept~?

Thank you a lot!!!

Jia-Wei

[sctanf]

@Jia-WeiFang the functions are created to have an adjustable average slope and avoid discontinuity but there is not much other consideration in its design, other than some pixel alignment in the final shader