Gfx.ReadbackImage - Framrate drop to 15fsp

[francois85]

Im having some extreme slowness coming from Gfx.ReadbackImage. I was wondering if someone could run me through the what and why of this little vampire. From what i read on the web it passed info back to the CPU from the GPU. What kind of info and how do I reduce this call or the amount of data? It there something I’m doing to wrong that is causing this to be so slow?

Thanks in advance

[Amplify_Borba]

Hey there, could you please elaborate on the context of this situation?

Also, sharing Unity version and hardware specs would also be extremely useful in helping to understand the issue.

[francois85]

Sure, I have a shader that uses texture arrays to blend between the different texture indices. When I run the profile I seem to get some slowness on Gfx.ReadbackImage. See attachment. Im trying to investigate if there is something in my end that is causing this slowness.

-EDIT : its real time GI causing the slowness

[Amplify_Borba]

Thank you for the additional information, could you confirm if the issue is also present while using other similar shaders that take advantage of arrays?

[francois85]

Im sorry I dont have anything outside of amplify to compare it too at this time. Once you go amplify you never go back

[Amplify_Borba]

No problem, glad to know you have no plans of going back!

Feel free to let us know if you suspect that any performance hiccups might be related to our shaders, we'll be happy to help you debug the issue.