how to export EXRs with mipmaps?

[Pawel29518055g8ov]

we would like to be able to export EXR textures with mipmaps

currently, we have to process all painter outputs using oiiotool (txmake) and rewrite the EXRs in a more rendering-friendly format. 

as far as I can tell there is no way to control the format directly from substance painter export. Is there a flag (or API call) that we could use to change how the exrs are written?

thank you.

[Cyril Dellenbach]

Hello @Pawel29518055g8ov,

Thank you for the message.

Unfortunately, I am afraid I'll need more information to give you a proper help. What do you mean by "more rendering-friendly format" ? What is your end-goal with the EXRs?

Keep me updated.

[Pawel29518055g8ov]

Hi Cyril,

I'm sorry for not explaining it properly in the first place. Lemme elaborate 🙂

EXR file can store multiple sizes of the same image as different levels of mipmaps. Currently, we can use ocio tools to convert them after they are exported from substance painter but it would be very convenient to have them written with mipmaps directly. Besides the mipmapping there might be some other differences in how the EXR files are written to allow quick access of portions of the textures only. Standard EXRs have to be read whole by the renderer and that generates a lot of network traffic and slows down the rendering. Optimised for rendering EXRs are an order of magnitude faster and generate hardly any network traffic. To be honest I'm not entirely sure what the exact differences (besides the mipmap levels) are in the way they are written. I would need to research it more.

here is a relevant article about the conversion process that we use:
https://openimageio.readthedocs.io/en/latest/maketx.html

thank you.

[Cyril Dellenbach]

Thank you very much for the clarification!

After a quick discussion with the team, I can tell you it isn't possible to change how the .EXR are written and unfortunately this isn't something we are currently interested in. I am afraid we can't help you to smooth your current workflow.

Best regards,