I do upload my work at Pixiv but i did not get a warning yet, maybe they did not noticed my account yet!
What i do is to upload my 3d art as a series but i hide the genitals with lens flare or a change the camera view on the first image and unhide the genitals on the following series.
Not sure if this censorship cheat is really effective only time will tell.
In my case, the mail from Pixiv looked like this:
Dear user,
Thank you for using our service.
We have found that the work(s) you posted was not concealed appropriately.
The work(s) below requires modification in accordance with the guidelines:
・The work is visible through solid-color concealment.
・The work with extremely fine mosaic grain size relative to the vertical and horizontal size of the illustration.
・The work that has not been concealed up to its outline.
Other than those listed above, if the genitals are not concealed or exposed due to insufficient concealment,the work(s) needs to be revised.
■ Work(s) in question(for example)
https://www.pixiv.net/artworks/103422740
We have made it possible for you to reupload your work after it has been revised, so please make the necessary edits.
■ Reupload page
https://www.pixiv.net/upload.php?mode=re_upload&illust_id=103422740
Please also check for any other works that violate the terms of use or guidelines, and if so, please register for pixiv Premium to reupload them or delete them.
In any case, we ask that you reply to us within 7 days through below link.
https://www.pixiv.net/support?type=15&mode=inquiry&service=pixiv
If we confirm there is no reply or no measures were taken, your account may be suspended without notice in advance.
■ pixiv Terms of Use
https://policies.pixiv.net/
■ pixiv Guidelines
https://www.pixiv.net/terms/?page=guideline
Examples of expressions that require the use of mosaics/pixelation
・Genitals or areas reminiscent of genitals
・The union or joining of the genitals and the insertion of foreign objects
・The union or joining of anuses and the insertion of foreign objects
・Areas that are unnecessarily detailed due to being exposed by cuts, lacerations, etc.
Other users have been similarly warned. We ask you to use our service in compliance with the Terms of Use and Guidelines.
Due to the recent increase in Internet surveillance, the Internet Hotline Center (ICH) entrusted by the Japanese National Police Agency, may request us to take down work(s).
We recommend that you cover up as much as possible by referring to adult magazines sold at bookstores.
Thank you for your understanding.
Regards,
pixiv
After I had revised the pictures and reported this to Pixiv, I received the following mail:
Dear user,
Thank you for using our service.
We have verified that you have taken the necessary measures regarding the work(s) you were previously warned about.
Please note that in the event we observe similar behavior in the future, we might suspend your account without notice.
Please go through all your work(s) again.
Even if you have not been warned about a specific work, we ask that you still take the appropriate action.
Please use pixiv in accordance with the Terms of Use and Guidelines.
■ Terms of Use
https://policies.pixiv.net/
■ Guidelines
https://www.pixiv.net/terms/?page=guideline
Regards,
pixiv
From experience with Deviantart I know that the cleanup there took months.
Only there you were simply banned and the account deleted.
I have been posting on Pixiv since 2019 and have never been warned. Therefore I was very surprised when I received this mail. I thought that if a newbie publishes something that does not comply with the rules, that he will be written to promptly. They must have gotten one on the lid themselves.
But it does not matter. I am now the best friend of Pixiv. 
Now I don't want to write anything about it here either. After all, we are here on MadBob his side. The soon has no more place to publish something.
Sorry John.
looks like they’re about to pump her for information 
