[NEEDS INPUT] Sporadic fps drops with post processing enabled [ Edited ]

[puzzlezaddict]

Product: The Sims 4
Platform:PC
Which language are you playing the game in? English
How often does the bug occur? Every time (100%)
What is your current game version number? 1.61.15.1020
What expansions, game packs, and stuff packs do you have installed? everything from Seasons forward
Steps: How can we find the bug ourselves? Compare the same location and viewing angle with post processing enabled and disabled, while in live mode.
What happens when the bug occurs? Fps drops by a significant margin (over 10%) when viewing certain locations with post processing enabled, but other locations are unaffected.
What do you expect to see? that post processing has a relatively consistent effect (hopefully minimal) across all locations
Have you installed any customization with the game, e.g. Custom Content or Mods? Never used.
Did this issue appear after a specific patch or change you made to your system? Neutral/Not Sure 

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(These screenshots and fps measurements are taken from Windows, but I saw the same pattern in macOS Mojave, on an iMac 18,3, 7600K, Radeon Pro 580.)

In most examples, enabling post processing seems to have a negligible effect on framerates.  I checked three locations in Sulani, three in Britechester, and one in each of the other worlds I own, with either no difference or a margin less than 5%.  While I understand that post processing in most games will cost some performance, that doesn't seem to be the case in Sims 4.

However, in Ward Park (Del Sol Valley) and outside the Oasis Springs bar, fps dropped more than 10%.  I don't know whether the buildings in the background made any difference, since I haven't tested every single lot, but the only locations where I saw any fps drop had a backdrop of buildings.  I doubt the issue is the amount of detail per se, as Sulani had no fps drops at all.

Viewing angles were as close as I could make them; other than post processing, settings were on ultra.  I used windowed fullscreen with a resolution of 2560x1440.

Ward Park, post processing enabled, 120 fps:

Ward Park, post processing off, 138 fps:

Oasis Springs outside bar, post processing on, 139 fps:

Oasis Springs outside bar, post processing off, 156 fps:

Specs: 9700k, RTX 2070, game installed on 860 Evo.

[puzzlezaddict]

This is on the same system, hardware and driver, as before.

I found another illustrative example of the fps drop, this time on one of the Sulani islands.  Mua Pel'am starts out dirty and almost barren but can be restored to look like the rest of Sulani through hard work and persistence, or a couple of convenient cheats (enabled by TwistedMexi's AllCheats mod).  I checked three viewing angles on Mua at all levels of restoration, both with post processing off, and only noticed a significant fps drop with one of them.

Unrestored, post processing on, fps = 170:

Partially restored, post processing on, fps was 160.

Fully restored, post processing on, fps = 147:

At this saved camera state, with post processing off, fps dropped from a high of 179 unrestored to 166 restored, a much smaller difference.

At the other two camera positions I checked, both with similar distances and viewing angles, fps ranged from 166 to 179, with post processing not creating a reliable fps drop, and restoration accounting for less than a 5% fps drop.