[Forge] Low FPS on 1.15+ with Forge

[TheFinkie]

Description of Issue

I have noticed significantly lower FPS when Forge is installed. This doesn't happen on 1.14.4, only 1.15-1.16. The issue is most prominent in areas with lots of leaves (e.g. modified jungle). I believe it is a compatibility issue between Optifine and Forge, because Forge alone doesn't have problems and Optifine alone doesn't either.

I have included screenshots to illustrate the problem. In these pictures, I am using BSL shaders, but note that the problem is always present regardless of which shader I use (including Shaders Off). No settings have been changed between the screenshots except as noted.

Steps to Reproduce

1. Install Forge.
2. Add Optifine to mod folder.
3. Create world (for reproduction purposes, a Modified Jungle buffet world is best because of its dense leaves).
4. Look at an area where lots of leaves are in view.
5. Wait a few minutes for the world to fully load.
6. Observe the FPS.

OptiFine Version

I have tried:

• OptiFine 1.15.2 HD U G1 pre30
• OptiFine 1.16.1 HD U G2
• OptiFine 1.16.2 HD U G3

I can confirm that there is NO problem in:

• OptiFine 1.14.4 HD U F5

Installation Method

Explained under Steps to Reproduce

Fabric/Forge Version

I have tried:

• forge-1.15.2-31.2.0
• forge-1.15.2-31.2.36
• forge-1.16.1-32.0.108
• forge-1.16.2-33.0.20

I can confirm that there is NO problem in:

• forge-1.14.4-28.2.0

Other Installed Mods

NO OTHER MODS besides Forge (and Optifine).

Log Files/Crash Reports

I don't think this section is relevent, but please let me know if you need anything.

F3 Debug Screenshot

Fig.1: Minecraft 1.14.4 with Optifine – runs perfectly.

Fig. 2: Minecraft 1.14.4 with Optifine & Forge – runs perfectly.

Fig. 3: Minecraft 1.15.2 with Optifine – runs perfectly.

Fig. 4: Minecraft 1.15.2 with Optifine & Forge – huge FPS drop.

Prior Testing

I have done extensive testing, and the results are as written in this report.

Additional Information

If you need any more information, please let me know. As far as I can tell, the problem is with Optifine, but if you think otherwise, please tell me what else could be causing this.

[sp614x]

Tested Modified Jungle world in 1.16.5 with OptiFine G6 and Forge 36.0.0 + OptiFine G6:

OptiFine standalone:

Forge + OptiFine:

Please test with G6 for 1.16.x and 1.15.2, it has additional Forge compatibility fixes.

[TheFinkie]

It seems you have proven this to not be an Optifine bug, but for the record, I am still having the issue using the exact versions you used in your screenshots:

I guess it's fair to close the issue, but there is definitely something wrong here that only appeared after 1.14.

[sp614x]

Does this also happen without shaders?

[sp614x]

Seeing that the GPU is NVidia with Max-Q Design, this may be due to thermal throttling or the GPU running in power saving mode. You can check in the graphics control panel if the GPU can be switched to Performance mode or something similar.