Hello. I've just tried SnowRain plugin with AGS 3.4.1. The resolution is 1920*1080, 32-bit color and game speed is 60. I had 35 FPS with OpenGL, 47 FPS with Direct3D and 60 FPS with software renderer. How is that possible? Software renderer is better than Direct3D? My graphics card is Geforce GTX 1050 TI 4GB.
This plugin is not truly suitable for Direct3D and OpenGL. We did some changes to the engine to let it run the plugin with these drivers too, but it uses a workaround. My guess is that may be slower, and the higher game resolution is the more noticeable effect it has.
Have you done any fps tests without plugin?