Same issue as many games have. Have you ever played Counter-strike, RB6 or any game where you can use a smoke grenade? Walk in the middle of the smoke, and you'll notice your FPS goes down to 5-12. Its when a sprite is super large and takes up a lot of space on the screen for some reason this slows it down...
Sorry this isn't exactly an explanation of why, or how to fix it...however I've hit the same exact problem with a game I'm working on now. I have a dragon that breathes fire, when the dragon breathes fire (made up of sprites) away from the camera, therein making them smaller, it runs a solid 60 FPS. However, if the flames are blown at the camera, making them huge when they are nearing the hither of the view fustrum the game slows down to almost 2 FPS.
Weirdest thing, no idea why, but I remember this being the case with soo many professional games so you're not the only one running into this problem.
If I find anything out I'll let ya know...
Sorry this isn't exactly an explanation of why, or how to fix it...however I've hit the same exact problem with a game I'm working on now. I have a dragon that breathes fire, when the dragon breathes fire (made up of sprites) away from the camera, therein making them smaller, it runs a solid 60 FPS. However, if the flames are blown at the camera, making them huge when they are nearing the hither of the view fustrum the game slows down to almost 2 FPS.
Weirdest thing, no idea why, but I remember this being the case with soo many professional games so you're not the only one running into this problem.
If I find anything out I'll let ya know...