This is weird...
Se the render to Main window, if it isn't already. Then, when you're getting lag, look in the bottom right corner of the window. There will be two speeds represented, the FPS, and the VPS. Are they both at 60 with a 100% next to them?
Se the render to Main window, if it isn't already. Then, when you're getting lag, look in the bottom right corner of the window. There will be two speeds represented, the FPS, and the VPS. Are they both at 60 with a 100% next to them?