Wpf Animation performance drops suddenly

I have a simple fade in animation on a large Rectangle inside a ScrollViewer and I notice a significant drop in performance when I increase my windows size past a certain size.

1. resolution: 1650x1256 - still feels snappy and fluent (framerate between 50 and 60)
2. resolution: 1820x1256 - stutters and is pretty much unusable开发者_如何学运维 (framerate between 7 and 15)

What surprises me is that there doesn't seem to be a linear decline in performance but a rather sudden drop.

Also using Wpf Performance Tool does NOT show any software rendering and indeed my CPU doesn't seem to be doing much when the animation runs.

I would like to understand the cause of this, any hints would be appreciated.

Another possibility is that you are running out of dedicated video memory at that resolution, so DirectX is transferring a lot of data back and forth between video memory and main system memory on every frame.

Is there any way you can try a different graphics card, or one with more RAM, to see if the problem changes?

Also, does your GPU have a way to configure how much system RAM is reserved as video memory? Some do.

My guess is that you are running out of GPU memory at that point, so DirectX is dropping back to software rendering.

When you say a "viewport", do you mean a ViewPort3D, or do you mean a Viewbox? If it is a Viewport3D, is the animation really needing the 3D processing? If not, you could use 2D and use a transform to simulate 3D the way Flash applications have to do.