If the object is not on screen, I don't draw it. When extremely high above everything, the draw count really drops as well as the pixels drawn per frame. I'm also cropping as well to keep the total drawn-pixel counts as low as possible. Here are 3 screenshots showing what I mean, with Windows Task Manager in the background:
This shows a case of about 5600 draws per frame. This is because the very far buildings are 6x2 pixels, almost nothing. Here, I'm getting about 50 frames per second, not all that bad, but it results in the scene being jerky rather than smooth.
With tons of height, way, way above everything, I could be running at about 140 fps with this scene.
This is a case where the pixels drawn per frame is extremely high (due to all the snow from the snowstorm - 9 layers that cover the full 1024x768 display area) with relatively few draws per frame. When I had my GeForce 7600 GT, I was getting 100% CPU usage on one core and about 60% GPU usage despite about 35 to 40 fps. With my new GTX 460, it's no longer a problem as I can get about 100 fps like this.
In all 3 cases, note the two fields of data on my debug panel on the bottom left corner. The top of these is how many draws are being made each frame. Multiply this by 60 to get draws per second. The other is for the number of pixels drawn each frame. Again, multiply this by 60 to get how many pixels are drawn every second. The third screenshot has over a billion pixels drawn per frame. The first isn't even close to a half billion and does much worse.
I do intend on using SDL, though originally only for vsync and fullscreen. I was only wondering why AlphaBlend was causing so much CPU usage with just drawing.