I'm attaching two images with screenshots. I will use them to explain how the CenterOffsetY property works.
I will start with that the CoverFlow control tries to simulate a 3D world and as every 3D world it has Ox, Oy and Oz axes. As we want to project this 3D world on the screen all these axes has their projections on the screen. The CoverFlow itself has its Ox and Oy and we will put them in the middle of the CoverFlow control area. Now we can define what CenterOffsetX and CenterOffsetY are:
- CenterOffsetX is the difference between the projection of the Oy axis and the line that divides the CoverFlow control vertically into two equal pieces
- CenterOffsetY is the difference between the projection of the Ox axis and the line that divides the CoverFlow control horizontally into two equal pieces.
Let's demonstrate this with two examples.
On the first image, we simplified the situation by putting the Camera on the Oz axis. This makes the whole Oxz plane to be projected in a line, because the camera is on this plane, too. The difference between this line (the yellow line on the image) and the middle of the CoverFlow control (the red line on the image) is the CenterOffsetY property. In this case it is -40.
In the second example, the camera is lifted a bit and the images look different. Now their bottoms don't stay on one line. This is because the Oxz plane is no more projected as a single line, but the bottoms of the images are still on this plane. Now it is harder to find the projection of the Ox axis and to find its distance to the middle of the CoverFlow control. Now the projection of the Ox is the line that crosses trough all the points with X and Z positions 0. In our scenario, this points are all the middle-bottom points of the images except the selected one (it has ZPosition -500). Hence, the yellow line should be trough the red point and parallel to the red line. The CenterOffsetY is once again the difference between these two lines.
The situation is more simple with the CenterOffsetX property as the camera cannot be moved horizontally. In our examples the projection of the Oy axis and the middle of the CoverFlow control matches, so the CenterOffsetX equals 0.
Hope this information helps you understand how these properties work.
the Telerik team