(For more resources on Flash, see here.)

# Ordering the buildings

The buildings are not well placed on the map. They overlap with each other in a very strange way. That is because we are now viewing the 3D isometric world in 2D screen with wrong ordering.

When we view the 3D perspective in the following way, the closer objects should block the view of the objects behind. The buildings in the preceding image do not obey this real-world rule and cause some strange overlapping. We are going to solve this problem in the next section.

## Ordering the movie clips in Flash

In Flash, every movie clip has its own depth. The depth is called z-order or the z-index of the movie clip. A movie clip with bigger z-order number is higher and covers the others with lower z-order when overlapping. By swapping their z-order, we can rearrange the movie clips on how they overlap and create the correct ordering of isometric buildings.

## Determining an object’s location and view

According to our tile-based isometric map, the object that locates in larger number of the x and y axis is in front of the object that locates in smaller number of the x and y axis. We can thus compare the isometric x and y coordinate to determine which object is in front.

There is a special case when all shapes of the buildings occupy square shapes. In this situation, the order of the movie clip’s z order can be easily determined by comparing their y position.