Landscape's initial task is to build the terrain and the four walls around it. The resulting scene graph is shown in Figure 26-4.
The number of
TexturedPlanes objects will vary depending on the height of the generated quads. Each
TexturedPlanes holds all the quads within a given height range, therefore allowing them to be assigned the same texture. This means that the program only has to create one texture per
TexturedPlanes object as opposed to one texture for each quad, a significant reduction in the number of objects.
Figure 26-4. Landscape's scene graph
The moving viewpoint hugs the landscape by utilizing Java 3D picking. I'll explain the details later, but it involves shooting a pick ray straight down underneath the viewpoint to hit a quad in the floor. The (x, y, z) coordinate of the intersection with the quad is obtained, and the y-value is used to set the y-axis position of the viewpoint.
TexturedPlanes are grouped under the
floorBG BranchGroup so picking can be localized to everything below
floorBG, excluding the walls attached to the
TransformGroup nodes are in the graph, and
landBG is attached directly to the top-level
sceneBG node. This means that the local coordinates used inside the
ColouredPlane objects are scene coordinates, and mapping between local and world values is unnecessary. This is an important ...