This document assumes you have previous experience with GIS software that uses a layer-based approach.
Most GIS software, such as ArcView and TatukGIS, use a layer-based approach. You have a layer for elevation, a layer for road data, and a layer for ortho-imagery such as color aerial photos or satellite-acquired photos.
Scenome uses a different approach.
As a 3D modeling product, Scenome uses the industry standard model definition format referred to as a directed acyclic graph but most often simply called a hierarchy. The atomic unit of a hierarchy is a node. Instead of having a "layer" for elevation, Scenome represents your elevation data with a node called a modifier. This modifier creates a 3D model of the terrain represented by the elevation imagery.
Scenome's hierarchy works like the folder explorer on your computer. You can store a folder in a folder, put files into folders, and organize your data in the manner which suits you best. Scenome's hierarchy allows you to organize your data more or less how you see fit, but for real-time graphics performance there are additional considerations.
Nodes have many functions that are very similar to layers but the most important related concept is the ability to turn the layer on and off. You can easily turn any individual node on and off - and you can turn an entire collection of nodes on and off if you wish. In Scenome the concept of a layer is analogous to the concept of a collection of nodes.
Relationships in the scene graph are described with the terms Parent, Child, and Sibling. List order can also specify a relationship if you assume that priority is derived from the order of the nodes.
Scenome has a relative small set of hierarchy nodes. Each type is discussed briefly.
The group node is used as a container element to store nodes of every type. You can turn a group on and off like a layer.
Like the group node, a level-of-detail node is used as a container. However the level-of-detail node has the ability to display its child nodes only when the camera is within range. You can turn a level-of-detail node on and off like a layer.
The mesh node stores geometry such as faces, edges, and vertices. The mesh node also stores the construction history - which is like having an individual undo stack for each mesh.
The modifier node serves as an operation on a mesh. Each time you modify the faces, edges, or vertices in a mesh, Scenome adds a modifier to the construction history. You can turn a mesh node on and off like a layer.
The link node serves as a hyperlink from one file to another file, just like a hyperlink on a web page.
The light node serves as a light source for meshes in the scene.
The material node defines the appearance of a surface including its lighting colors, transparency, and which texture, if any, is used.
A texture node is hyperlinked to an image file on disk. If a material node references a texture node, the image on disk is used to render a more realistic surface appearance. Ortho-imagery is a common example of an image file you might want to use as a texture.
Keep in mind the following: