cgp (prefi)

Scene graph

A data structure that organizes the contents of a 3D scene using a hierarchical structure

Tree

Represents a hierarchical nature of structure in a graphical form

Nodes

A tree consists of elements called

Child nodes

The successor of a node

Parent nodes

The predecessor of a node

Root node

The tree’s topmost node

Model matrix

Effectively stores location, orientation, and scale of an object

Transform of the object

Location, orientation, and scale of an object collectively

World transformation

The transform of an object relative to the root of the scene graph

Scene graph structure

Allows simple geometric shapes to be grouped together into a compound object into a single unit

Scene graph-based framework

Allows you to create interactive scenes containing complex objects

corresponding class (ex. Object3D class) shall contain three (3) items

A matrix to store its transform data 

A list of references to child objects

A reference to a parent object

Root node 

(Scene) 

Interior nodes used for grouping purposes 

(Group) 

Nodes corresponding to objects that can be rendered 

(Mesh) 

Virtual camera for rendering the point of view 

(Camera) 

Virtual light source that affects the shading and shadows 

(Light) 

The general shape and other vertex-related properties of each mesh 

(Geometry) 

The general appearance of an object 

(Material) 

The general initialization tasks and image rendering 

(Renderer)

Vertex array object (VAO)

associates vertex buffers to attribute variables/ allows geometric objects to be reused

vertex-related properties of each mesh (ex. Geometry class)

shall store Attribute objects that describe vertex properties, such as position and color

Geometric objects 

shall also store texture coordinates, for applying images to shapes, and normal vectors, for use in lighting calculations

In some cases, such as rectangles and boxes

the attribute data shall be listed directly.

For other shapes, such as polygons, cylinders, and spheres

the attribute data shall be calculated from mathematical formulas.

the general appearance of an object (ex. Material class) shall serve as a repository for three types of information related to the rendering process and the appearance of an object

the shader code (and the associated program reference), 

Uniform objects, and 

render settings

The render settings 

are the properties which are set by calling functions, such as the type of geometric primitive s (points, lines, or triangles), point size, line width, and so forth.

The base Material class 

shall initialize dictionaries to store uniform objects and render setting data. It shall also define functions to perform tasks such as compiling the shader program code and locating uniform variable references. Extensions of this class shall supply the actual shader code, a collection of uniform objects corresponding to uniform variables defined in the shaders, and a collection of render setting variables applicable to the type of geometric primitive being rendered.

The rendering function in the Renderer class shall require two ( 2 ) parameters

a scene object and 

a camera object

For each mesh in the scene graph, the renderer shall perform the tasks necessary before the function for drawing is called

These tasks include activating the correct shader program, binding a vertex array object, configuring render settings, and sending values to be used in uniform variables

There are three ( 3 ) required uniform variables by most shaders whose values are stored outside the material

the transformation of a mesh, 

the transformation of the virtual camera used for viewing the scene, and 

the perspective transformation applied to all objects in the scene

Though the uniform objects will be stored in the material for consistency

this matrix data shall be copied by the rendered into the corresponding uniform objects before they send their values to the GPU.