Immediate Mode, Retained Mode

• Immediate Mode: issue drawing commands explicitly; the graphics API does not know how to build the 3D world on its own; examples: OpenGL, DirectX
• Retained Mode: construct and store the 3D world using the API; rendering is handled automatically; examples: Java3D, OpenInventor, OpenSceneGraph, most game engines; usually a scenegraph is created to store the 3D world hierarchically

Photo Realism

• Up to now, we even used only local illumination models, which lack shadows and reflections.
• Global illumination:
• Ray Tracing
• Radiosity
• Note that in commercial software these terms are used differently: Global illumination is understood to include indirect illumination; radiosity is used as a synonym for that notion of global illumination.
• Computer graphics (real-time as well as offline) hardly delivers photorealistic images. Some points where this is obvious:
• soft shadows
• blurred reflections
• caustics

Graphics Hardware

• Hard-edged textures with little computational overhead
• Motion blur using anisotropic filtering
• Plausible cloth wrinkles