Lighting

OmegaEngine uses a realtime lighting system that supports multiple light types and shadowing techniques.

Lighting model

The default surface shader (GeneralShader) implements Blinn-Phong lighting, which provides:

• Diffuse lighting - Light scattered equally in all directions from a surface
• Specular highlights - Bright spots that appear on shiny surfaces
• Ambient lighting - Base illumination level to prevent completely dark areas
• Emissive lighting - Light emitted by surfaces without any light source shining on them (not itself treated as a light source illuminating other surfaces)

See OmegaEngine.Graphics.LightSources for details on the types of light sources.

Shadowing

OmegaEngine supports two distinct shadow casting methods for different purposes.

Bounding sphere shadows

PositionableRenderables can cast realtime shadows on each other using a simple bounding sphere approximation. This provides easy shadowing with low performance impact, but with low fidelity: when an object is only partially within a shadow, it gets darkened in its entirety, rather than showing a shadow "line" across its surface.

This technique:

• projects cones starting at light sources and passing through shadow casters, matching their bounding sphere's radius
• tests whether shadow receivers are partially, fully or not at all within those cones

Each PositionableRenderable can be a shadow caster, a shadow receiver, both or neither.

Terrain self-shadowing

Terrain rendering supports high-fidelity self-shadowing using pre-calculated occlusion interval maps (see OcclusionIntervalMap).

This technique:

• calculates which angles each terrain point is visible from
• stores the data in occlusion interval maps
• uses this data during rendering to determine if terrain points are in shadow
• provides accurate terrain shadows without real-time calculations