Blender Master Class

Shadows in Blender Internal

Blender offers two ways to render shadows: ray tracing and shadow buffers.

Ray Tracing

The first method uses ray tracing to determine the parts of a mesh in shadow. Ray tracing “fires” rays out from the camera for each pixel in an image and draws them to the surface the pixel is facing. Further rays are drawn to the lights in the scene to determine whether that point is in light or shadow: If a ray can be drawn to the light without intersecting another object, the point is lit; otherwise, it is in shadow.

When there are multiple lights or soft shadows, multiple rays must be cast per pixel, increasing render times. The same goes for ray-traced reflections and transparency, where rays may be reflected or refracted ...