Rendering

Rendering is the computational process of producing 2D image frames from a 3D scene description, simulating the propagation of light through the scene to determine each pixel's final color. Modern feature VFX renderers use ray tracing or path tracing, simulating light by tracing rays from the camera into the scene, bouncing off surfaces according to their material properties, and accumulating contributions from light sources. The dominant production renderers include: Arnold (now Autodesk-owned, used widely on features, biased path tracer with strong color management), RenderMan (Pixar's renderer, used on most Pixar features and many third-party features, REYES legacy combined with modern path tracing), Redshift (GPU-accelerated, popular in commercials and game cinematics), V-Ray (architectural and product visualization, occasional feature use), Karma (SideFX Houdini's native renderer), Cycles (Blender, increasingly used in professional contexts, open source), Octane (GPU-based, popular in motion design). Real-time renderers (Unreal Engine 5, Unity HDRP) have become viable for some film production via virtual production stages. Render times scale with: scene complexity (geometry triangle count), material complexity (subsurface scattering, hair, fur), lighting complexity (number of light sources, importance sampling), output resolution and bit depth, motion blur and depth of field samples, and noise threshold (path tracers progress until variance falls below a threshold). Reference: Pharr/Jakob/Humphreys 'Physically Based Rendering' is the canonical text.