Ray casting is a fundamental rendering technique in computer graphics that brings 3D perspectives to life from 2D maps. Developed in the 1960s, this fast and efficient method traces rays from a viewpoint into a 3D scene, creating a projection based on where those rays intersect objects.
How Ray Casting Works
Imagine light emanating from your eye in straight lines. When these "rays" hit an object, they may be:
- Absorbed
- Reflected
- Refracted
Ray casting calculates how much light follows each path, determining the brightness and color of objects at intersection points. This information is then translated into pixel values for the final image.
Unlike more complex ray tracing, ray casting doesn't recursively trace secondary rays. This makes it faster but less photorealistic.
Applications of Ray Casting
Ray casting found early success in video game development, particularly for creating pseudo-3D environments from 2D maps. Some key advantages include:
- Speed and simplicity
- Efficient computation (one calculation per vertical screen line)
- Ability to work within geometric constraints
Beyond gaming, ray casting is widely used in:
- Animation and CGI
- Television and film production
- Computational geometry
Ray Casting in Video Games
The 1992 game Wolfenstein 3D popularized ray casting for creating immersive 3D-like environments. While modern games use more advanced techniques, ray casting principles still underpin many 3D rendering engines.
Ray casting allowed games to create the illusion of 3D worlds while limiting player movement to maintain performance. This technique scans the screen horizontally, projecting vertical columns based on intersection calculations.
The Ray Casting Method
Ray casting typically involves:
- A direction vector representing the viewer's orientation
- A perpendicular camera plane defining the rendered image shape
- Tracing rays for each pixel to find the nearest intersecting object
- Applying shading based on light sources and material properties
More complex implementations may use algorithms for:
- Line drawing
- Creating shaded images
- Calculating volumes and physical properties
Ray Casting Games
Many classic and modern games utilize ray casting, including:
- Wolfenstein 3D
- Rise of the Triad
- Blake Stone series
- Catacomb 3-D
- DUGA
- VRG
While some of these titles are decades old, they showcase the enduring impact of ray casting on game development.
Conclusion
Ray casting remains a valuable technique in computer graphics, offering a balance of speed and visual fidelity. While it may not produce photorealistic results, its efficiency and versatility ensure its continued relevance in gaming, animation, and beyond.