In computer graphics, two of the most complex techniques that are used in the process of approximating the scenes lit by global illumination are path and ray tracing. While they mutually share the same theory, they have created significantly different outcomes relative to the amount of computation complexity versus image quality.
Ray Tracing: In a Nutshell
Ray tracing is a method of image generation that simulates how the light acts when it comes into contact with all kinds of objects in the scene. The basic concept behind the method is that it involves tracing rays of light from the camera viewpoint out into the scene. Every ray decides how to color every pixel based on its interaction with the surfaces, which may mean reflections, refractions, or shadows.
One of the most basic concepts of ray tracing is reflection and refraction. In essence, ray tracing has been successful in coming up with photorealistic pictures of the complicated light behaviors through the firing of rays into the scene and thereafter computing their contact with objects. Classic ray tracing, however, quite frequently fails to execute under global illumination, which involves light bouncing around between surfaces, thus modifying the color and brightness of other parts within a scene.
Path Tracing: Detailed Approach
Path tracing is an extension of ray tracing that includes global illumination. An extension of the ray tracing algorithm, it follows not only the rays coming from the camera but from various random directions. Since the stochastic nature of light is simulated, one can see how light traverses a scene. Light will be reflected in different directions, further bouncing around a scene.
The greatest advantage of path tracing is being able to produce far more realistic lighting effects by basically supporting diffuse inter-reflections, caustics, and complicated light interactions in the core and thus being able to render scenes with challenging light. All these features of realism come at the expense of computational intensity. It converges to a noiseless image only at large numbers of samples; normally, this makes the time taken by rendering longer than that of standard ray tracing.
Comparative Analysis
The main difference between path tracing and traditional ray tracing lies in the way they treat the phenomena of light interaction. Conversely, the quality of the image from ray tracing is very high because of the exact reflection and refraction representation. However, it lacks many details in the global lighting model, which can make the final image less realistic if a complicated scene is illuminated. In contrast, path tracing actually handles significantly increased fine details with respect to lighting and generates by far more realistic images. But this, too, comes at a severe cost in computation.
Both techniques find their application and are powerful in computer graphics, though they have their specific strong and weak points. In simple words, ray tracing provides a handle to realize reflections and refractions very quickly and with high accuracy within a scene, while path tracing is useful where high realism and general lighting are being called for. These are the differences that, if appreciated by an artist and an engineer, will give him/her the right to choose the right approach among them for the specific rendering needs and available computational resources.
Arnold