Path Tracer
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The Path Tracer can provide a better quality finished product for many models (with a simpler setup), but does so at the expense of a more complex and time-consuming calculation. The Path Tracer begins by displaying a very grainy or “noisy” image which gradually refines and becomes smooth. This process is known as convergence. Some scenes will converge very quickly, others will take many hours.
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Comparison to nXt Packet Mode
nXt Packet Mode processes packets of rays, while nXt Path Tracer processes individual light paths.
Because of some shortcuts, such as Daylight Portals, and other aspects of the rendering process, nXt Packet Mode create a usable image in fewer passes. nXt Path Tracer often requires more passes before the image gets smooth.
Both of these renderings took several hours. You can see differences between the renderings - such as the reflected light from the ceiling lights on the ceiling which is smoother in the Path Tracer rendering.
Rendering Speed
In many cases individual passes in nXt Path Tracer are faster than nXt Packet Mode, however the overall rendering process may take longer to complete, because you will often need many, many more passes to achieve a good result.
As 16-core (or more) processors become available, then it will make more sense to use a many, many pass rendering solution.
Additional Notes
- In general, images rendered using the Path Tracer will take longer to converge than images rendered using the Standard method. Interior daylight simulations, particularly those scenes where the windows are relatively small, may take much longer. On the other hand, the Path Tracer is less sensitive to instancing, plants, and displacement maps. Models which rely heavily on these features may actually converge faster using the Path Tracer.
- The standard Packet Tracer algorithm produces a very high-quality simulation. For many models, the difference in quality between the Packet Tracer method and the Path Tracer can be very subtle, particularly if indirect lighting is enabled. The difference in quality may not be worth the extra processing time.
- The Path Tracer is almost always easier to configure and set up than the Packet Tracer method. Advanced settings such as reflection shaders, daylight portals, and ambient lighting, are not used when the Path Tracer engine is selected.
- Certain advanced effects, such as caustics or blurry transmission, can be calculated with better accuracy using the Path Tracer.