nXtRender Rendering Engines

There are three rendering engines. - Packet Mode, the Path Tracer, and the Hybrid Engine.

Packet Mode is the fastest for creating quick renderings. I does this by taking some shortcuts on how light, reflection and transparency are processed. The other engines use a more precise algorithm to process the end result for each pixel, but start out with a rough looking image for the first 100 or more passes until the various calculations for adjacent pixels start to converge.

Rendering Engines

Packet Mode

Packet Mode after 68 passes

The Packet Mode rendering engine provides high quality renderings quickly by approximating some things light lighting and reflection using 'packets'. Processes packets of rays. This produces a very good rendering in the shortest time.

The Packet Mode processes packets of rays, while the Path Tracer and Hybrid Engine process individual light paths.

Because of some shortcuts, such as Daylight Portals, and other aspects of the rendering process, Packet Mode create a usable image in fewer passes. Path Tracer often requires more passes before the image gets smooth.

Path Tracer

Path Tracer after 1500 passes.

The Path Tracer processes individual light paths This requires more passes, but produces better results.

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.

The Hybrid Engine

Hybrid Engine ater 625 passes.

The Hybrid Engineis faster per pass than the Path Tracer, and has special processing of Caustics for transparent and reflective surfaces.

This water scene was rendered for 625 passes - nine hours - with the Hybrid Engine:

Rendering Speed

In many cases individual passes in Path Tracer or the Hybrid Engine are faster than 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.

Slower Convergence

Because of some shortcuts, such as Daylight Portals , and other aspects of the rendering process, Packet Mode create a usable image in fewer passes. Path Tracer often requires more passes before the image gets smooth. In many cases individual passes in Path Tracer are faster, however the overall rendering process may take longer to complete.