What speaks for and against Path Tracing and REYES.

In practice, the question of the right rendering engine to create a 3D configurator often arises. In this article we would like to discuss the advantages and disadvantages of Path Tracing and REYES. Note that the use of REYES does not exclude the use of raytracing, which continues to be used on REYES for all secondary rays.

Here you will find a brief explanation of the advantages and disadvantages of the individual options.

Path Tracing

Advantages:

• Efficient rendering of dense mosaic-like geometries and dense scenes (forests, crowds, etc.)
• Massive instancing enables memory efficient rendering of trees/crowds and other redundant scene elements.
• Shading is usually “sharper” because shading is performed on each partial sample (and not per pixel as in REYES). Although it is possible to achieve a similar result with REYES by increasing the shading rate, this is usually avoided as it affects performance. An example of this sharpening advantage is the higher quality contouring.
• Scales better than REYES with an increased number of cores.
• Supports multi-light output.
• Supports geometric camera projections.

Disadvantages:

• Slower with displacements.
• You need more samples to get a smooth (noise-free) motion blur and depth of field. This happens because it is actually more precise than REYES and there are more details in the motion blur effect, but it also causes more noise.
• Increasing pixel samples (to reduce aliasing and noise) has a direct impact on performance (but has no impact on the sampling of indirect lighting).

REYES.

Advantages:

• Extremely efficient reproduction of curved surfaces of medium to large size – surfaces that include more than a few pixels in the image.
• High-quality motion blur and depth of field are extremely fast. The reason for this is that the shading calculation is decoupled from the blanking calculation.
• Displacements are performed at lower costs than with deim Path Tracing (micro polygons).
• Efficient rendering of liquids by under-sampling the screen space.
• Efficient rendering of millions of particles.
• Performance virtually independent of oversampling (pixel samples). This makes it easy (and fast) to render images without noise and aliasing.
• More efficient than path tracing with simultaneous multi-camera rendering (as in the case of 3D stereo rendering).
• Ability to efficiently distribute the display of a single image across multiple machines.

Disadvantages:

• Loss of performance in the representation of dense mosaic-like geometries (i.e. objects with a density of hundreds or thousands of surfaces covering only a few pixels).
• Not suitable for displaying scenes with high “pixel complexity” (e.g., a set seen from a distance).
• Motion Blur Shading is an approximation. For example, a rotating wheel will blur the reflective shine along with other details on the wheel, while the shine should remain sharp.
• Takes up more memory when used in addition to the raytracing function (e.g. for GI). This is because both raytracing and REYES data structures need to be maintained.

Thank you very much for your visit.