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Appleseed 2.0 Expands SSS, NPR and Adaptive Sampling

Patrick Poti
02.09.2020
Appleseed 2.0 adds random-walk SSS, NPR shading, false-colour analysis, tile-based adaptive sampling and Substance Painter support.

Archive republication: This article was originally published on 2 September 2020. It has been translated into English and lightly updated for clarity while preserving the original reporting and context.

This article originally appeared in Digital Production 02 : 2019.

Version 2.O of the path tracing render engine Appleseed has been given a number of features that are of interest to the visualisation sector. Officially, the open source software is still in the beta phase, but more and more feature gaps are being closed. The engine is interesting because it is available for 3ds Max and Maya as well as for Blender and the lookdev software Gaffer. If you are not at home in any of these programmes, you can try out Appleseed as standalone software Appleseed Studio. Some of the features, such as the visualisation of light paths, are only available there.

Like Cycles, Appleseed is a so-called production renderer, which means that it was not developed for scientific research, but with the requirements of daily work in computer graphics in mind. Stability, usability and performance are therefore also taken into account. Digital Production already presented Appleseed in issue 18:04. This article deals with the new features in version 2.0.

Random Walk SSS Galore

The implementation of Subsurface Scattering (SSS) based on the random walk algorithm has been massively upgraded. SSS can now be used in the classic diffuse form as well as for the Glass BSDF with roughness control. The newly added parameter for anisotropy further increases realism. Random Walk SSS can be selected as a profile in the SSS-Closure. A separate closure has been added for glass with SSS.

The paths of chance are unfathomable – an example of the quality of the new Random Walk Subsurface Scattering (SSS) shader. Model, textures and environment map by 3D Scan Store, skin shader by Juan Carlos Gutiérrez
Toon with Outline – With Appleseed you can now not only realise toon shading, you also get the outline. Model by Brice Laville, concept by Tom Robinson, render by Esteban Tovagliari as a participant in the Rolling Teapot competition organised by RenderMan

NPR makes its entrance

If you want to work in the style of cartoons or technical drawings, i.e. do so-called non-photorealistic rendering (NPR), you can achieve this using the new NPR Shading and NPR Contour closures. Both are also available as AOV or render layers.

False colours

Appleseed can now also apply post-processing to the render without the need for additional software. The system is not quite ready yet, but can already be used to obtain a false colour representation of the render. The relative luminance for Rec. 709 is displayed using pre-defined colour maps or colour maps defined using an image. Five maps known from Matlab and Matplotlib are supplied. In future, photometric luminance (in cd/m²), radiance (in W/sr/m²) and irradiance (in W/m²) will also be able to be displayed using false colours. In addition to the false colours, lines of equal relative luminance, so-called isolines, and a legend can also be drawn in.

False colours – Appleseed can now be used to display the relative luminance according to Rec. 7O9 using false colours. Five maps known from Matlab and Matplotlib are included: Inferno, Jet, Magma, Plasma and Viridis. However, you can also define your own maps. Scene by BlendSwap user Jay-Artist, converted into Mitsuba format by Benedikt Bitterli, then into Appleseed format using the mitsuba2appleseed.py script included with Appleseed

Adaptive sampling for tiles instead of pixels

With adaptive sampling, difficult or noisy areas of a render are sampled more finely than low-noise areas. Previously, this was done in Appleseed on a pixel basis. The new implementation now works on entire tiles and offers significantly better performance. Two new AOVs show the relative distribution of samples and noise across all pixels in the image.

Direct comparison of adaptive sampling – the old and the new tile-based adaptive sampler from Appleseed on the left and right respectively. Both images had the same render time, the result of the new sampler on the right shows a significantly lower noise level. Scene from https:// renderman.pixar.com/cookies-and-milk

Compatible with Substance Painter

Anyone working with the metallic/roughness workflow from Substance Painter will now also find it directly in Appleseed via the SBSPBR shader. It has been optimised to reproduce the look from Substance Painter as accurately as possible and supports a large number of the textures that can be exported from Substance Painter, such as ambient occlusion, mattes, anisotropy, etc.

Substance – Example render of some materials created in Substance Painter with Appleseed’s Substance-compatible OSL shader

Pathfinder

A very nice tool, which unfortunately can only be used in Appleseed Studio so far, is the display of light paths. Since version 2.0 beta, the light paths for entire areas can also be displayed using the box selection tool. This display can now be moved in all directions. If you change the perspective when viewing the paths, this is no longer automatically transferred to the rendering. If you also want to change the render view, you can do this via a new button in the interface. In the light path view, the geometry in the scene is now displayed in a darker colour so that the paths in the display are more contrasty and therefore easier to recognise.

Pathfinder – Light paths can now be displayed not only from individual pixels, but also from larger areas defined using the box selection tool. In this example, a point on the front of the glass. The paths reflected on the glass are black because they hit the dark surroundings

Conclusion

The development of Appleseed is currently proceeding relatively quickly. Since the last report in issue 04:18 of DP, several features have been implemented that make Appleseed interesting for the visualisation sector, above all the new false colour representations including isolines and the improvements in the representation of light paths

Patrick Poti Author