The upcoming Thea Version will support a feature (with primary usage for architectural visualization) that has been asked many times: Section Cuts. The idea of section cuts is that, without breaking your current model, you can define certain shapes (usually planes) cutting away the geometry and giving the possibility to take a "look inside".

In Thea Render context, section cuts are defined as planes that cut part of the scene. The cuts are defined per camera and they are making the geometry outside them, invisible to the camera. This means that the geometry is not actually removed but it is still there, contributing to the reflections, secondary bounces, etc.

In the upcoming Thea version a small advance in Thea material system will be also included, useful for those that aim for extra fine details when rendering.

This advance is about the coating absorption that can be wavelength dependent. The central idea is that the user defines now the absorption color at certain depth inside the coating (typically, 100 micro meters) using a standard color/texture control. This color becomes then the dominant one for any reflections coming from layers underneath.

Since the actual distance traveled by the reflected rays varies with the angle, the colored absorption creates a subtle but still observable effect where there is a simultaneous hue and saturation shift. The effect is "indeed there in real life" and can be seen in cases like metallic car paints and tinted wood varnish.
At the renders provided, you can see the transition and hue shift with viewing angle. This is more evident as you see nearer the edges of the model.

As part of our constant focus to evolve Thea Render and after intensive development, the upcoming release will have a substantially improved Shadow Catcher:

- Sun-Sky and omni point lights in general are now supported to complement existing IBL image support.

- Realistic shadows generation by taking into account directionality of IBL images.

- Support for horizontal infinite plane in all render modes (including Presto) for easier and efficient workflow.

- Shadow catcher can now work also in conjunction with a reflective BSDF. This gives the ability to have reflections on the shadow catcher plane, with arbitrary (user defined) colors, reflectivity and roughness.

When we started implementing the material system from scratch, we started too strict on what should be allowed and what not. In this context, we went for a relatively restrictive option, that we call the Fresnel curve - it is the user edited curve that can be seen in almost all material BSDFs. Although the Fresnel curve is the most physically-based strict approach, it is also restrictive with respect to what can be achieved with it.

The new Fresnel Ramp procedural is much more powerful than the existing Fresnel reflectance curve. First of all, it can be used with any component (for example, diffuse) and not just the reflectance. We added many ways of adjusting its effect, with more parameters and direct curve editing. It is even possible to create some psychedelic materials if one wants to!

Of course, the most ideal way to use the new procedural is probably for various cloth types, such as satin, velvet and jeans.