Thea for Rhino offers two rendering modes. Interactive and Production mode.
IR mode allow you to not only render the model as a static image but also interactively move the camera around the model, adjust materials and lights, modify the model and see the rendering being updated. Engines that offer Interactive Rendering are: Presto & Adaptive AMC.
PR mode is used for final rendering where changes to the scene do not affect the final image while rendering. All engines can be used in Production Mode
(Presto, Adaptive AMC, Adaptive BSD, Unbiased TR1/TR2)
Thea Presto is an advanced render engine that has been written from the ground up and is optimised for both GPU and CPU execution simultaneously, harvesting all your computing power. The engine has been especially tuned for fast interactive rendering. This pushes GPU+CPU computing to the limits while keeping the high photorealistic quality of Thea Render.
Tracing Depth: This is an important parameter for Progressive Engines. Increasing this parameter may be needed for certain cases where there are a lot of mirrors or dielectrics in the scene but it has a direct impact on render times.
Diffuse Interreflection: is a separate value to control tracing depth for diffused surfaces. Setting Diffuse Depth to 0 will remove all light bounces from the scene leaving only the direct light.
Extended Tracing: Extended Tracing can efficiently render scenes with transparent objects or materials with Subsurface Scattering while using a lower Tracing Depth.
Transparency Depth: Determines the Extended Tracing Depth for all transparent materials like Thin Glass, Glass and Clip Map.
Internal Reflection Depth: Determines the Extended Tracing Depth for transparent materials that have refraction and total internal reflection. These materials are created with the use of the Glass layer (for example solid glass or water). If you notice that you get dark areas on solid glass, the cause is often because of too low Internal Reflection Depth and not due to the Transparency Depth.
SSS Depth: Determines the Extended Tracing Depth for Subsurface Scatering (SSS) materials. In some cases increasing this value is needed to increase the brightness of bright colored dense SSS materials. (Not available when Diffuse Interreflection is enabled)
Clamp Level: Clamps the evaluation of a pixel, improving antialiasing. The number corresponds to the clamping limit. Higher than 1, clamping becomes less effective for antialiasing while less than 1 it becomes more effective but also lowering the brightness of the image more aggresively.
Bucket Rendering: Rendering high resolution images with multiple channels is usually an issue for GPUs but with the use of Bucket Rendering implementation, we are able to overcome this limiting factor and improve scalability as well.
Ambient Occlusion: used to mimic a part of global illumination making the engine to render faster.
Distance: this is the maximum distance that the sample may be evaluated to an intermediate (gray) color. After that distance, the sample is evaluated to white color.
Intensity: this value defines the intensity of the Ambient Occlusion used.
Denoiser: select the denoiser method to be used. Available methods are NVIDIA OptiX and Non Local Means. To enable the denoiser make sure to also enable the Denoise channel in the Channels tab.
Thea Render supports a superior unbiased core which is one of the most advanced in the market and delivers stunning images without any compromises. All possible paths of lighting transfers are explored, delivering the highest accuracy without any artifacts. Sun‐pool caustics and terminator artifact are robustly handled offering stunning results.
These two engines have no settings and are controlled only by the Sample and Time Limit. Unbiased engine TR1 is optimal for exteriors and scenes with dominant direct lighting while unbiased engine TR2 is optmal for extremely difficult indirect and caustc lightng.
The Adaptive AMC engine is based on the Unbiased TR2 engine but with shortcuts to make it faster. It should be preffered for difficult indirect lighting situations (e.g. indirect caustics) and it can be used in both Interactive and Producton Mode.
Tracing Depth: Just like in the Presto Engine, this is an important parameter for Progressive Engines. Increasing this parameter may be needed for certain cases where there are a lot of mirrors or dielectrics in the scene but it has a direct impact on render times.
Adaptive Bias: Increasing this value, several difficult paths are taken out of computations, making it faster.
Caustics: Removes the caustics path. In general, it should always be enabled.
Thea Biased engine (Adaptive BSD) uses interpolation schemes such as irradiance cache to render in shorter times and is implemented in a way that more effort is put where it is needed most. Furthermore this effort is driven by perceptual criteria generating high quality results that are perceived naturally. Adaptive BSD settings can be divided in two sections. Biased RT and Biased GI settings.
Biased RT: contains the basic parameters in order to trace reflecting and refracting objects and evaluate direct lighting.
Biased GI: contains the basic parameters that control the quality of Global Illumination.
Ray Tracing Quality: defines the quality of raytracing.
Tracing Depth: This is the main parameter influencing tracing depth for biased engine. Increasing this parameter may be needed for certain cases where there are a lot of mirrors or dielectrics in the scene, but it has a direct impact on render time.
Glossy Depth: controls tracing depth for blurred reflections/refractions. Keeping this value low will save evaluations on rough materials that in many cases contribute little to the overall image.
Trace Reflections: enables tracing of perfect reflections (glass reflection and glossy/ coating zero roughness reflection).
Trace Refractions: enables tracing of perfect refractions (glossy/coating zero roughness refraction).
Trace Transparencies: enables tracing of glass and alpha mapping transparencies.
Trace Dispersion: enables dispersion for biased engine. Dispersion will raise render times considerably for the objects that exhibit this property, so having this option disabled for quick test renders is preferred.
Direct Lighting: enables/disables the direct light component of the biased engine.
Blurred Reflections: If enabled, blurred reflections and refractions will be traced in the scene. The maximum tracing depth is set by the ray tracing Glossy Depth parameter.
Evaluate GI: defines if Global Illumination will be evaluated or not.
Min Blurred Subdivs: controls the minimum number samples (in a power‐of‐two relation) taken on a blurred reflection/refraction.
Max Blurred Subdivs: controls the maximum number samples (in a power‐of‐two relation) taken on a blurred reflection/refraction.
Ambient Occlusion: enables/disables the Ambient Occlusion for biased engine.
Samples: The stochastic samples taken on the hemisphere to estimate ambient occlusion. The more samples the better the accuracy but it will also take more time for the computation.
Distance: the maximum distance that the sample may be evaluated to an intermediate (gray) color. After that distance, the sample is evaluated to white color.
GI Quality: controls the quality of Global Illumination.
Scene Type: select between interior and exterior type. Using the interior type will make the engine to make use of the Field Mapping technique which accelerates these type of scenes.
Caustics: Enables/Disables caustics. Caustics are the photons that have been reflected or transmitted via at least one specular surface (like water or glass) before hitting a diffuse surface.
Captured Photons: This parameter corresponds to caustic photons captured in the map by all emitters. Usually, caustics need to be quite detailed and this value should be as high as possible. To avoid excessive memory demands, user should also control the lights emitting caustic photons and surfaces capturing caustics, to keep them as few as possible.
Estimation Photons: This is the number of caustic photons used for irradiance estimation. The higher the value the more blurry the results. Note that increasing this value will also have an impact on render times.