Thea for SketchUp offers two rendering modes: Interactive Mode and Production Mode.
IR modes allow you to not only render the model as a static image, but also interactively move the camera around the model, adjust shadows and materials, modify the model, and see the rendering being updated. Engines that offer Interactive Mode are: Presto & Adaptive AMC.
PR mode is used for final renderings 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 rendering engine that has been written from the ground up and is optimized for simultaneous GPU and CPU execution, thus harnessing all your computing power. The engine has been optimized 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 necessary 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 Depth: This is a separate value that controls tracing depth for diffused surfaces. Setting Diffuse Depth to 0 removes all light bounces from the scene, leaving only the direct light.
Clamp Level: Clamps the evaluation of a pixel, improving antialiasing. The number corresponds to the clamping limit. When you use a value higher than 1, clamping becomes less effective for antialiasing. When you use a value less than 1, clamping becomes more effective, but it also more aggressively lowers the brightness of the image.
Bucket Render: Rendering high resolution images with multiple channels is usually an issue for GPUs, but with the use of bucket rendering, you can overcome this limiting factor and improve scalability as well.
Ambient occlusion can be used to mimic a part of global illumination, making the rendering engine 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 a white color.
Intensity: This value defines the intensity of the ambient occlusion used.
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 (e.g., solid glass or water). If you notice that you get dark areas on solid glass, this is often the result of the Internal Reflection Depth being too low, not because of the Transperency Depth.
SSS Depth: Determines the extended tracing depth for subsurface scattering (SSS) materials. In some cases increasing this value is needed to increase the brightness of brightly colored, and dense SSS materials. Not available when Diffuse Depth is enabled.
Supersampling: This corresponds to the supersampling used for the image output (i.e., internal resolution multiplier for antialiasing enhancement).
'None' corresponds to no supersampling at all, 'Normal' to 2x2, and 'High' to 3x3. 'Auto' corresponds to no supersampling for the biased engine (disabled by default).
Setting supersampling to a higher level generally improves antialiasing of the output, but increases memory demands for storing the image (by 4 times for 'Normal' and by 9 times for 'High'). The time needed to render the scene is also increased for a biased engine.
Thea Render supports a superior, unbiased core, which is one of the most advanced on the market and delivers stunning images without any compromises. All possible paths of lighting transfer are explored, delivering the highest accuracy without any artifacts. Sun-pool caustics and terminator artifacts 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 optimal for extremely difficult indirect and caustic lighting.
Thea biased engine (Adaptive BSD) uses interpolation schemes such as an irradiance cache to render in shorter times and is implemented so more effort can be put where it is needed most.
Furthermore this effort is driven by perceptual criteria, generating high-quality results that are perceived naturally.
The Adaptive BSD engine uses a preset workflow to let the user control the engine. There are several presets for interiors and exteriors, as well as different qualities for each (draft, low, high, etc).
The Adaptive AMC engine is based on the Unbiased TR2 engine but with shortcuts to make it faster. It should be preferred for difficult, indirect lighting situations (e.g., indirect caustics) and it can be used in both Interactive and Production 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 there is no direct impact on render times.
Adaptive Bias: By 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.