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.
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.
Displacement: Enables / Disables Displacement globally.
Motion Blur: Enables / Disables Motion Blur globally.
Medium/SSS: Enables / Disables Medium and SSS globally.
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.
Adaptive Tracing is a technique that solves difficult lighting scenarios, such as caustics from point lights, sun pool caustics and diffuse interreflections. This results in images with a higher dynamic range and lighting effects that were previously impossible.
Clamp Firefly: Enable this option to eliminate bright pixels from the final image.
Clamp Firefly (Level): Clamps the brightness of the light paths of the rendered image that have a value higher than the defined one.
Caustics: Enable this option to introduce reflective and refractive caustics.
Watch the Adaptive Tracing tutorial on YouTube: https://www.youtube.com/watch?v=-3lpNz6Lgf0
Adaptive Tracing needs to be enabled for the settings to affect the rendering.
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.
Out-of-Core rendering gives the GPU engine the option to use the mainboard’s memory when the scene does not fit the graphics card’s memory. You can select which parts of the scene should be transferred to the mainboard’s memory (Textures, Geometry, Accelerator and Film)
Textures / Geometry: Select which components will be affected by Out of Core.
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.