Reference/Release Notes/2.90/Cycles

= Blender 2.90: Cycles =

CPU Rendering
Intel Embree is now used for ray tracing on the CPU. This significantly improves performance in scenes with motion blur. Other scenes with high geometric complexity also benefit on average, depending on the scene contents.

GPU Rendering

 * OptiX is now available on all NVIDIA GPUs that support it, which is Maxwell or higher (GeForce 700, 800, 900, 1000 series).
 * NVLink support for CUDA and OptiX. When enabled in the Cycles device preferences, GPUs connected with an NVLink bridge will share memory to support rendering bigger scenes.
 * NVIDIA GPU rendering on macOS is no longer supported. Apple dropped support for CUDA drivers in macOS 10.14, and no recent Apple hardware uses NVIDIA graphics cards.

Hair
Hair curves are rendered differently due to the switch to Embree. GPU rendering was made to match Embree. There are now two shapes to choose from:


 * Rounded Ribbon: render hair as flat ribbon with (fake) rounded normals, for fast rendering. Hair curves are subdivided with a fixed number of user specified subdivisions. This gives relatively accurate results, especially when used with the Principled Hair BSDF and hair viewed from a typical distance. There may be artifacts when viewed closed up.
 * 3D Curve: render hair as 3D curve, for accurate results when viewing hair close up. This automatically subdivides the curve until it is smooth. This gives higher quality than any of the previous primitives, but does come at a performance cost. Especially on the GPU this is slower than previous primitives.

Sky Texture
The new Sky texture is an improved version of the Nishita single scattering sky model, and it accounts for altitude change as well as ozone absorption.



It includes a sun component with limb darkening effect.



Comparison between the old Hosek/Wilkie (left) and new Nishita (right) sky models:



Lighting from the Sky texture may be quite bright or dark depending on the time of day. Adjust the Exposure in the Film panel to compensate for this.

Denoising
Intel OpenImageDenoise is now supported for interactive denoising in the 3D viewport and for final renders. This works on any recent Intel/AMD CPU (with SSE 4.1).

Previously viewport denoising was only supported for NVIDIA GPUs using OptiX, and final render denoising with OpenImageDenoise was only possible in the compositor.

Performance of tiled denoising in final renders is still poor, we will investigate optimizing this.

Shadow Terminator

 * Per-object shadow terminator offset setting, to avoid artifacts with smooth normals on low-poly meshes. (c7280ce65b85)

Changes

 * Depth render pass for perspective cameras was changed to be more standard, matching OpenGL, Eevee and other renderers.
 * Error messages are now propagated to the viewport status overlay (instead of it only showing "Cancel").
 * Denoising is now enabled in the Render Properties for all view layers, in the Sampling > Denoising panel. Settings can still be fine-tuned per view layer, including disabling denoising for specific layers.