Editing Blender (software) (section)

====Cycles====
[[File:Rendering using Cycles in Blender.webm|thumb|Rendering of different materials using the Cycles render engine]]
Cycles is a [[Path Tracing|path-tracing]] [[Rendering (computer graphics)|render engine]] that is designed to be interactive and easy to use, while still supporting many features.<ref name="manual-cycles-intro">{{cite web|title=Introduction — Blender Reference Manual|url=http://www.blender.org/manual/render/cycles/introduction.html|website=www.blender.org|access-date=2015-10-18}}</ref> It has been included with Blender since 2011, with the release of Blender 2.61. Cycles supports with AVX, [[AVX2]] and [[AVX-512]] extensions, as well as CPU acceleration in modern hardware.<ref>{{Cite web|last1=Jaroš|first1=Milan|last2=Strakoš|first2=Petr|last3=Říha|first3=Lubomír|title=Rending in Blender Cycles Using AVX-512 Vectorization|url=https://www.ixpug.org/documents/1520629330Jaros-IXPUG-CINECABlender5.pdf|access-date=March 2, 2023}}</ref>

=====GPU rendering=====
Cycles supports [[GPU]] rendering, which is used to speed up rendering times. There are three GPU rendering modes: [[CUDA]], which is the preferred method for older [[Nvidia]] graphics cards; [[OptiX]], which utilizes the hardware ray-tracing capabilities of Nvidia's [[Turing (microarchitecture)|Turing architecture]] & [[Ampere (microarchitecture)|Ampere architecture]]; [[Heterogeneous-compute Interface for Portability|HIP]], which supports rendering on [[Advanced Micro Devices|AMD]] [[Radeon]] graphics cards; and [[oneAPI (compute acceleration)|oneAPI]] for [[Intel]] and [[Intel Arc]] GPUs. The toolkit software associated with these rendering modes does not come within Blender and needs to be separately installed and configured as per their respective source instructions.

Multiple GPUs are also supported (with the notable exception of the EEVEE render engine<ref>{{cite web|title=Limitations — Blender Manual|url=https://docs.blender.org/manual/en/latest/render/eevee/limitations.html#multiple-gpu-support|website=www.blender.org|access-date=2023-01-12}}</ref>) which can be used to create a [[render farm]] to speed up rendering by processing frames or tiles in parallel—having multiple GPUs, however, does not increase the available memory since each GPU can only access its own memory.<ref>{{cite web|title=GPU Rendering — Blender Reference Manual|url=http://www.blender.org/manual/render/cycles/gpu_rendering.html|website=www.blender.org|access-date=2015-10-18}}</ref> Since Version 2.90, this limitation of [[Scalable Link Interface|SLI]] cards is broken with Nvidia's [[NVLink]].<ref>{{cite web|url=https://www.blender3darchitect.com/blender-cycles/blender-2-90-cycles-updates-in-multi-gpu-nvlink/|title=Blender 2.90: Cycles updates in Multi GPU (NVLink) • Blender 3D Architect|date=10 August 2020}}</ref>

Apple's Metal API got initial implementation in Blender 3.1 for Apple computers with [[Apple M1|M1]] chips and [[AMD graphics processing units|AMD graphics cards]].<ref>{{cite web|url=https://wiki.blender.org/wiki/Reference/Release_Notes/3.1/Cycles|title=Reference/Release Notes/3.1/Cycles - Blender Developer Wiki}}</ref>

{| class="wikitable"
|+Supported features<ref>{{cite web|url=https://docs.blender.org/manual/en/latest/render/cycles/gpu_rendering.html|title=GPU Rendering — Blender Manual}}</ref>
! Feature
! CPU
! CUDA
! OPTIX<ref>{{Cite web|url=https://projects.blender.org/blender/blender/issues/69800|title=Cycles Optix feature completeness|website=Blender Projects}}</ref>
! HIP
! oneAPI
! Metal
|-
| Hardware Minimum for 3.0
| x86-64 and other 64-Bit<ref>{{Cite web|url=https://packages.debian.org/search?keywords=blender|title=Debian -- Package Search Results -- blender|website=packages.debian.org}}</ref>
| Cuda 3.0+: Nvidia cards Kepler to Ampere (CUDA Toolkit 11.1+)<ref>{{cite web|url=https://wiki.blender.org/wiki/Building_Blender/CUDA|title=Building Blender/CUDA - Blender Developer Wiki}}</ref>
| OptiX 7.3 with driver 470+: Full: Nvidia RTX Series; Parts: Maxwell+
| AMD RDNA architecture or newer, Radeon Software Drivers (Windows, Linux)
| Intel Graphics Driver 30.0.101.3430 or newer on Windows, OpenCL runtime 22.10.23904 on Linux
| Apple Computers with Apple Silicon in MacOS 12.2, AMD Graphics Cards with MacOS 12.3
|-
| Basic shading
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
|-
| Shadows
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
|-
| [[Motion blur]]
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
|-
| Hair
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
|-
| Volume
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
|-
| [[Subsurface scattering]]
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
|-
| [[Open Shading Language]] (1.11) (OSL 1.12.6 in 3.4)
| {{yes}}
| {{no}}
| {{partial}}<ref>{{cite web|url=https://docs.blender.org/manual/en/latest/render/shader_nodes/osl.html|title=Open Shading Language - Blender 4.1 Manual}}</ref>
| {{no}}
| {{no}}
| {{no}}
|-
| Correlated multi-jittered sampling
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
|-
| Bevel and AO shaders
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
|-
| Baking<ref>{{cite web|url=https://docs.blender.org/manual/en/latest/render/cycles/baking.html|title=Render Baking — Blender Manual}}</ref>
| {{yes}}
| {{yes}} 
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
|-
| Can use CPU memory
| {{Clear}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
| {{yes}}
|-
| Distribute memory across devices
| {{yes}} with render farm<ref>{{cite web|url=https://rentaflop.com|title=rentaflop}}</ref><ref>{{cite web|url=https://www.sheepit-renderfarm.com/index.php|title=SheepIt Render Farm}}</ref>
| {{yes}} with NVLink
| {{yes}} with NVLink
| {{no}}
| {{no}}
| {{no}}
|-
! colspan="67" |Experimental features
|-
| Adaptive [[Subdivision surface|subdivision]]<ref>{{cite web|url=https://docs.blender.org/manual/en/latest/render/cycles/object_settings/adaptive_subdiv.html|title=Adaptive Subdivision — Blender Manual}}</ref>
| {{table-experimental}}
| {{table-experimental}}
| {{table-experimental}}
| {{table-experimental}}
| {{table-experimental}}
| {{table-experimental}}
|}

=====Integrator=====
The integrator is the core [[rendering algorithm]] used for [[Rendering equation|lighting computations]]. Cycles currently supports a [[path tracing]] integrator with direct light sampling. It works well for a variety of lighting setups, but it is not as suitable for [[Caustic (optics)|caustics]] and certain other complex lighting situations. [[Ray tracing (graphics)|Rays are traced]] from the camera into the scene, bouncing around until they find a light source (a lamp, an object material emitting light, or the world background), or until they are simply terminated based on the number of maximum bounces determined in the light path settings for the renderer. To find lamps and surfaces emitting light, both indirect light sampling (letting the ray follow the surface [[Bidirectional scattering distribution function|bidirectional scattering distribution function, or BSDF]]) and direct light sampling (picking a light source and tracing a ray towards it) are used.<ref>{{cite web|title=Integrator — Blender Reference Manual|url=http://www.blender.org/manual/render/cycles/settings/integrator.html#integrator|website=www.blender.org|access-date=2015-10-18|archive-url=https://web.archive.org/web/20151009124836/http://www.blender.org/manual/render/cycles/settings/integrator.html#integrator|archive-date=2015-10-09|url-status=dead}}</ref>

The default path tracing integrator is a "pure" path tracer. This integrator works by sending several [[light rays]] that act as [[photon]]s from the camera out into the scene. These rays will eventually hit either: a light source, an object, or the world background. If these rays hit an object, they will bounce based on the angle of impact, and continue bouncing until a light source has been reached or until a maximum number of bounces, as determined by the user, which will cause it to terminate and result in a black, unlit pixel. Multiple rays are calculated and averaged out for each pixel, a process known as "sampling". This sampling number is set by the user and greatly affects the final image. Lower sampling often results in more noise and has the potential to create "fireflies" (which are uncharacteristically bright pixels), while higher sampling greatly reduces noise, but also increases render times.

The alternative is a branched path tracing integrator, which works mostly the same way. Branched path tracing splits the light rays at each intersection with an object according to different surface components,{{Clarify|reason=|date=December 2019}} and takes all lights into account for shading instead of just one. This added complexity makes computing each ray slower but reduces noise in the render, especially in scenes dominated by direct (one-bounce) lighting. This was removed in Blender 3.0 with the advent of Cycles X, as improvements to the pure path tracing integrator made the branched path tracing integrator redundant.<ref>{{cite web |title=Cycles X |url=https://code.blender.org/2021/04/cycles-x/#deprecation |website=Blender Developer Blog |date=23 April 2021 |access-date=2024-07-16 |archive-url=https://web.archive.org/web/20240706015139/https://code.blender.org/2021/04/cycles-x/#deprecation |archive-date=2024-07-06}}</ref>

=====Open Shading Language=====
Blender users can create their own [[Node (computer science)|nodes]] using the [[Open Shading Language]] (OSL); this allows users to create stunning materials that are entirely procedural, which allows them to be used on any objects without stretching the texture as opposed to image-based textures which need to be made to fit a certain object. (Note that the shader nodes editor is shown in the image, although mostly correct, has undergone a slight change, changing how the UI is structured and looks.<ref>{{cite web|url=https://docs.blender.org/manual/en/latest/render/shader_nodes/index.html|title=Shader Nodes — Blender Manual}}</ref>
[[File:Blender shader node editor showcasing a Moldy Gold Materiel.png|thumb|400x400px|Using the node editor to create a moldy gold material]]

=====Materials=====
Materials define the look of [[polygon mesh|meshes]], [[Non-uniform rational B-spline|NURBS curves]], and other geometric objects. They consist of three [[shader]]s to define the mesh's surface appearance, volume inside, and surface displacement.<ref name="manual-cycles-intro" />

The ''surface shader'' defines the light interaction at the surface of the mesh. One or more bidirectional scattering distribution functions, or [[Bidirectional scattering distribution function|BSDFs]], can specify if incoming light is reflected, refracted into the mesh, or absorbed.<ref name="manual-cycles-intro" /> The [[Alpha compositing|alpha value]] is one measure of translucency.

When the surface shader does not reflect or absorb light, it enters the volume (light transmission). If no volume shader is specified, it will pass straight through (or be refracted, see [[Refractive index|refractive index or IOR]]) to another side of the mesh.

If one is defined, a ''volume shader'' describes the light interaction as it passes through the volume of the mesh. Light may be scattered, absorbed, or even emitted{{Clarify|reason=|date=December 2019}} at any point in the volume.<ref name="manual-cycles-intro" />

The shape of the surface may be altered by ''displacement shaders''. In this way, textures can be used to make the mesh surface more detailed.

Depending on the settings, the displacement may be virtual-only modifying the [[surface normals]] to give the impression of displacement (also known as [[bump mapping]]) – real, or a combination of real displacement with bump mapping.<ref name="manual-cycles-intro" />