Retained mode explained

Retained mode in computer graphics is a major pattern of API design in graphics libraries,^[1] in which

• the graphics library, instead of the client, retains the scene (complete object model of the rendering primitives) to be rendered and
• the client calls into the graphics library do not directly cause actual rendering, but make use of extensive indirection to resources, managed thus retained by the graphics library.^[2] It does not preclude the use of double-buffering.^[3]

Immediate mode is an alternative approach. Historically, retained mode has been the dominant style in GUI libraries;^[4] however, both can coexist in the same library and are not necessarily exclusionary in practice.^[5]

Overview

In retained mode the client calls do not directly cause actual rendering, but instead update an abstract internal model (typically a list of objects) which is maintained within the library's data space. This allows the library to optimize when actual rendering takes place along with the processing of related objects.

Some techniques to optimize rendering include:

• managing double buffering^{[6] [7]}
• treatment of hidden surfaces by backface culling^[8] /occlusion culling (Z-buffering)^[9]
• only transferring data that has changed from one frame to the next from the application to the library

Example of coexistence with immediate mode in the same library is OpenGL.^[10] OpenGL has immediate mode functions that can use previously defined server side objects (textures, vertex buffers and index buffers, shaders, etc.) without resending unchanged data.^{[11] [12]}

Examples of retained mode rendering systems include Windows Presentation Foundation, SceneKit on macOS,^[13] and PHIGS.

See also

• Compositing window manager
• Scene graph

Notes and References

1. Book: Jin, Zhefan. 2006 10th International Conference on Computer Supported Cooperative Work in Design . Retained-Mode Parallel Graphics Rendering for Cooperative Design Environments . May 2006. https://ieeexplore.ieee.org/document/4019178?section=abstract. 1–6. 10.1109/CSCWD.2006.253142. 1-4244-0164-X. 5825966.
2. Web site: Retained Mode Versus Immediate Mode. Win32 apps. Quinn Radich. Microsoft. May 30, 2018. 21 December 2019.
3. Web site: stevewhims . Predication queries - Win32 apps . 2022-12-09 . learn.microsoft.com . en-us.
4. Web site: GUI Programming. Alex. Feldmeier. UWP Computer Science and Software Engineering Technical Report. October 12, 2013. 22 December 2019. Retained mode has been the standard for years. Just about every GUI is in retained mode. .
5. Web site: QuinnRadich. Retained Mode Versus Immediate Mode - Win32 apps. 2020-08-21. docs.microsoft.com. en-us.
6. Web site: OpenGL double buffering. 7 May 2020.
7. Web site: DirectX double buffering. 7 May 2020.
8. Web site: OpenGL face culling. 7 May 2020.
9. Web site: DirectX occlusion culling. 7 May 2020.
10. Web site: OpenGL. 4 May 2020.
11. Web site: 2013-08-19. OpenGL Driver Support. 2020-08-21. NVIDIA Developer. en.
12. Web site: 2011-07-19. OpenGL - The Industry's Foundation for High Performance Graphics. 2020-08-21. The Khronos Group. en.
13. Book: Weiher , Marcel . iOS and macOS Performance Tuning: Cocoa, Cocoa Touch, Objective-C, and Swift. Addison-Wesley Professional. Feb 24, 2017. 22 December 2019. SceneKit and SpriteKit on the other hand are retained-mode APIs. 9780133085532.