In [[computer graphics]], '''image order''' [[algorithms]] iterate over the [[pixel]]s in the image to be produced, rather than the elements in the scene to be [[Rendering (computer graphics)|rendered]].<ref name="Bankman2008">{{cite book|author=Isaac Bankman|title=Handbook of Medical Image Processing and Analysis|url=https://books.google.com/books?id=AnRPBKb7qHUC&pg=PA789&dqq=%22image22object+order%22+rendering&hl=en&sa=X&ved=0ahUKEwi3xeqtmOXiAhVlmK0KHck4CyAQ6AEIMDAB#v=snippet&q=%22object%20order%22%20OR%20OR+%22image%20order+order%22&fpg=falsePA789|date=24 December 2008|publisher=Elsevier|isbn=978-0-08-055914-8|pages=789–}}</ref><ref name="Gross2007">{{cite book|author=Markus Gross, Hanspeter Pfister|title=Point-Based Graphics|url=https://books.google.com/books?id=9LCQ86u9Sc4C|date=2007|publisher=Elsevier|isbn=9780123706041|pages=525–}}</ref> '''Object order''' algorithms are those that iterate over the elements in the scene to be rendered, rather than the pixels in the image to be produced. For typical rendering applications, the scene contains many fewer elements (e.g. [[geometric primitive]]s) than image pixels. In those cases, object order algorithms are usually most efficient (e.g. [[Rasterisation|scan conversion]] or [[Volume rendering#Shear warp|shear warp]]). But when the scene complexity exceeds that of the image, such as is the case often in [[volume rendering]], then image order algorithms (e.g., [[Ray tracing (graphics)|ray casting]]) may be more efficient.
