Rendering – the final step in image and video pro­cessing

From design and pho­to­graphy to film tech­no­logy – there is no getting around rendering when digitally pro­cessing objects, images and films. Rendering is es­pe­cially important in graphics pro­duc­tion, image and video editing. It is the final, key step before com­ple­tion, during which a file is trans­formed into a finished image or video.

The reason for this is that the objects you work on are first stored in a com­pressed file format to make them quicker and easier to edit. Specific image prop­er­ties – like colour gradients, shading, depth of field and more – are only added right at the end. This step is called rendering.

Put simply, rendering refers to the con­ver­sion of pre-pro­grammed or recorded datasets into two or three-di­men­sion­al images. During an intensive com­pu­ta­tion­al process, specific prop­er­ties are conferred to the raw data. The result is an image format dis­play­able on computers and other digital devices, which is re­pro­duced with all defined spe­cific­a­tions.

Depending on how detailed the data describes the sub­sequent image, rendering can take a con­sid­er­able amount of time. Moreover, it demands peak per­form­ance from the computer. Par­tic­u­larly in the case of video editing, which involves not just a single image but a whole sequence of images, rendering is a time-consuming process. The higher the per­form­ance of the computer or in­di­vidu­al com­pon­ents like the CPU or the graphics card, the less time it takes.

What exactly happens during rendering depends on whether a digital object, a photo or a video is rendered. For this reason, it makes sense to answer the question “What is rendering?” sep­ar­ately for each of these areas.

When creating a film or video sequence, the various layers such as image, audio, text or graphics are first processed in­di­vidu­ally. After that, the overall com­pos­i­tion is produced in a video editing program by aligning the in­di­vidu­al tracks with each other using a time axis. During the final step of video rendering, all of these in­di­vidu­al files are merged into a single playable video file. This reduces the file size sig­ni­fic­antly, saving heaps of memory and allowing the file to be played on most playback devices.

The pro­fes­sion­al editing of digital photos is a similar process to that of videos. However, instead of in­di­vidu­al tracks, various layers are used by the image editing program which each represent a certain layer of the image. In simple terms, the back­ground, sur­round­ings and focal object are typical layers of an image. Rendering is also the final pro­duc­tion step for images. The in­di­vidu­al image layers are merged to create an overall picture saved as a single image file.

Digital objects and models are primarily used in design, animation, ar­chi­tec­ture, and con­struc­tion – wherever detailed and realistic rep­res­ent­a­tions are required to visualise an idea. In this case, the raw data concerns de­scrip­tions of objects and scenes composed in a markup language like HTML, XML or SVG. These de­scrip­tions specify both the purely geometric ap­pear­ance of the object as well as para­met­ers regarding surface struc­tures, colours, per­spect­ives, light sources, and more. Based on this in­form­a­tion, the final object is created using a special rendering program. Here too, the raw data is processed in this way to reduce the re­quire­ments on computer memory and per­form­ance.