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What is CGI

CGI means Computer Generated Imagery - i.e. images generated by the computer. With this article we want to explain the process of creating a CGI.

Topics covered in this blog:

  • CAD
  • DCC
  • CGI
  • Production / Workflow
  • Work of a 3D-Artist
  • Data preparation / scene tree
  • Backgrounds / Environments
  • 3D rendering
  • Animation

The basis of such images is always 3D data. These can come from a CAD system or can be specially modelled or constructed. Since nowadays almost every manufacturing company has 3D data of its products, it is now common practice in most cases to work with CAD data that are exported. Some common CAD programs are for example CATIA, Pro-E, PTC CREO, Rhino, Solidworks, and many others (a good summary of most CAD programs can be found in this list of CAD programs on Wikipedia). If you do not have CAD data, 3D data must be modeled. This is not a problem, but is usually quite complex. Often small, secondary objects have to be modelled for the background, because the customer usually only has CAD data of his product and the scene gains life and credibility through the objects in the background. However, the normal case is CAD data for visualization, which is why we limit ourselves in this article to the production of images based on CAD data. If you want to know in detail what has to be done with CAD data and when modelling makes more sense, read our BLOG article about "CAD data or modelling".

As a supplement it should be mentioned that CGI and product photography have a lot in common. But there are a few essential differences that justify the use of CGI in relation to photography. In our BLOG article "CGI and photography" you can learn more about this topic.

Let's take a look at the workflow of a CGI production: The CAD data must be converted into a different format for this purpose so that the Digital Content Creation Software (DCC) can handle the data. DCC software is the term used to describe those programs with which multimedia content can be created. Well-known DCC applications in the field of 3D are for example Maya, 3DsMAX, Blender, Houdini, Cinema4D and a handful of others, which you can have a look at here. Even the big Hollywood effects studios use these "standard 3D programs" to create the effects for their blockbuster movies; this is called VFX, short for "visual effects". But let's stay with creating multimedia content like images and animations. Once the data from the CAD program has been transferred to the 3D content software, the work of the CG artist begins (this is the job title of people who work with DCC programs).

 

Screenshot of a CAD program (Catia) - Source: www.encad-consulting.de/produkte/plm/catia/catia-v5/jig-and-tooling-creation-jte/

One of the first tasks is to sort the data. Since the CAD design has different goals than the visualization, the data must be restructured. The so-called scene tree reflects the structure and hierarchy of the data record. When it is sorted, the objects are assigned materials.

Since the objects of the CAD data are usually assigned many different colors in order to be able to distinguish between them in the design, the objects must be assigned material properties in the DCC software. These are, for example, color, reflection, transparency, etc. Depending on the complexity of the product, this can take several hours or even days.

Assigning materials from the material editor to the objects of the 3D scene

Once the so-called shading is complete, the scene is set up with camera and lights. This works similar to a real photo studio. You place a camera and set up the lights so that the product looks exciting and all shapes and contours are clearly displayed.

Setting up the camera with background and backplate

If the background of the image is a backplate, as in our image example, the camera must be adapted to this backplate. Usually, certain camera parameters are already fixed during the photography of the environment, which are passed on to the 3D artist so that he gets the virtual camera congruent with the real camera. You can read here what you have to pay attention to when photographing the environment for CGI and how to get the background into the 3D program.

With this step the work of the 3D-Artist is almost finished. He only has to convert the 3D scene into a 2D image. This work step is called rendering - calculation. Such a 3D rendering can take a few hours, depending on the resolution and size of the data. You can read more about rendering in our Technology Workshop "3D Content Creation".

After the image has been calculated, the work of the 3D artist is usually done. The image is handed over to the compositing artist, who gives the final touch to the image using a 2D program such as Photoshop. It is possible to render layers from the 3D program, which helps the compositing artist to draw masks and make color corrections more easily. Normally he deals with the brightness of the image and makes color corrections where necessary.

At the end the created image is handed over to the customer, who can use it in many ways. As an image on the website, in print media or for posters at trade fairs. The so-called Computer Generated Image, CGI for short, is now complete.

If you go one step further, other media can be developed to complement this workflow. An animation on the basis of this processed data can breathe life into the product or the data can be used for augmented and virtual reality applications. Once the data is available, it can be used in many channels. However, BEFORE the data is processed, it is necessary to consider the media in which the data will be used. Otherwise you will create unnecessary additional work, which could be saved with good planning.

In our REPORT "3D Content Creation" (german) you will learn in detail how to produce a CGI and which layers are used to create it.

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