What is cgi? Beyond the knowledge

The Basics What is CGI? And what does rendering mean?

Computer Generated Imagery (CGI): The term CGI stands for digital images and animations generated by 3D computer graphics. The term 3D graphics is used synonymously for the CGI image. The process first found practical application in film production/ cinematography, computer simulation, and for creating visual special effects. Characters and entire worlds were brought to life in well-known films such as Star wars, Lord of the Rings or Avatar, through CGI.

In addition to these areas, CGI is used by LIGHTSHAPE, among others, for product visualization and advertising, so in the following we will also concentrate on this focus - our area of expertise. For consumer goods and many industries, the uses of CGI are very diverse. As an image on the website, in print media or for posters at trade fairs, the use of CGI is conceivable in all media, digital or analog.

In addition, other media can be developed. An animation based on the data prepared for the CGI can breathe life into the product. Playing out the data for augmented and virtual reality applications is also possible. Once the data is available, it can be used in many channels.

Rendering (3D rendering): Rendering is the process of calculating images on a computer using special 3D software. To do this, a 3D artist creates a 3D scene based on raw data with camera, lighting and materiality of all objects. The term rendering is also used as a synonym for an image that has been created in the computer.

Strictly speaking, everything you see on a computer screen is rendered. So also the display of web pages, the user interface of the operating system, etc.

Comparison CGI vs. Photography

The limits of photography

A photograph is usually easier to take than creating an image with a computer using 3D data. However, there are some cases where photography reaches its limits or can be as costly as a CG production. Have you ever tried to photograph a machine that is 8m or higher? You will need a very large studio for that.

Alternatively, they show the machine on location. But is there the necessary space for the photographer there? Is that the context and background you envision, or are there things in the picture you don't want to see? These general conditions severely limit classic photography. Afterwards, the photo would need to be post-processed. Depending on how many things need to be retouched, this can be very time consuming and expensive.

Macro photography

What can be difficult to photograph on a large scale is sometimes impossible to photograph on a small scale. You can use the virtual camera to fly into small components, bring out the inner workings, and even show this in motion. Camera settings that would be impossible to achieve with a conventional camera can be perfectly staged and processes, no matter how small, can be communicated in a comprehensible way. Macro shots take on a whole new meaning because there are no limits to imagination and physics.

Of course, what works well in the macro world also makes sense on a larger scale. For example, you don't need elaborate camera slides or cranes to realize settings or film driving situations.

Prototype illustration

Another elaborate case of photography is photographing prototypes. Prototypes are never quite finished, have the wrong configuration, or require elaborate emotional staging. In the case of a new vehicle, marketing materials need to be developed well in advance of the sales launch. To accomplish this, the prototype must be transported to a special location, set up and photographed. The whole thing then also under secrecy, because one does not want to see the vehicle published prematurely.

With CG technology it is possible to photograph the location and the lighting conditions on site in order to visualize the data set of the virtual 3D vehicle afterwards on the computer with the lighting and reflection photographed on site.

Individual consideration

Nevertheless, there are still reasons to photograph products classically. The customer must weigh up how high the cost/benefit factor is for classic photography. A simple photo without much preparation is easy to take. But does this photo live up to the visual claim? Is it worth doing elaborate photo shoots where half of it has to be retouched in the end? In contrast, with CGI everything is possible and you can quickly see what the end result will look like.

But: both ways have their specific advantages and disadvantages. In which cases one or the other approach makes more sense must be decided on a case-by-case basis.

Initial situation

CAD data

The basis of such images is always 3D data. These can come from a CAD system or be specially modeled or constructed. Since nowadays almost every manufacturing company has 3D data of its products, it is now common in most cases to work with CAD data that are exported. Some common CAD programs are for example: CATIA, Pro-E, PTC CREO, Rhino and Solidworks.

If you don't have CAD data, you have to model 3D data. This is not a problem, but it is usually quite time-consuming. The normal case, however, is CAD data that are prepared for visualization.

Missing CAD data

Modeling

When do 3D models have to be created by hand? Doesn't the CAD user also model? He does, but very precisely, because he constructs models that are dimensionally accurate and contain a lot of meta information. The 3D modeling we are talking about here comes from the film and games industry. Here you are dealing with "objects" of which there is no construction data. Plants, animals and people - mostly soft and organic objects.

In which technical development areas does modeling have to be used? In the design phase in architecture, one can resort to technology. CAD software can represent machine parts perfectly, but organic forms are very difficult to represent. In automotive design, for example, almost everything can be designed in CAD, except for soft components like the seats. Upholstery, unevenness of leather and seams have to be modeled. When machines interact with organic objects, such as a tractor with a field, modeling is essential.

There is one more special case where 3D modeling is essential. Interactive applications for mobile devices or the Internet. CAD models are much too large for this purpose and cannot be processed by mobile devices. They have to be remodeled in a simplified way.

Typical programs

Digital Content Creation Software (DCC)

Let's deal with the workflow of a CGI production: The CAD data must be converted into another format for this, so that the Digital Content Creation Software (DCC) can handle the data. DCC software refers to those programs that can be used to create digital content. Known DCC applications in the field of 3D are for example Maya, 3DsMAX, Blender, Houdini, Cinema4D and a handful of others. Even the big Hollywood studios use these "standard 3D programs" to create the effects for their blockbuster movies, this is called VFX, short for "Visual Effects".

The work of a CG Artist

Once the data from the CAD program has been transferred to the 3D content software, the CGI artist's work begins. CGI artists (also called 3D artists) create CGIs for all conceivable media. One of the first tasks is sorting the data. Since CAD design has different goals than visualization, the data must be restructured. The scene tree reflects the structure and hierarchy of the data set.

Once this 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 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. Once the so-called shading is complete, the scene is set up with camera and lights. Since 3D programs are set up like a real photo studio, cameras need to be set up and lights need to be set. This works similar to a real photo studio.

You place a camera and adjust the lights so that the product is exciting perspective to see and the shape and contours are optimally worked out.

If the background of the image is a backplate, the camera must be adjusted to this backplate. Usually, when photographing the environment, certain camera parameters are already specified, which are passed on to the 3D artist, so that he gets the virtual camera congruent with the real photographed background.

With these steps, the 3D artist's work is almost complete. He only has to convert the 3D scene into a 2D image. Rendering, as described above, can take a few hours. Depending on the image size and complexity of the content. Light distribution, transparency, refraction, shadows, correct reflections are calculated with highly complex mathematical methods to calculate the color of each pixel.

Real environment

The background

There are several ways to add backgrounds to products. The simplest one is the white background. The product is rendered with a white background. As simple as this is, it can look boring.

A more advanced measure is to integrate a floor or a room border. This immediately gives you a more realistic understanding of the placement of the object. Reflection on the floor gives more depth and makes the image easier to read. However, the image does not yet have a background. To develop this is a bit more complex.

There is the possibility to model a virtual background to make the product appear in a clean, reduced environment. However, this is not yet photorealistic.

For a photorealistic picture in a real environment, two more pictures have to be taken. The desired background or location is photographed. The backplate. To capture the local light situation and use it in the 3D software, a photo with a high dynamic range of light (HDRI) is taken with a 360° camera. which is used to illuminate the scene in the 3D program. If digital objects, real captured background with lighting situation are perfectly matched, you get a photorealistic image as if it was created on site with real objects.

Final editing

Compositing Artist

The last step is to assemble the individual image layers into the final image. The image is handed over to the compositing artist, who puts the final touches on the image using a 2D program such as Photoshop. The 3D program gives you the option to render the image not as a whole, but in separate parts or layers. Objects can be separated, but also highlights, shadows, reflections and depth information. This gives the compositing artist maximum freedom in image retouching and composition.

A good compositing artist can create a highly emotional image from a rather sober rendering. In the image editing programs, some effects can be recreated relatively quickly that would take an extremely long time if they were rendered. E.g. motion blur, light effects, aperture spots, etc.

The CGI is ready and can be used like any photo in any media and application.

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