Artifact (computer graphics)

In computer graphics , an artifact is a visible, undesirable display in digital images that does not come from the original data. There are a number of reasons that could be responsible for this misrepresentation. The term "artefact" is also used in digital photography , see artefact (photography) .

Types of artifacts

Left : image with low compression. A moiré pattern can clearly be seen on the left under the lens .
Right : Image with strong JPEG compression. There are visible block artifacts to see.

Rasterization: An unavoidable trigger for graphic artifacts is the rasterization of the precisely defined objects in the two-dimensional integer system of the screen resolution. In all non-trivial cases, information is lost, but the visible impairment can be minimized by antialiasing .
Compression artifacts: With lossy image compression such as JPEG or lossy video compression such as MPEG , visible artifacts (mostly block artifacts ) occur due to lost information. These are unavoidable, but the algorithms try to keep the impairments visible to humans to a minimum.
Rounding errors in graphics cards: In the first generations of graphics cards that could perform 3D calculations, the floating point accuracy of sometimes only 8 bits was the reason for rounding errors, which led to clearly visible artifacts. Today this problem has largely been resolved.
Shader artifacts: Another reason for display errors can be a faulty or overclocked graphics card. If the vertex shader does not work correctly, some of the vertices will not transform properly and are therefore not in the correct position, and the rendered objects will look distorted or "spiky". If the pixel shader does not work properly, the objects are transformed correctly, but the color of at least some pixels is wrong. Graphics chip manufacturers such as AMD or nVidia post utilities on their respective websites to check for such errors.