Antialiasing Technique

Antialiasing methods were developed to combat the effects of aliasing.
There are three main classes of antialiasing algorithms.


As aliasing problem is due to low resolution, one easy solution is to increase the resolution , causing sample points to occur more frequently. This increases the cost of image production.


The image is created at high resolution and then digitally filtered. This method is called supersampling or postfiltering and eliminates high frequencies which are the source of aliases.


The image can be calculated by considering the intensities over a particular region. This is called prefiltering.

Prefiltering.


Prefiltering methods treat a pixel as an area, and compute pixel color based on the overlap of the scene's objects with a pixel's area. These techniques compute the shades of gray based on how much of a pixel's area is covered by a object.
For example, a modification to Bresenham's algorithm was developed by Pitteway and Watkinson. In this algorithm, each pixel is given an intensity depending on the area of overlap of the pixel and the line. So, due to the blurring effect along the line edges, the effect of antialiasing is not very prominent, although it still exists.
Prefiltering thus amounts to sampling the shape of the object very densely within a pixel region. For shapes other than polygons, this can be very computationally intensive.

Supersampling or postfiltering is the process by which aliasing effects in graphics are reduced by increasing the frequency of the sampling grid and then averaging the results down. This process means calculating a virtual image at a higher spatial resolution than the frame store resolution and then averaging down to the final resolution. It is called postfiltering as the filtering is carried out after sampling.

The drawback is that there is a technical and economic limit for increasing the resolution of the virtual image.


Since the frequency of images can extend to infinity, it just reduces aliasing by raising the Nyquist limit - shift the effect of the frequency spectrum.
Supersampling is basically a three stage process.

A continuous image I(x,y) is sampled at n times the final resolution. The image is calculated at n times the frame resolution. This is a virtual image.

The virtual image is then lowpass filtered

The filtered image is then resampled at the final frame resolution.
Buy me a Cup of Coffee

MONIKA YADAV (MCA),
Software Engineer,
www.NotesGuru.in, Indore

ROHIT KESHRIYA (MCA),
Software Engineer,
www.NotesGuru.in, Indore

For guest faculty Contact us on following E-mail ID:

monikay.aerosoft@gmail.com
monikay.aerosoft@rediffmail.com
monikay.aerosoft@yahoo.com
monikay.aerosoft@hotmail.com
rohit.aerosoft@gmail.com
rohit.aerosoft@rediffmail.com
rohit.aerosoft@yahoo.com
rohit.aerosoft@hotmail.com

Note: We have been used search engines for gathering content.