---
title: "Staircase (aliasing) effect"
subject: "Computer Graphics"
chapter: 2
key: "semester_5/computer_graphics:staircase-effect"
source: https://www.bctengineer.com/q/semester_5/computer_graphics/staircase-effect
site: BCT Engineering
---

# Staircase (aliasing) effect

Computer Graphics · Chapter 2: Scan-Conversion

- Asked in: 2069 Asar, 2 marks
- Video: [Anti Aliasing in Computer Graphics | Stair Case effect | Jaggies Effect | aliasing effect](https://www.youtube.com/watch?v=C_yh7gw7tbg) — SH Academy
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/computer_graphics/staircase-effect
- Whole chapter: https://www.bctengineer.com/md/semester_5/computer_graphics/chapter-2

## Question

What is a staircase effect?

## Short answer

Staircase effect, or jaggies, is the stair-step appearance of slanted lines and curves on raster displays because discrete pixels approximate continuous shapes. It is a form of aliasing, most visible at low resolution, and reduced by higher resolution or anti-aliasing techniques.

## Answer

The **staircase effect** (jaggies) is the stair-step appearance of lines, curves and edges drawn on a raster display. Because the screen consists of discrete pixels, a slanted line or curve can only be approximated by pixels at integer positions, so it looks like steps instead of a smooth line.

```text
Ideal line:        Displayed:
       /                  ##
      /                 ##
     /                ##
```

It is a form of **aliasing**. It is most visible on low-resolution screens and for lines that are nearly horizontal or vertical. It is reduced by increasing the resolution or by anti-aliasing techniques such as supersampling, area sampling and pixel phasing.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. The staircase effect refers to:
   A. stair-step (jagged) appearance of lines and edges on a raster display
   B. flickering of the display
   C. colour banding
   D. loss of lines when zoomed out
   Answer: A. It is also called jaggies. (Key point: Meaning)

2. Why does it occur?
   A. The monitor refresh rate is too low
   B. Lines are stored in floating point
   C. The screen is made of discrete pixels, so slanted lines are approximated at integer positions
   D. Clipping removes pixels
   Answer: C. Only integer pixel positions exist, so a smooth slanted line must be approximated by steps. (Key point: Cause)

3. Which method reduces the staircase effect?
   A. Using DDA instead of Bresenham
   B. Anti-aliasing such as supersampling or higher resolution
   C. Reducing the number of colours
   D. Turning on clipping
   Answer: B. Staircase is aliasing; anti-aliasing and higher resolution make steps less visible. (Key point: Reducing it)

## Related in other subjects

- [Sampling theorem; aliasing and aperture effect remedies](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Asampling-theorem-aliasing-aperture-remedy) — Communication Systems, chapter 4
- [Prove sampling theorem; aliasing and aperture effect](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Asampling-prove-aliasing-aperture) — Communication Systems, chapter 4
- [Aliasing effect and how to minimize it](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Aaliasing-minimize) — Communication Systems, chapter 4
- [Prove sampling theorem; aliasing effect](https://www.bctengineer.com/question.md?key=semester_4%2Fsignals_and_systems%3Aprove-sampling-theorem-aliasing) — Signals and Systems, chapter 4