<p>A raster display draws every pixel on the screen in every frame whether there is something to show or not.</p>

<p>A random scan display activates only those pixel which are occupied by an geometric primitive.</p>

<p>So yes, they both use pixels, but the difference is in how they draw the pixels onto the screen.</p>

CC BY-SA 3.0
2016-01-24T14:13:13.327Z
I read that in a raster display a picture is kind-of jaggy but in random we get a smooth line. why and how does this happen when both work on pixel level anyhow?
pratik watwani
CC BY-SA 3.0
2016-01-24T14:36:38.283Z
Both systems produce some aliasing (I think this is what you mean with 'jaggy') on pixel-level since there is only a finite discrete resolution available. I don't know how the amount of aliasing compares, since in the background of a rasterizer geometric primitives also get converted into pixel-grid, and a random scan has to do the same conversion. I can only assume that because a random scan can directly follow the line it is easier to anti-alias.
Dragonseel
CC BY-SA 3.0
2016-01-24T13:51:51.840Z
2016-01-24T13:51:51.840Z
Dragonseel
<p>Raster scan display forms an image with pixel whereas a Random scan display works with Geometric primitives, but even a geometric primitve( a line) is made up of pixels so what is the difference?</p>

<raster-image><display-lists>
How is Raster and Random Scan Display different?
pratik watwani
# How is Raster and Random Scan Display different?

(Asked by: username_0 on 2016-01-24)

Raster scan display forms an image with pixel whereas a Random scan display works with Geometric primitives, but even a geometric primitve( a line) is made up of pixels so what is the difference?

**Tags:** raster-image, display-lists


---

## 1 answers

### Answer by username_1 on 2016-01-24. Score: 1

A raster display draws every pixel on the screen in every frame whether there is something to show or not.

A random scan display activates only those pixel which are occupied by an geometric primitive.

So yes, they both use pixels, but the difference is in how they draw the pixels onto the screen.

> **Comments:**
> **username_0**: I read that in a raster display a picture is kind-of jaggy but in random we get a smooth line. why and how does this happen when both work on pixel level anyhow?  
> **username_1**: Both systems produce some aliasing (I think this is what you mean with 'jaggy') on pixel-level since there is only a finite discrete resolution available. I don't know how the amount of aliasing compares, since in the background of a rasterizer geometric primitives also get converted into pixel-grid, and a random scan has to do the same conversion. I can only assume that because a random scan can directly follow the line it is easier to anti-alias.  

---

