CAD:Vector Based

The CAD file is a vector based file. That is to say that the items in the file are maintained as entity types (e.g. line, circle, etc) with their coordinates and properties stored in the file as opposed to a pixel map. To view the drawing all entities on visible layers are rendered to a pixel map and rasterized to the monitor.

This approach allows for easy scaling and transformation.

Description

Coordinates are being expressed in drawing units.Drawing units are not expressing particular units(meters,inches etc). In this part user have to make some assumptions in order to define that the coordinates of the drawing mean particular units(meters,inches etc). For example: For a mechanichal drawing we can make the assumption for example: where one drawing unit defines one millimeter(1 D.U=1mm) For a architectural/technical drawing we can make the assumption for example: where one drawing unit defines one meter(1 D.U=1m) This can be very helpfull in designing,dimensioning,retrieving informations from the drawing(distances,area calculations)

Remarks

Bitmap Example

Bitmap files maintain an array of pixels each assigned a color and luminosity.

Consider the following line:

Zoomed In to the pixel level

At the pixel level we see that one pixel is related to, at most, eight other pixels. This is not enough information for us to reliably scale the entire object. At best, we can apply a lossly algorithm to guess at the relationship of one pixel to another. This results in the scaling of pixel maps producing blocky images.

Vector Example

Using the above example we will define an object called Line. We will define its:

• StartPoint = 0,0
• EndPoint = 10,-10
• PenColor = Black

Given this information we then create a pixel map by feeding the object to the render engine.

Scaling the line becomes a simple geometric transformation afterwhich we feed the information back into the render engine to create a new pixel map. Thus eliminating any artifacts or blockiness.