Materials and the Paint Bucket tool

We will take a quick look here at co-ordinate systems and axis, as it applies specifically to SketchUp. This section is meant only for beginners who do not remember much of their high school mathematics.

When attempting to describe real world objects we can use dimensions. We can define a block of wood by its width, length and height too.

But just defining its 3 dimensions does not tell us anything about its location, its relationship in space to other objects around it. For instance what if we have another block of wood lying close to the first block. Simply defining its dimensions does not tell us anything about how it relates to the first block. We need a way to define where it exists in space, with reference to the first block. We need a base point of reference. Which is exactly what a co-ordinate system is.

A co-ordinate system consists of perpendicular reference lines called axis. We define the location of a point (also called a vertex in some 3D programs) by the distance of the point to each axis. If you are locating objects on a flat surface just two co-ordinates are enough. For instance on a map of the world you can specify the location of any point using a latitude and longitude. This system for locating points on a map is a co-ordinate system, with the axis at the Equator and GMT longitude.

In 3 dimensional space we need a co-ordinate system with three axis. A single point in this space is defined by its distance from the 3 axis, usually called the x, y and z axis. When you open up SketchUp, its default view is called a perspective view. In this view you can view all the 3 axis, which are color coded. The horizontal or x axis is shown in red, the vertical or y axis is shown in green, and the z axis which extends perpendicular to both the x and y axis is shown in blue. You will notice that the lines are solid in one direction and dotted in the other. This indicates the positive and negative co-ordinates. The point where all three axis lines meet is called the origin. For the horizontal x axis all points to the right are positive (the solid line), and all points to the left are negative (shown by the dotted line). Similarly for the z axis the solid blue line indicates the positive direction while the dotted line indicates a negative direction.