Coordinate System

Three-dimensional space is conventionally measured with the help of three perpendicular measuring directions known as the X, Y and Z axes.  The point where the axes meet is called the origin.  To locate a point within space requires three measurements called the X, Y and Z coordinates (technically ‘Cartesian Coordinates’).  These are the distances measured along each axis from the origin to arrive at the point.  They are the 3D equivalent of a 2D map reference.  The coordinates of the origin are X = 0, Y = 0, Z = 0.  The units represented by these coordinates are entirely arbitrary and can be changed by Scaling the Project .

L3DD follows the convention set by OpenGL --- the industry-standard 3D graphics software used by L3DD.  This is easily understood with the help of L3DD’s opening screen, showing the house, the ‘groundplane’ and the X, Y and Z axes:  The X and Z axes are horizontal and lie in the groundplane.  The groundplane is like a flat plane on which the house is built.  The X axis emerges through the right side of the house while the Z axis comes out through the front door.  The Y axis sticks straight up in the air through the middle of the roof.  The negative ends of each axis are in the opposite directions --- e.g., straight down like a drill hole into the ground for the negative end of the Y axis.  The XYZ Axes and Groundplane can be turned on and off.

The origin need not be in the middle of the floor.  If you wish, you can select the whole house and move it so that the origin is now situated at the left rear corner of the house.  All house coordinates are now positive.  You can even rotate the house within the axes so the Z axis comes out the roof.  Some CAD programs have the Z axis up in the air.

If the Vertex and Edge Handles are turned on, as they are in the above illustration, we can find some coordinates.  With the left mouse button, click on the deep blue edge handle in the middle of the roof ridge and the Status Bar at the bottom of the L3DD window will display the coordinates X = 0., Y = 77 and Z = 0.  That is, the roof ridge is 77 units above the origin.  If we move right a bit and click on the green vertex handle at the right end of the roof ridge we get the coordinates X = 50, Y = 77, Z = 0.  Now try the green vertex handle where the roof, back wall and right wall meet.  The coordinates here are X = 100, Y = 50, Z = -50.  Note the negative Z coordinate.  If a face is selected the coordinates shown are those of its center point.  The right-hand wall, for example, yields the coordinates X = 100, Y = 25, Z = 0.

For faces, group selections and the whole object, the default coordinates shown in the Status Bar are the median coordinates of all the vertices contained within the selection.  However, these can be changed to several other options with the Coordinate Display command.

Copyright © Ligno3D Systems, 2006