Generative Components 101
Lesson 1: Getting Started
Yikes, where do I start? Lets start by creating a drawing using the seedGC.dgn to use every time you use GC. When you open the dr
awing the GC dialog box will appear and no windows will be open on your screen. Lets start with a new Script File. Go to File>New Script File or use the New Script File tool. The Creating new script file dialog tells us that all features will be deleted from the current graph. This is ok! Don’t worry about ticking any extra boxes at this stage. Click ok. Glossary: Script. A script is typical of programming tools. A script is executed “one time” and populates a model with elements or components. To change the result or create a new file, all the generated elements or components have to be deleted (hence the dialog at left) and the script is re-run with different input parameters.
Your new GC dialog box will change slightly and now include the Script Player Bar, Script Editor tool and Tabs. Two windows also open – a Default-top view and a Symbolic-top view. The symbolic view will show our drawing path in a symbolic graph. You will see in the Symbolic view the Coordinate System / Base CS symbol, and in the other view its GC graphic.
Glossary: Coordinate System. The coordinate system controls the direction of the x, y and z coordinates. When you start a new script you are automatically assigned a coordinate system called BaseCS and it sits “AtModelOrigin”. Rotate your default view and you will see it more clearly. The red line is X, the green Y and the cyan is Z. The active plane is defined by the yellow square. To begin with it sits on the XY plane. You can change the plane to the YZ plane or XZ plane in the GC dialog. Change the plane in the GC dialog and watch the yellow square rotate to the assigned plane.
Ok, I’m ready to draw a line! First we need to place some points that define the line. In GC we always store the relationship between the points and the line and always recomputed the line from the current value of the points. Find the Point tool and place two points in space. Anywhere. You will notice your Symbolic diagram has recorded your moves and has drawn two point symbols.
Now we can create the line or “Feature”. Glossary: Feature. A feature is the name used to constructions. These can be general such as lines, solids. In turn what you build can form the basis of Components” – a box, a wall, column and so on. The you make will be loaded every time you open GC. describe different geometric arc, curves or surfaces and new features or “Generative Generative Components that
Find the Create Feature tool.
A Feature list will appear. Scroll down to Line. Expand the tree and you can see the many methods by which you can create lines. You are creating your line By Points. Expand the tree again to see the parameters that we have to input. Click on StartPoint and a small dialog will appear. Now hold down the CTRL key and hover your cursor over the first point. It will appear purple and the point name will appear in the small dialog automatically. Data point or press return on the keyboard to accept.
The dialog box automatically jumps to EndPoint. Again hold down the CTRL key and hover over the second point. The name of the second point enters the dialog. Data point or return to select. The dialog disappears but no line has appeared. Click on the Apply button at the bottom of the GC dialog and your line will appear.
Notice at the bottom of the dialog the” Name of the new feature”. It has automatically called your new line line0001. You can change this to be your own naming convention if you wish. Notice also the Next button. If you are drawing multiple lines (remember you have to place the points first) then clicking the next button will change the name of the new feature to line0002 and you can go back to the StartPoint to locate your new points. Change the bottom tab to go back to Script file. Click on the Settings [STARTUP] line. Your points and line disappear. You will notice a new line appears beneath “Graph Changed By User”, Click this so the tick appears – you have turned on your change and the points and line reappear (You can also do this by clicking on the Play button). You can edit the name of this change by right clicking on “Graph Changed
By User” and choosing Edit Description. Lets call it Line by 2 points. Now lets save our script file. Click the Save tool. You need to save your script file as a .gcs (generative component script) file. What if I want to delete my line? There are several methods for getting rid of your line. The first is the Delete tool. Just hover over the line and data point to delete. You could also delete the line symbol in the Symbolic Graph! How do I create a T Value Point? Glossary: T Value Point. A T Value Point denotes a relative position - controlled by parameter value (T) in the range 0.0 to 1.0, along a Line or Curve. It is created by the feature: Point> ByParamterAlongCurve. Click the Create Feature tool. You want to place a Point on your line ByParamterAlongCurve (yes, even though you are placing it on a line and not a curve.) Click on Curve and a small dialog will appear. Now hold down the CTRL key and hover your cursor over the line (or curve or bspline etc). It will appear purple and the line name will appear in the small dialog automatically. Data point or press return on the keyboard to accept. The dialog box automatically goes to the next input T:double. Put in the value 0.5. This means that your point will always be in the center of your line.
Hit the Apply button and a yellow point will appear in the middle of your line. Placing the value 0 would place a point at the beginning of the line, 1.0 at the end of the line, 0.2 at 0.2 from the beginning of the line and so on. Notice on the Symbology Graph that the point is directly associated to the Line. What did the “double” mean in T:double? Glossary: Double. A double is another name for a Real number (i.e. any number with a decimal fraction 1.0, 0.5, 0.03 101.9). Integer. An Integer (referred to as int) is any whole number e.g. 1, 2, 101.
What about editing the line or point? Find the edit Feature tool. Hover over your line (or point) and data point to select it. You could also hover over the symbol in the Symbology Graph.
Choose to edit the T point. Lets change the parameter from 0.5 to 0.3 (just click on T:double()=0.5 to edit the number). Don’t forget to hit Apply.
What’s with the difference in the text colours? The Black colour means you have fill in this field. The Blue colour means that you have an option to fill in the field now or in the future. The Grey text stands as additional parameters describing your feature. You cannot access these additional parameters. So for example in the picture above, the T Value is 0.5. The X and Y, Grey parameters, are describing its position. What about normal methods of editing such as move? If you wish to move a point then use the Move tool and move the Points. Create a new script file and draw 2 points and a line ByPoints between them. Use the Move tool to move one of the points. You will notice that the direction of moving your point is dependant on where you selected the point. The line is dependant on the point, which is dependant on the location of the BaseCS (Base coordinate System) - so when you change one feature, all the other features which are linked to that feature, on a higher level of hierarchy, would update accordingly.
If you selected the red line or X direction (The red line is X, the green Y and the cyan is Z), you are only able to move the point in the X direction.
If you selected the green line or Y direction, you are only able to move the point in the Y direction. And in the same manner the blue line moves the point in the Z direction.
If you selected one of the corner selectors you can move your point in any direction.