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    Splines are a Snap! Parts 1, 2, and 3

    A gmax® B.A.T. Tutorial Part 1

    Please PM STomnibus if you have any questions about this article.

    Author: Larsz

    Required: gmax®, the Maxis BAT gamepack

    Recomended: Complete the gmax® Tutorials (in order to get familiar with the gmax® user interface)User Level: Beginner

    Using Splines and Snaps together allows the user to create precision objects in gmax®. A Spline object is a very versatile object with many editing tools. Snaps make editing Splines easier. This tutorial explains how to use Splines and Snaps to create simple and compound objects. I would recommend completing the gmax® Tutorials that are available from discreet.com before beginning this tutorial.

    Compound Splines Let's create a compound object made up of edited splines.

    Some setup first. When you Start the B.A.T. you will see 4 Viewports; Top, Front, Left and Perspective.


    I am not sure why the B.A.T. starts zoomed so far out, or maybe it is just the way it starts for me but we want to work with meters and not tiles. To find out the distance between the gridlines, Left Click inside the Front Viewport to make it the active Viewport, and move your mouse to the 0,0,0 Point and then move the mouse to the first gridline to the right. Look at the value in the X Coordinate box. The value in the X Coordinate box indicates distance in meters from the 0,0,0 point. 16 meters is indicated by the first gridline in the picture below.


    Either use the Zoom Tool or scroll your scroll wheel on your mouse up to Zoom In until you see gridlines inside the Major Gridlines.


    We will be working in the Front Viewport to begin with. Make sure the Front Viewport is highlighted, then press the "w" key on your keyboard. "w" is the hotkey to toggle the active viewport from Minimum (4 viewports onscreen) to Maximum (Active viewport onscreen only).

    Front Viewport Maximized


    We are now setup to begin.

    Step 1. Create a Rectangle and an Arc.

    Rectangle Setup


    Make sure the "Grid Points" snap is checked. I usually leave "Vertex" checked as well. To open the "Grid and Snap Settings" dialogue, Right Click the Snap button. To "Turn On" the snap, Hold the Left Mouse button on the Snap button and select "2.5".

    Left Click + Drag the rectangle shape, Right Click to End the Rectangle Creation - I created a 3x3 Rectangle


    Arc Setup


    We are going to create the Arc using the Vertex Snap. Make sure that the Grid Points snap is not checked. The Rectangle shape has 4 Vertices (Vertex plural), one in each corner. We want to create an Arc that caps the Rectangle. To create an Arc shape, Left Click + Hold on the upper left Vertex of the Rectangle. When you hover the cursor near a Vertex you will notice how the Snap works. The Vertex you are near will have a Cross highlight.


    When the upper left Vertex is Snapped (highlighted), Left Click + Drag to the upper right Vertex. When you see the Snap, release the Left Mouse button.


    Your next Left Click will finish the Arc shape. Move your mouse to see how the Arc will change based on the final click. Notice how the Radius Value in the Parameters Roll-Out of the Arc changes as you move your mouse. Create your Arc with a 1.5 Radius like the image below.


    If you can't get the Radius to stop exactly at 1.5, get it as close as you can. Left Click in the Radius entry box and enter 1.5 for a value. As long as you haven't completed the Arc creation you can edit these values. To end the Arc creation, Right Click in the workspace.

    The Rectangle and Arc have to be converted to Editable Splines. Select the Arc, Right Click, Select "Convert To.." and then select "Convert to Editable Spline" You will also have to convert the Rectangle to an Editable Spline using the same procedure. You will be converting a lot of shapes to an Editable Spline as you work with Splines. The only Spline shape that doesn't require conversion is the Line shape.


    A gmax® B.A.T. Tutorial Part 2

    Author: Larsz

    Required: gmax®, the Maxis B.A.T. gamepack

    Recomended: Complete the gmax® Tutorials (in order to get familiar with the gmax® user interface)

    User Level: Beginner

    See http://simtropolis.c...0&enterthread=y for links and the first part of this article

    Step 2. Breaking Stuff

    Select the Rectangle. Left Click the Modify Tab. Left Click the Exand/Collapse Toggle to expand the "Stack" and display the Sub-Objects.


    Troubleshooting - Your object is not an "Editable Spline"

    If you get to this point and your Object window looks like this:


    You have not successfully converted the object to an Editable Spline. Follow the instructions on the first page to convert your objects to Editable Splines.

    Select the "Segment" Sub-Object. A Rectangle object is made up of 4 Segments (Sides). Left Click on the Top Segment of the Rectangle


    Press the Delete Key on your keyboard. Yes, we don't want that Top Segment anymore. While we are here, why don't we make what is left of the rectangle a little taller.

    Snaps not only work when you are creating objects, they also work when you are editing those objects. Select the Vertex Sub-Object. Check the Grid Points Snap. Select the Move Command. Select the Lower Right Vertex of what is left of the Rectangle.


    Move your mouse near the lower right Vertex so that you see the Vertex Highlight. Left Click + Drag the Vertex down. Because the Grid Points Snap is enabled, you can only Move the Vertex by the Grid (or Vertices if there were any others). Drag the Vertex down 3 Grid Points and release the Left Mouse button. You will notice that the Grid Point Snap Highlight is a large (1x1 grid) crosshair.


    Now do the same for the lower left Vertex.


    Left Click Editable Spline to select the Object (we are done working with the Sub-Objects for now). Uncheck the Grid Points snap. We still have 2 separate objects. Later on we are going to want to make this a 3D object. It is currently only a 2D object. In order for the 3D modifiers to work correctly later, we need 1 solid object. Splines can be connected to each other, in fact attached Splines are great for manipulating objects. We want to Attach the Arc and what is left of the Rectangle together.

    Again, make sure that you collapsed all the Sub-Objects and that the Rectangle Editable Spline is selected. You will find the Geometry Roll-Out under the Object/Sub-Object window. You may have to use the Roll-Out Scroll Bar to scroll down. The Scroll Bar is very small and easy to miss. Left Click the Attach Button.


    Now, move your cursor over the Arc. You will see the cursor change to the Attach Cursor.

    AttachCursor.jpg Left Click to Attach the Arc to the Rectangle. Right Click in the workspace to end the Attach operation. The 2 objects have now become 1 object. Let's name the object, Frame. Even though we have attached the two objects, Frame is not a "Closed" Spline. We have to Weld the Vertices where the two objects meet. In order to Weld the Vertices, we have to work with the Vertex Sub-Object of Frame. The Weld command is found in the same Geometry Roll-Out as the Attach command.

    Here is the setup for the Weld.

    WeldSetup.jpg The Weld operation is a 2 step process. The first step is to select the Vertices you wish to Weld. You select the Vertices by Left Click + Drag a selection box around the Vertices.

    The Selection Box


    After releasing the Left Mouse button when selecting


    Step 2 is to Left Click the Weld button. Make sure there is a positive value in the box next to the Weld button. The default value of .1 should work fine. Our objects connect in 2 places, you will have to repeat the Weld operation with the Vertices on the left side where the arc and rectangle meet. Left Click Editable Spline in the Object window to select the object Frame. The object Frame should now be 1 solid object, we can test this using a 3D modifier, Extrude.

    A gmax® B.A.T. Tutorial Part 3

    Author: Larsz

    Required: gmax®, the Maxis B.A.T. gamepack

    Recomended: Complete the gmax® Tutorials (in order to get familiar with the gmax® user interface) User Level: Beginner See http://www.simtropol...0&enterthread=y and http://www.simtropol...4&enterthread=y of this article for links and more information.

    Step 3. Testing the Frame object

    The best analogy I can think of for the Extrude modifier is Play-Doh. Play-Doh makes toys that you put Play-Doh into and by forcing the Play-Doh material through a hole, you create a formed shape. Think of the object "Frame" as the hole that you are going to force 3D material through. By Extruding our 2D object Frame, will will create a 3D formed shape.

    To setup for Extruding, make sure the object Frame is selected, the Modify tab is active and that you are at the Editable Spline level of object Frame.

    Extrude Setup


    Left Click in the Modifier List to expand the list. There are several Modifier Groups, the Extrude Modifer that we are looking for can be found in the Mesh Editing group. Highlight the Extrude modifier and Left Click to apply the modifier.


    After you apply the Extrude modifier, you will see the following screen.


    Make sure that the Cap Start and Cap End settings are checked. To see the Extrude modifier at work, press the "w" key on your keyboard to return to minimized viewport. Left Click inside the Perspective Viewport and zoom in on the Frame object.


    The best way to see the Extrude modifier at work is to Arc Rotate the perspective view. You can use the Arc Rotate tool, or you can hold down the Alt key + Middle Mouse button and move the mouse to change the viewpoint. You will also notice that the Frame object is solid but it is flat. Left Click the spinner up button next to the Amount box to change the thickness of the object.


    If your object matches the above picture, Save your model. After saving, feel free to play around with the extruded object. You can change the Amount, turn the Extrusion modifier On/Off using the "light bulb" toggle or uncheck/check some of the parameters. One of the useful features of creating this object as an Editable Spline is that you can go back into the Editable Spline level of the object or even the Sub-Objects and edit. The Extrude modifier will adjust the extrusion accordingly. When you are done playing, Open your saved model, do not save the changes when prompted.

    If your object does not match the above picture, you can fix the problem without losing your work, another benefit of working with Splines. I will run through a troubleshooting and repair.

    Troubleshooting - Weld FailureIf the Welding of the 2 initial shapes failed, your Extruded object will probably look like this.


    You can leave the Extrude modifier in place and go "down the Object Stack" to the Vertex sub-object level and Weld the vertices just as you did earlier in the Welding operation. After you are done editing, return to the Editable Spline level and then Left Click on the Extrude Modifier to see your changes.

    SummaryAt this point, I would recommend going through the tutorial a couple more times until you can do it from memory. You can create nearly any shape using this technique and the only 3D to worry about is which viewport you are working in. Feel free to experiment with the other Spline shapes like Circle and Star. The other shapes behave the same way when converted to Editable Splines. I will cover "holes" or "openings" in the next part of the tutorial, but if you are up to it, simply create a shape inside the existing shape, convert it to Editable Spline and then Attach it to the existing shape. As long as the hole shape is a closed Editable Spline, completely within another Editable Spline and Attached it should work fine.

    I will also cover all of the Snaps in the first part of the next tutorial, but feel free to experiment with them as well, Endpoint, Midpoint and Perpendicular are very handy when dealing with geometry.

    I am certainly no expert with gmax®, I learned the hard way, trial and error. I think it is important that you get real comfortable with working in the Object Stack and understand how it works. When I first started playing with gmax®, I usually just deleted objects and started over when they were not right because I didn't understand how dynamically the Object Stack works. I was also accustomed to working with Autocad and it's set of Snaps and it took awhile for me to get used to snaps in gmax®. It is also important to realize that for most people, including myself, you will have to do things many times in order to understand how things work. Please make sure you understand the concepts in this first tutorial before continuing onto the next part.

    Here is a window frame I created with Editable Splines.


    ** Note ** If you are going to try to Export this model using the B.A.T. Export, make sure that you move the model up so that the entire model is above the Y plane.

    If you have any questions about this article, please PM STomnibus.

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