Introduction

In this tutorial, you'll learn how to create paths and attach objects to them in TGB. A path is a series of points called 'nodes' that are connected together by various means. The level builder provides a tool with which paths can be created and edited, and objects can be attached. The path object in TGB (t2dPath) is a scene object itself, so it can do things like have velocities applied, react to physics, and even attach to another path.

For this tutorial, we will be using the Torque Game Builder project called TutorialBase. So, run Torque Game Builder, and if the project is not already loaded, select Open Project from the File menu, then select TutorialBase/project.t2proj from the list and press OK. Also, if you had previously created a level with this project it will be loaded. In this case, select New LevelNew Level from the File menu.

Creating a Path

Select the create tab in the side panel, scroll down to the Other rollout, and click and drag the GarageGames logo labeled Path into your scene (as shown in Figure 1).

Figure 1

Visibly, it won't seem like much happened, but what you just did was activate the path tool. The path tool allows you to create, move, and delete path nodes. To create a node, simply click somewhere in the scene. To move any of these nodes, you can click on them and drag the mouse. To delete a node, right click on it. You will notice that the path nodes follow the snap settings of the editor just like sizing and moving object. To turn off Snap to Grid you can go to the Level Editor tab in the Edit -> Preferences -> Scene Editor menu and uncheck Snap to X Axis and Snap to Y Axis.

Create a path with four nodes. When you have finished, press Enter on the keyboard or click on the arrow (labeled Selection Tool) in the toolbar. It's very important to note that creating a path with 0 nodes could result in bugs or a crash. Here is the path I created (as shown in Figure 2):

Figure 2

Attaching an Object

Now, create an object by dragging an image from the Static Sprite rollout in the object library onto the scene. I used the GarageGames logo. With your mouse hovered over the newly created object, 5 widgets will appear above it. Select the one labeled Mount this object to another object (as shown in Figure 3).

Figure 3

The object will now be attached to your mouse, following it wherever you drag it. If the mouse gets near a path node, the object will snap to it. When this happens, you can click the left mouse button, and the object will attach itself to the path with the default settings (as shown in Figure 4).

Figure 4

Now, select Save As... from the File menu, enter a filename for your level, and press save. Then, select Run Game from the Project menu. You should see a black screen with the GarageGames logo moving automatically along the path you created. Of course, it's moving kind of slow, and possibly not in the direction you want it to. Luckily, there are several parameters you can configure specifically for pathed objects.

Editing the Pathed Object

Make sure the GarageGames logo object is selected, then click on the Edit tab in the side panel. Scroll down to the section titled Pathing and click on it to expand the rollout (as shown in Figure 5).

Figure 5

Here is a brief description of the purpose of each of the fields.

• Start Node – The start node is the node in the path that the object will start at. Click the left and right buttons and the pathed object will move to the corresponding node on the path.

• End Node – The end node defines the end of the path for this object. This is the node at which the object will stop after it has completed the specified number of loops, or at which it will perform its Follow Mode action in Reverse or Restart mode. This option has no effect if Wrap is selected as the Follow Mode and -1 is selected for Loops.

• Speed – This is the speed at which the object will follow the path in world units per second.

• Move Forward – Unchecking this box will reverse the direction that the object travels around the path.

• Orient To Path – Selecting this option will cause the object to rotate itself depending on the direction it is traveling.

• Rotation Offset – The rotation offset only affects objects that have Orient to Path selected. With a rotation offset of 0, the top of the objects will be facing toward the direction they are moving. Changing this allows you to specify the exact rotation at which the object should orient itself.

• Loops – This specifies the number of times the object will travel around the path. The default value of -1 specifies an infinite number of loops. When the number of loops has been reached, the object will stop at the end node.

• Follow Mode – The follow mode tells the path what to do with the object when it reaches the end node. It comes in three flavors. In Wrap mode, the object will continue in the same direction around the path. In Reverse mode, the object will change its direction and the start node will become the end node. In Restart mode, the object will warp back to the start node upon reaching the end node.

All of these options are applied specifically to the pathed object, not the path itself. So, if you had several objects attached to the same path, they could all configure themselves differently.

Editing the Path

Paths can be edited after creation. To do this, select the path and click on the widget labeled Edit this path (as shown in Figure 6).

Figure 6

This will reactivate the path tool, allowing you to create, edit, or delete nodes. Paths also allow you to specify the method they use to interpolate between nodes. There are four options available that can be selected in the Path rollout of the Edit tab in the side panel (as shown in Figure 7).

Figure 7

Here is the description of each of these types:

• Linear – This is the default and simply has an object move in a straight line from node to node.

• Bezier – The bezier method uses cubic bezier splines to create a curved interpolation between each node. Each node is guaranteed to be a part of the path. Bezier paths have two additional parameters, Rotation and Weight. These parameters can be edited in the path tool when bezier is selected as the Path Type by clicking and dragging the handles around each node (as shown in Figure 8).

Figure 8

• Catmull – The Catmull type uses Catmull-Rom splines to interpolate between nodes. This method requires no extra tweaking and automatically generates a smoothly curved path that goes through each node.

• Custom – The custom method does not actually move any of the objects automatically. Instead, it executes a callback that can be defined in script to move the object. This would be useful in cases where you have a path for an enemy to follow, but you don't want it to follow it directly. This way, the enemy could still obey things like collision and gravity, but still have an easy to define and follow path. The callback looks like this:

function t2dPath::onUpdatePath(%this, %object, %from, %to)

{

// %this is the path object.

// %object is the object following the path.

// %from is the position of the most recently passed node.

// %to is the position of the node being moved toward.

}

Conclusion

This tutorial has covered all the features of the TGB path object. The best way to figure out the effect these features have on pathed objects is to experiment. Paths can be useful for certain game types and menu screens, but their coolest effect comes from combining them with particle effects to make screen saver looking levels. Try it out!