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Computing Science 10 IB
Transcript of Computing Science 10 IB
1. How to use the Grid function 2. How to use paths Paths and Grids
By Connor, Dalen and Ryan
To create a path, select choose path from the resources menu This screen should pop up
In the top left, you can name your path specific to the sprite or object you are creating this path for. The path can either be absolute or relative.
-An absolute path is one that an instance use the path from that particular place.
-A relative path means the instance will start at the beginning of the path and follow it from there. Speed is on the right hand side of the box and has a starting value of 100.
This is the relative speed the instance will follow the path at.
To increase the speed, set the value greater than 100.
To decrease the speed of the instance, set the value less than 100.
Speed is interpolated between points on your path, so the speed changes gradually. To add a point, press the ADD button. A copy of the selected box will apear just below the box with all the path points. Now you can change the speed and the X and Y co-ordinates you want the instance to follow. Press INSERT to add a point before the selected and DELETE to delete the selected point. On the right side, the actual path resides. If one specific point is selected, the point will show up as red on the path. All other points will show up as blue and the starting point will be a green square. To add points on the image, click anywhere, if you hold the <shift> key and click, it will preform the same function.
By clicking the right mouse you can delete points. The points should allign with the grid.
To change the grid settings, click on the toolbar above.
You can control the size of the grid, and whether or not the grid is visible.
To precisely position a grid, hold the <alt> key before you left click. You can alther the shape of the path in 2 ways.
1. Change the connections to smooth or straight lines
2. Indicate whether or not the path is open or closed. In order to save the changes you make, click the 1st icon in the order from left to right on the toolbar.
If you want to get rid of you changes, then click the 2nd icon and no changes will be saved.
The following toolbar options alter the path that you created. The third option clears the path, reverses the order in which the path is traversed, shifts the path, mirrors it horizontally, flip it vertically, rotate it, and scale it.
Next are the buttons to shift the view and to center the view.
The "snap" button and the option of showing the grid.
Lastly, there is a button that allows you to see the level you are creating the path for. This is helpful when you want an object to follow your level. To assign a path to an instance of an object, you can place the path action in some event, like in the creation event. You must specify the path from the drop down menu. You must indicate the path that must be followed and the speed in pixels per step. When the speed is positive the instance starts at the beginning of the path. If it is negative it starts at the end. When you define the path you specify the actual speed relative to the indicated speed. There is also an action to change the speed with which the path is executed. For example, use this to let an instance slow down or speed up along its path. Also things like gravity and friction do not influence the motion along a path.
Assigning Paths to Objects Next you specify the end behavior, what should happen when the end of the path is reached. You can choose to stop the motion and end the path. You can also restart the path from the beginning, the instance jumps back to the position where the path begins abd executes the path again. A third option is to restart from the current position, that is, the instance follows the path again but now with this new starting position. Finally you can choose to reverse the motion, making the instance go back and forth along the path. At the end of the path an event happens.
Finally you can indicate whether the path must be absolute or relative. An absolute path is executed at the place where it is defined. The instance is placed at the start position and moved from there (end position when speed is negative). This is useful when you have a race track on which you have defined the path. When you choose relative the instances starts executing the path from its current position. This is useful when an instance should make a local motion. For example, space ships in a space invader game can make a particular turn from their current position.
You might wonder what happens when the instance collides with another instance while it follows a path. Basically the same happens as when the instance moves with a speed. When there is a solid instance, the instance is placed back at its previous location. When both instances are not solid they are placed at their new positions Next the collision event(s) are executed and it is checked whether the collision has been resolved. If not and the other instance is solid the instance will stop, as it should (if there is a collision event defined). When the blocking instance disappears the instance will continue to follow its path. To handle collisions yourself the variable path positionprevious can be useful. It holds the previous position for the path and you can set the path position to this variable to avoid advancing along the path.
As described above, you can indicate what must happen when the instance reaches the end of the path. Also an End of Path event occurs. You can find it under the Other events. Here you can place actions such as destroying the instance, or let it start a different path. The Path event Here are the concepts that we are going to teach you