Card Movement: 1 Step Forward and 2 Steps Back

Well the good news is amazing, my initial dive into coding in Unity has proven fruitful! I have been able to click a card on my screen and drag it anywhere around the gameboard! To add to that functionality I was able to make the card remain in its new location when it was dropped, which was a lot simpler than I thought it would originally be.

This simple movement of the cards is handled in Unity by two built in functions in a C# script:

OnMouseDrag () and OnMouseUpAsButton()

These two functions sense when the mouse has been clicked down on the card and when the card has been released respectively. Focusing on OnMouseDrag, I run two lines of code to make sure that the card object stays with the mouse so long as the player keeps the mouse pressed while dragging it across the screen. The first line is used to grab the coordinates of the mouse as a reference, and the second line takes the mouse coordinates and changes the cards coordinates to match the cards every single frame. These two lines are shown below:

Vector 3 WhereIsMouse = new Vector3 (Input.mousePosition.x, Input.mousePosition.y, distanceFromCamera);

Vector3 objectPosition = Camera.main.ScreenToWorldPoint(WhereIsMouse);

The coordinate values in unity are handled on a 3D plane, with x, y, and z axes. The unity system handles these coordinates using the Vector3 data type, which holds each of these axes as a value in a 3 element list, (x, y, z). By using two of these Vector3 objects I am able to both track where the mouse is in comparison to the camera, and change the coordinates of the object being dragged.

This is my one step forward, and as I promised in the title, I have had some problems that have set me back.

As long as something works, something else has to break. I was ecstatic when I was able to get the card movement to work, so with adrenaline coursing through my veins, I set off to achieve bigger and better things. I Thought “The card moves, now its time to make it snap to a location on the board!” This went well at first, as I was able to use another built in function in unity to detect the collision of a card above a board location (there will be more on that function in my next post). However, when I attempted to make this code work for all 9 board locations, instead of just one, I ran into a multitude of complications.

Everything from the dragging suddenly not working, to the cards in my game bugging out and flying off into space began to happen to my program. Most of these issues I couldn’t explain or even reproduce for others to help me with. So here I am, staring at a bunch of broken code with one thought in mind, “I have to restart”. I have taken this initial dive, and learned a lot in the process. Now its time to put that knowledge to the test, go a little behind schedule, and reproduce a better set of scripts that better suit my needs. Next goal on my list, get all five cards to snap to different locations on the board without my code breaking!

Next time I will be exploring more in depth what I mean by cards “snapping” to the board, as well as showing snippets of my code to explain where I went wrong in my previous iteration. Until next time.



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