Game Maker - Touch Event

Question

I´m making my first game in Game Maker.

In the game i need to the user to draw a figure, for example a rectangle, and the game has to recognize the figure. How can i do this?

Thanks!

Answer 1

Well, that is a pretty complex task. To simplify it, you could ask him to place a succession of points, using the mouse coordinates in the click event, and automatically connect them with lines. If you store every point in the same ds_list structure, you will be able to check conditions of angle, distance, etc. This way, you can determine the shape. May I ask why you want to do this ?

Answer 2

The way I would solve this problem is pretty simple. I would create a few variables for each point when someone clicked on one of the points it would equal true. and wait for the player to click on the next point. If the player clicked on the next point i would call in a sprite as a line using image_angle to line both points up and wait for the player to click the next point.

Next I would have a step event waiting to see if all points were clicked and when they were then to either draw a triangle at those coordinates or place an sprite at the correct coordinates to fill in the triangle.

Another way you could do it would be to decide what those points would be and check against mouse_x, and mouse_y to see if that was a point and if it was then do as above. There are many ways to solve this problem. Just keep trying you will find one that works for your skill level and what you want to do.

Answer 3

You need to use draw_rectangle(x1, y1, x2, y2, outline) function. As for recognition of the figure, use point_in_rectangle(px, py, x1, y1, x2, y2).

Answer 4

I'm just wondering around with ideas cause i can't code right now. But listen to this, i think this could work.

We suppose that the user must keep his finger on touchscreen or an event is triggered and all data from the touch event is cleaned.

I assume that in future you could need to recognize other simple geometrical figures too.

1 : Set a fixed amount of pixels of movement defined dependent on the viewport dimension (i'll call this constant MOV from now on), for every MOV you store in a buffer (pointsBuf) the coordinates of the point where the finger is.

2 : Everytime a point is stored you calculate the average of either X and Y coordinates for every point. (Hold the previous average and a counter to reduce time complexity). Comparing them we now can know the direction and versus of the line. Store them in a 2D buffer (dirVerBuf).

3 : If a point is "drastically" different from the most plain average between the X and Y coordinates we can assume that the finger changed direction. This is where the test part of MOV comes critical, we must assure to calculate an angle now. Since only a Parkinsoned user would make really distorted lines we can assume at 95% that we're safe to take the 2nd point that didn't changed the average of the coordinate as vertex and let's say the last and the 2nd point before vertex to calculate the angle. You have now one angle. Test the best error margin of the user to find if the angle is about to be a 90, 60, 45, ecc.. degrees angle. Store in a new buffer (angBuf)

4 : Delete the values from pointsBuf and repeat step 2 and 3 until the user's finger leaves the screen.

5 : if four of the angles are of 90 degrees, the 4 versus and two of the directions are different, the last point is somewhat near (depending from MOV) the first angle stored and the two X lines and the Y lines are somewhat equal, but of different length between them, then you can connect the 4 angles using the four best values next to the 4 coordinates to make perfect rectangular shape.

It's late and i could have forgotten something, but with this method i think you could even figure out a triangle, a circle, ecc.. With just some edit and confronting.

EDIT: If you are really lazy you could instead use a much more space complexity heavy strategy. Just create a grid of rectangles or even triangles of a fixed dimension and check which one the finger has touched, connect their centers after you'have figured out the shape, obviously ignoring the "touched for mistake" ones. This would be extremely easy to draw even circles using the native functions. Gg.