Help with collision detection for Space Invaders Remake.

[Degensquared]

Thanks in advance for any help I you can give me

I fire the lazer, and it just goes right through enemy, and does not do damage to the enemy.
But, certain times, it kills enemys when you are sitting dirrectly below them, without the lazer damaging them.

Turing:

View.Set ("graphics:800;600,offscreenonly") %Variables var x, hitleftwall, hitrightwall, firedelay, firedelaytime, totalfired, topenemy : int := 0 var lazerx, lazery, fired : array 1 .. 10 of int var enemyhp, enemyx, enemyy : array 1 .. 20 of int var chars : array char of boolean %settings x := 400 topenemy := 10 colorback (black) cls %Sets up the arrays for count : 1 .. topenemy     enemyhp (count) := 3     enemyx (count) := 50 + (50 * count)     enemyy (count) := 500 end for for count : 1 .. 10     fired (count) := 0 end for loop     Input.KeyDown (chars)     %Handles shooting the lazer     if chars (KEY_UP_ARROW) then         if firedelay = 0 then             if totalfired <= 9 then                 totalfired += 1                 fired (totalfired) := 1                 firedelay := 1                 lazerx (totalfired) := x                 lazery (totalfired) := 35             end if         end if     end if     %Moves tank to the right     if chars (KEY_RIGHT_ARROW) then         if hitrightwall = 0 then             x := x + 5         end if     end if     %Moves tank to the left     if chars (KEY_LEFT_ARROW) then         if hitleftwall = 0 then             x := x - 5         end if     end if     %To be used for special move sometime in future (like a sheild or bomb)     if chars (KEY_DOWN_ARROW) then     end if     %Collision detection with the let and right walls.     if x <= 25 then         hitleftwall := 1     elsif x >= 775 then         hitrightwall := 1     else         hitrightwall := 0         hitleftwall := 0     end if     %Creates a delay so that bullets can only fire every 10 frames.     if firedelay = 1 then         if firedelaytime < 10 then             firedelaytime += 1         else             firedelaytime := 0             firedelay := 0         end if     end if     %Checks for collision with enemy and lazer     for count : 1 .. topenemy         for count1 : 1 .. upper (fired)             if fired (count1) = 1 then                 if lazery (count1) >= enemyy (count) - 10 and lazerx (count1) = enemyx (count) - 30 or lazery (count1) <= enemyy (count) - 7 and lazerx (count1) = enemyx (count) + 30 then                     fired (count) := 0                     totalfired := 0                     if enemyhp (count) >= 1 then                         enemyhp (count) -= 1                     end if                 end if             end if         end for     end for     %Draws enemys with correct color     for count : 1 .. topenemy         if enemyhp (count) = 3 then             drawoval (enemyx (count), enemyy (count), 7, 7, green)         elsif enemyhp (count) = 2 then             drawoval (enemyx (count), enemyy (count), 7, 7, yellow)         elsif enemyhp (count) = 1 then             drawoval (enemyx (count), enemyy (count), 7, 7, red)         end if     end for     %Draws lazers and checks if they are off the screen.     for count : 1 .. upper (fired)         if fired (count) = 1 then             if lazery (count) <= 775 then                 lazery (count) += 5                 drawline (lazerx (count), lazery (count), lazerx (count), lazery (count) + 5, white)             else                 fired (count) := 0                 totalfired := 0             end if         end if     end for     %Checks if enemy is hit by lazer and then deletes lazer and takes away the hp.     for count : 1 .. topenemy         for count1 : 1 .. upper (fired)             if fired (count1) = 1 then                 if lazery (count1) >= enemyy (count) - 10 and lazerx (count1) = enemyx (count) - 30 or lazery (count1) <= enemyy (count) - 7 and lazerx (count1) = enemyx (count) + 30 then                     fired (count) := 0                     totalfired := 0                     if enemyhp (count) >= 1 then                         enemyhp (count) -= 1                     end if                 end if             end if         end for     end for     %Draws player     drawoval (x, 30, 8, 8, white)     drawline (x, 30, x, 43, white)     View.Update     delay (10)     cls end loop

Thanks

Degen.

[isaiahk9]

In theory here is what you should do :
Make it so that when the user fires a bullet, that bullet will have coordinates - x will be the x coordinate of your tank when the bullet was fired and the y will increase so it will fly across the screen.
Put the bullet in a for loop so that it's y coordinate will be slowly increased, and thus it will be moving upward when you draw it with its y coordinate.
Make x and y coordinates for the enemies or targets.
Say that if bullet x and y coordinates equal the target x and y coordinates, then that target is damaged.
That works - I tried it - but there might be something more efficient out there. However, this is the best I can come up with.

[Zampano]

He knows the entirety of coordinates, and used that. Theory is no object. The problem, I think, is here:

code:

if lazery (count1) >= enemyy (count) - 10 and lazerx (count1) = enemyx (count) - 30 or lazery (count1) <= enemyy (count) - 7 and lazerx (count1) = enemyx (count) + 30 then

You used x comparing conditions, you used '=' as opposed to '>' and '<', requiring the bullet to be at a specific x. And though I can't say, the addition of 30 seems more than a little arbitrary given the size of the enemies. Of course, this approach is use for collision detection for rectangles; for these circular enemies, you will know that the bullet is in the enemy is it's distance from the centre of the enemy is less than the enemy's radius. Thus, use int Distance.PointLine (int, int, int, int) to find the distance between those two points, and you are set for collision detection.

[isaiahk9]

Oh. That works better than mine, Zampano. I just thought that mine was simpler to follow. Guess not.