Collision not working? What am i doing wrong

[Abbas_M]

What is it you are trying to achieve?
I was really confused about collisions but now i understand them a little, im trying to make my moving spaceship hit a non moving zombie and the result
becoming an exit.


What is the problem you are having?
I have alll the code written but its not working. My space ship only move vertically (up and down) on the left side of the screen. only the y1 value changes of the space ship and nothing else. the zombie stays still. but my spaceship just passes the zombie and no collison



Describe what you have tried to solve this problem
Repeatdly read the tutorial used other ones got examples and tried changing around the values still nothing


Post any relevant code (You may choose to attach the file instead of posting the code if it is too long)

Turing:

x1 := 15     y1 := 220     x2 := 100 + 15     y2 := 100 + 220     a1 := 15     b1 := 400     a2 := 65 + 15     b2 := 65 + 400     fork ingamemusic     loop         Input.KeyDown (chars)         %Main Movement Seqeunce         if chars (KEY_UP_ARROW) then             y1 := y1 + 5         end if         if chars (KEY_DOWN_ARROW) then             y1 := y1 - 5         end if                 %ship is the variable for the image of the ship         %picture4 is the background         %picture2 is my zombie         Pic.Draw (picture4, 3, -50, picMerge)         Pic.Draw (ship, x1, y1, picMerge)         delay (2)         Pic.Draw (picture2, 15, 400, picMerge)         View.UpdateArea (0, 0, maxx, maxy)         Pic.Draw (ship, x1, y1, picMerge)               if x2 > a1 and x1 < a2 and y2 > b1 and y1 < b2 then             put "They have collided!"             exit         end if         cls         %Boundrie to Up         if y1 > 419 then             y1 := y1 - 10         end if         %Boundrie to Down         if y1 < -15 then             y1 := y1 + 10         end if     end loop

Please specify what version of Turing you are using
4.1.1

for some reason its not working. my variables are decleared and everything. no errors. when it runs it doesnt detect collide just goes through. I hope someone can help me out.

[TheGuardian001]

you never actually change y2 at any point in this program. The image might be moving, but as far as the collision detection is concerned it's sitting right back where it started.

Every time you change y1, you should be resetting y2 to the new location, IE

code:

y1 += 5 y2 = y1 + Pic.Width(img)

which should fix your problem

[Abbas_M]

it dint work still have same problem it just passes the zombie without any detection. would it be better if i attach my program so people can take a look at the entire code?

[TheGuardian001]

Probably, however upon further inspection:

code:

if x2 > a1 and x1 < a2 and y2 > b1 and y1 < b2 then             put "They have collided!"             exit end if

is stating that the ship must be fully inside of the zombie. This is probably not what you want. You need to be less specific and check if any part overlaps, so for example

code:

if player_upper_y > enemy_lower_y and player_upper_y < enemy_upper_y then %top edge y axis collides     if player_right_x > enemy_left_x and player_right_x < enemy_right_x then %right edge y axis collides         collision! (top right corner of ship only)     end if end if

[Abbas_M]

still not working out. i tried repositiong the zombie so he would be a bit away from the ship and edges would collide but nothing. it didn't work out. Ima attach my game and you can see and tell me if something is wrong. it very cheasy but its my first ever game so...

[TerranceN]

From reading your updated code, I can see all you changed was moving some stuff around.

Like what TheGuardian001 said, make sure you are updating the top right co-ordinates. If you don't change them, you are not checking collision for the right co-ordinates, and the collision between the ship and alien will never be detected.

Second, read richcash's Collision Detection Tutorial, it tells you how to check for collision.

Finally, try adding this before your View.UpdateArea, it will help you visualize the problem.

Turing:

drawfilloval(x1, y1, 5, 5, blue) drawfilloval(x2, y2, 5, 5, blue) drawline(x1, y1, x1, y2, blue) drawline(x1, y2, x2, y2, blue) drawline(x2, y2, x2, y1, blue) drawline(x2, y1, x1, y1, blue)         drawfilloval(a1, b1, 5, 5, green) drawfilloval(a2, b2, 5, 5, green) drawline(a1, b1, a1, b2, green) drawline(a1, b2, a2, b2, green) drawline(a2, b2, a2, b1, green) drawline(a2, b1, a1, b1, green)

Hope that helps.

[Abbas_M]

Omg thank you so much that diagram you made helped alot it explained a bunch to me and i got collision working. I do have 1 more question which would be better for my rectangular collision or circular. thanks for the help.

Edit: i tested both rectangular and circular collision detection method and circular was more accurate. in rectangular the alien and spaceship were not even touching and it said crash. circular there is physical contact before it says crash so i think il go with circular. if someone has a reason i should not please let me know. Thanks for all the help TheGuardian001 and TerranceN really appreciate it

[TerranceN]

Really just use whatever collision you feel more confident using, because your game will probably be going fast enough that small imprefections in collision detection will not be noticed. And if it is a big problem just decrease the size in your collision calculations.

Also, look at how much blank space there is for your ship. If you resize the image so there is less blank space, the rectangular collision will be more precise than it was before.
Try this image:

[Abbas_M]

yeah the circular collision is working pretty good right now but if it starts to act up later il switch to rectangular thanks for the help