----------------------------------- lordroba Fri Aug 12, 2005 9:26 am Hasch question, cheking to see if key pressed ----------------------------------- I'm making a racing game and I want the car speed up while the UP key is being pressed(i know how to do this), and I want the speed to slowly go down while no key is pressed. How do I check if no key is being pressed and put this into an 'IF' condition so that it lowers the value of the speed variable when this is true? ----------------------------------- MihaiG Fri Aug 12, 2005 10:59 am ----------------------------------- heres a small example if not hasch then speed := speed - 1 %speed -= 1 end if ----------------------------------- lordroba Fri Aug 12, 2005 11:07 am ----------------------------------- thank you very much ----------------------------------- Cervantes Fri Aug 12, 2005 11:32 am ----------------------------------- Use Input.KeyDown, not hasch and getch. It will allow you to get multiple keystrokes at once. You probably don't want to slow your car down when no key is pressed. Think about it: the user could press "h" and he would go at a constant speed and not use any fuel or anything. Instead, you want the car to slow down when the up arrow is not pressed. if keys (KEY_UP_ARROW) then car.speed += car.acceleration else car.speed *= car.deceleration end if car.deceleration should be slightly less than 1. 0.99 is a good value to test. Of course, you could use some physics to determine accelerations with regard to mass, applied force, and frictional forces. View.Set ("offscreenonly") var car : record x, y : real mass : real internal_friction, net_force : real current_vert_angle : real speed, applied_engine_force : real current_surface_material, tire_material : string end record := init (100, 100, 800, 200, 0, 0, 0, 10000, "dry asphault", "rubber") type Friction_Coefficient : record surface1, surface2 : string value : real end record fcn friction_coeffecient_init (surface1, surface2 : string, value : real) : Friction_Coefficient var temp_coeff : Friction_Coefficient temp_coeff.surface1 := surface1 temp_coeff.surface2 := surface2 temp_coeff.value := value result temp_coeff end friction_coeffecient_init var coefficients : array 1 .. 2 of Friction_Coefficient coefficients (1) := friction_coeffecient_init ("rubber", "dry asphault", 0.6) coefficients (2) := friction_coeffecient_init ("rubber", "wet asphault", 1.2) fcn friction_force (surface1, surface2 : string, N : real) : real for i : lower (coefficients) .. upper (coefficients) if Str.Lower (coefficients (i).surface1) = Str.Lower (surface1) and Str.Lower (coefficients (i).surface2) = Str.Lower (surface2) then %Force of friction = mew (coefficient of friction) * Normal force result coefficients (i).value * N end if end for end friction_force var keys : array char of boolean loop car.net_force := -car.internal_friction - friction_force (car.tire_material, car.current_surface_material, cosd (car.current_vert_angle) * car.mass * 9.8) %- car.speed % the last bit, - car.speed is an approximation for wind resistance. I'm not sure how wind resistance works. Anyone know the formula? Input.KeyDown (keys) if keys (KEY_UP_ARROW) then car.net_force += car.applied_engine_force end if car.speed += car.net_force / car.mass car.speed := max (0, car.speed) car.x += car.speed car.x mod= maxx cls Draw.FillOval (round (car.x), round (car.y), 10, 10, black) locate (1, 1) put car.speed View.Update delay (10) end loop I think this is all correct, except for the fact that the coefficient of friction changes depending upon your speed. This also does not take into account air resistance, which is greater than the friction between the tires and the road. ----------------------------------- lordroba Sat Aug 13, 2005 9:00 am ----------------------------------- Alright now i'm really pissed, I spent all day yesterday trying to figure this out but I'm having no success. :x As you can see in the attached program, the car moves fine, and it turns and everything, but I can't figure out how to make it keep going for a while when you let go of the acceleration(UP) button! It just stops right where you let go of the key. can someone plz help me. I not only want the car to move a fair bit and eventually stop after you let go of the gas, but I also want it so that the user still has ability to steer the car thru the corner when its moving. Any help greatly appreciated! ----------------------------------- Cervantes Sat Aug 13, 2005 12:11 pm ----------------------------------- There are two tutorials you should look at: First, check out zylum's player.x += cosd (player.dir) * player.forward_speed player.y += sind (player.dir) * player.forward_speed You want that to happen all the time. He won't move if his speed is 0, remember. Here's the modified code. var winID := Window.Open ("graphics:1200;800,nobuttonbar,offscreenonly") colourback (2) var player : record x, y : real angle : real speed : real rotation_speed : real forward_accel : real backward_accel : real max_forward_speed : real max_backward_speed : real end record player.x := 100 player.y := 100 player.angle := 90 player.speed := 0 player.rotation_speed := 5 player.forward_accel := 1 player.backward_accel := 0.5 player.max_forward_speed := 10 player.max_backward_speed := -5 var picCar := Pic.FileNew ("Trueno.bmp") var picCarRotated := Pic.Rotate (picCar, round (player.angle), Pic.Width (picCar) div 2, Pic.Height (picCar) div 2) var picRoad := Pic.FileNew ("Road1.jpg") procedure playerControls var keys : array char of boolean Input.KeyDown (keys) if keys (KEY_RIGHT_ARROW) & player.speed ~= 0 then player.angle := (player.angle - player.rotation_speed) mod 360 end if if keys (KEY_LEFT_ARROW) & player.speed ~= 0 then player.angle := (player.angle + player.rotation_speed) mod 360 end if if not keys (KEY_UP_ARROW) & not keys (KEY_DOWN_ARROW) then if player.speed = -0.5 then player.speed := 0 end if player.speed *= 0.97 else if keys (KEY_UP_ARROW) then player.speed := min (player.max_forward_speed, player.speed + player.forward_accel) end if if keys (KEY_DOWN_ARROW) then player.speed := max (player.max_backward_speed, player.speed - player.backward_accel) end if end if end playerControls procedure updatePlayer playerControls player.x += cosd (player.angle) * player.speed player.y += sind (player.angle) * player.speed picCarRotated := Pic.Rotate (picCar, round (player.angle), Pic.Width (picCar) div 2, Pic.Height (picCar) div 2) Pic.Draw (picCarRotated, 600, 400, picMerge) Pic.Free (picCarRotated) put player.x, " ", player.y, " ", player.speed end updatePlayer loop cls Pic.Draw (picRoad, -round (player.x), -round (player.y), picCopy) updatePlayer View.Update end loop Window.Close (winID) I also rotated the picture by 90°, so you don't have to bother with the Pic.Rotate in the initialization stages. ----------------------------------- [Gandalf] Sat Aug 13, 2005 3:52 pm ----------------------------------- I was wondering how would you check if the user hit any key at all, not everything (including having no key pressed at all) except some certain keys. Can't think of anything right now :?... Thanks. ----------------------------------- Cervantes Sat Aug 13, 2005 4:17 pm ----------------------------------- Could you restate that? ----------------------------------- [Gandalf] Sat Aug 13, 2005 9:07 pm ----------------------------------- Yeah, I knew it was a bit unclear... When you have an Input.Keydown statment, like if keys ('a') then ... and then you add an else, that else will include when no keys are pressed at all. I only want to do something when an actual key is pressed (when a key is pressed that is not 'b' for example). Basically, I want to do an 'else' like statement but without a null key - I can't think of how to detect that. Probably a pretty simple solution, but I've been wondering for a while and decided to ask. ----------------------------------- Cervantes Sun Aug 14, 2005 7:11 am ----------------------------------- if hasch and not keys ('b') then "]When you have an Input.Keydown statment, like if keys ('a') then ... and then you add an else, that else will include when no keys are pressed at all. The else would be entered only if 'a' is not pressed. Other conditions, such as if 'b' is pressed, are irrelevent. ----------------------------------- [Gandalf] Sun Aug 14, 2005 5:56 pm ----------------------------------- Ok, thanks. I wasn't thinking about hasch/getch, trying to avoid it. Is there a way of doing it without them? Still, it's a pretty good use of hasch (as opposed to using it as a replacement of Input.Keydown). I know about the else statment, I was just trying to explain the problem that I can't detect if keys(nothingatall). ----------------------------------- Cervantes Sun Aug 14, 2005 7:04 pm ----------------------------------- I agree: I try to avoid using hasch & getch with Input.KeyDown, because of problems with one catching keystrokes that I want the other to catch. Here's another way to do it. There's some need tricks in here, particularly the range of the for loop. var keys : array char of boolean fcn key_pressed_other_than (key : char, keyboard : array char of boolean) : boolean if keyboard (key) then result false end if for i : char if keyboard (i) then result true end if end for result false end key_pressed_other_than loop Input.KeyDown (keys) locate (1, 1) if key_pressed_other_than ('b', keys) then put "A key has been pressed other than 'b'" else put "'b' has been pressed, or no key has been pressed" end if exit when keys (KEY_ESC) end loop ----------------------------------- [Gandalf] Sun Aug 14, 2005 11:18 pm ----------------------------------- Nice. I'll try it out later on, thanks again :). Interesting way of doing it, I was wondering about different for loops, now I have something to think about.