Projectiles bounding boxes not functioning

ID:891374
 
Jul 26 2012, 4:08 pm
(See the best response by Kaiochao.)
Code:
obj/_projectile
    density = 1
    var
        mob/owner
        base_damage
        max_damage
        damage
        crit_probability
//////////////////////////////////////////////////////////////////////
        default_while = 1
        angle
        vel_x //vector angle calculations
        vel_y
        acc_x = 0 //acceleration
        acc_y = 0
        x_init = 0 //initial position
        y_init = 0
        x_offset = 0
        y_offset = 0
        vel_multiplier = 8
        direction
        move_counter
        move_limit

    //The following is treated as if you're facing north initially with passed values and such
    New(mob/o, _angle, _acc_x, _acc_y) //input angle upon owner's direction upon creation
        owner = o
        direction = owner.dir
        angle = _angle //should be 0 to 180
        acc_x = _acc_x
        acc_y = _acc_y
        var/own_bh = round(owner.bound_height/2)
        var/own_bw = round(owner.bound_width/2)
        var/bh = round(bound_height/2)
        var/bw = round(bound_width/2)

        y_init = owner.step_y + own_bh - bh
        x_init = owner.step_x + own_bw - bw

        switch(direction) //we need to alter acceleration here, too
            if(NORTH)
                y_init += own_bh //

            if(SOUTH)
                angle += 180

                y_init += -own_bh //later issues could come from subtracting a negative
                y_offset = -y_offset

                acc_x = -acc_x
                acc_y = -acc_y

            if(EAST || SOUTHEAST || NORTHEAST)
                angle -= 90

                x_init += own_bw

                x_offset += y_offset //swap values
                y_offset = x_offset - y_offset
                x_offset -= y_offset

                acc_x += acc_y //swap values
                acc_y = acc_x - acc_y
                acc_x -= acc_y

            if(WEST || SOUTHWEST || NORTHWEST)
                angle += 90

                x_init += -own_bw //later issues could come from subtracting a negative

                x_offset += y_offset //swap values
                y_offset = x_offset - y_offset
                x_offset -= y_offset

                x_offset = -x_offset //reverse x_offset

                acc_x += acc_y //swap  values
                acc_y = acc_x - acc_y
                acc_x -= acc_y

                acc_x = -acc_x //reverse acc_x

        vel_x = cos(angle) * vel_multiplier  //velocity in the X direction
        vel_y = sin(angle) * vel_multiplier //velocity in the Y direction
        
        Create()

    //this would be the start of a new proc called Create() once testing is complete
    proc/Create()
        loc = owner.loc

        step_x = x_init + x_offset
        step_y = y_init + y_offset

        if(default_while)
            while(src)
                move_counter ++
                if(move_counter > move_limit)
                    del src
                sleep(world.tick_lag)

                // shift the position by the velocity vector
                step_x += vel_x + acc_x
                step_y += vel_y + acc_y

                // shift the velocity vector by the acceleration vector
        //      vel_x += acc_x
            //  vel_y += acc_y
            
    fireball
        density = 1
        icon = 'fireball_test.dmi'
        bound_width = 16
        bound_height = 16
        y_offset = 10
        vel_multiplier = 3
        move_limit = 999


Problem description:

No matter what I do, when I create one of these projectiles, their bounding boxes are not functioning. They go through everything and exit the map. I'm not sure what the problem is here. I've tried changing them to mobs. I've tried using the Cross() proc but nothing is picked up.

(Note that I am NOT using Forum_Account's Pixel Movement)

#1 Jul 26 2012, 4:47 pm
Collision is only detected automatically when you use Move() to move objects. That includes procedures like step(), which use Move().

Otherwise, you'll have to do obounds() to search for dense things, but that gets complicated and doesn't take advantage of the built-in pixel movement support (it's a lot of pre-native-pixel-movement calculation that not many people are used to).

Also, vel_multiplier is also called "speed".
#2 Jul 26 2012, 4:55 pm
In response to Kaiochao (#1)
I understand what you're saying, but why isn't it as simple as this:

                // shift the position by the velocity vector
                step_x += vel_x + acc_x
                step_y += vel_y + acc_y

                Move(src, dir, step_x, step_y)


Because I thought it would be, but of course it doesn't work =( .
#3 Jul 26 2012, 5:04 pm
In response to Cloud Magic (#2)
Best response
Objects don't bump into things they're already inside of. That's probably something important that you need to know.

So instead, you could try this:
Move(loc, dir, step_x + vel_x + acc_x, step_y + vel_y + acc_y)


Also, I really don't want to know what you're doing at all; I don't feel like reading any of your code. Acceleration is added to velocity each tick, and velocity is added to position each tick. That's pretty much how basic "motion physics" goes in games.
//  e.g.
tick() //  called each tick for every physics mover
    vel_x += accel_x
    vel_y += accel_y
    pos_x += vel_x
    pos_y += vel_y
#4 Jul 26 2012, 8:47 pm
In response to Cloud Magic (#2)
Cloud Magic wrote:
I understand what you're saying, but why isn't it as simple as this:

>               // shift the position by the velocity vector
>               step_x += vel_x + acc_x
>               step_y += vel_y + acc_y
>
>               Move(src, dir, step_x, step_y)


Because I thought it would be, but of course it doesn't work =( .

This would work, if you used variables for the first 2 lines instead of modifying step_x and step_y, because those update automatically.
#5 Jul 26 2012, 8:51 pm
Well, I tried changing to using the Move() method and I have to say, the projectiles are now coming out very buggy and insanely fast. They stop at map boundaries, but as far as mobs go, they seem to move right through them.

Here is the updated code:

obj/_projectile
    density = 1
    var
        mob/owner
        base_damage
        max_damage
        damage
        crit_probability
//////////////////////////////////////////////////////////////////////
        default_while = 1
        angle
        vel_x //vector angle calculations
        vel_y
        pos_x //locations
        pos_y
        acc_x = 0 //acceleration
        acc_y = 0
        x_init = 0 //initial position
        y_init = 0
        x_offset = 0 //starter offset
        y_offset = 0
        vel_multiplier = 2 //speed
        direction
        move_counter
        move_limit

    //The following is treated as if you're facing north initially with passed values and such
    New(mob/o, _angle, _acc_x, _acc_y) //input angle upon owner's direction upon creation
        owner = o
        direction = owner.dir
        angle = _angle //should be 0 to 180
        acc_x = _acc_x
        acc_y = _acc_y
        var/own_bh = round(owner.bound_height/2)
        var/own_bw = round(owner.bound_width/2)
        var/bh = round(bound_height/2)
        var/bw = round(bound_width/2)

        y_init = owner.step_y + own_bh - bh
        x_init = owner.step_x + own_bw - bw

        switch(direction) //we need to alter acceleration here, too
            if(NORTH)
                y_init += own_bh //

            if(SOUTH)
                angle += 180

                y_init += -own_bh
                y_offset = -y_offset

                acc_x = -acc_x
                acc_y = -acc_y

            if(EAST || SOUTHEAST || NORTHEAST)
                angle -= 90

                x_init += own_bw

                x_offset += y_offset //swap values
                y_offset = x_offset - y_offset
                x_offset -= y_offset

                acc_x += acc_y //swap values
                acc_y = acc_x - acc_y
                acc_x -= acc_y

            if(WEST || SOUTHWEST || NORTHWEST)
                angle += 90

                x_init += -own_bw

                x_offset += y_offset //swap values
                y_offset = x_offset - y_offset
                x_offset -= y_offset

                x_offset = -x_offset //reverse x_offset

                acc_x += acc_y //swap  values
                acc_y = acc_x - acc_y
                acc_x -= acc_y

                acc_x = -acc_x //reverse acc_x

        vel_x = cos(angle) * vel_multiplier  //velocity in the X direction
        vel_y = sin(angle) * vel_multiplier //velocity in the Y direction

        Create()

    //this would be the start of a new proc called Create() once testing is complete
    proc/Create()
        loc = owner.loc

        //step_x = x_init + x_offset
        //step_y = y_init + y_offset

        Move(loc, dir, x_init + x_offset, y_init + y_offset)




        if(default_while)
            while(src)
                sleep(world.tick_lag)
                move_counter ++
                if(move_counter > move_limit)
                    del src
        //

                // shift the position by the velocity vector
                //step_x += vel_x + acc_x
                //step_y += vel_y + acc_y
                pos_x += vel_x + acc_x
                pos_y += vel_y + acc_y

                Move(src.loc, dir, pos_x, pos_y)


                // shift the velocity vector by the acceleration vector
        //      vel_x += acc_x
            //  vel_y += acc_y

    fireball
        density = 1
        icon = 'fireball_test.dmi'
        bound_width = 16
        bound_height = 16
        y_offset = 10
        vel_multiplier = 1
        move_limit = 999


Note that when using step_x and step_y, as I did above, this system is working perfectly smooth.
#6 Jul 26 2012, 8:54 pm
You probably want to set pos_x and pos_y to their step_x and step_y after moving them.
#7 Jul 26 2012, 9:05 pm
In response to Albro1 (#6)
Wow...I'm not sure why, but your suggestion worked!!!
#8 Jul 26 2012, 9:08 pm
In response to Cloud Magic (#5)
It's because step_x and step_y are your pixel position on the current tile. As such, they only go from 0-32. So, if pos_x is 46 and you add 4, you're going to move 50 pixels.