Calculate X/Y speed for 8Dir behavior relative to facing direction

You can set the velocity in a specific direction with a bit of trig:

Vx=100*cos(a)

Vy=100*sin(a)

You can also combine two velocities by adding them.

Vx=100*cos(a)+100*cos(b)

Vy=100*sin(a)+100*sin(b)

Then to limit the max speed you can do this

Speed=distance(0,0,vx,vy)
If speed>maxSpeed then
— vx = vx/speed*maxSpeed
— vy = vy/speed*maxSpeed

You can set the velocity in a specific direction with a bit of trig:

As always, you are among the awesome people who come to the rescue. THANK YOU! I remember having only a semester of trig in high school (c/o 1999... I'm old-ish LOL). So, trig didn't immediately come to mind. But it makes sense now that it would apply.

I'll work on adapting your solution after work today and let you know if that resolves the problem. Thanks again! God bless!

For the most part, I think I follow... But I have some clarifying questions.

You can set the velocity in a specific direction with a bit of trig:

Vx=100*cos(a)

Vy=100*sin(a)

To reword this in my own head (and how I am currently plugging into my project) in order to make sure I understand:

Player.Velocity_X = Player.8Direction.MaxSpeed * cos( Player.Angle )
Player.Velicity_Y = Player.8Direction.MaxSpeed * sin( Player.Angle )

Speed=distance(0,0,vx,vy)
If speed>maxSpeed then
— vx = vx/speed*maxSpeed
— vy = vy/speed*maxSpeed

R0J0hound - I realize I have a tendency to over-explain everything. LOL

So, hopefully, this better summarizes what my last comment was trying to get at.

First the distance(0,0,vx,vy) is correct. Vx,vy is the velocity vector and that gets the magnitude of that vector. For velocity the magnitude is the speed. You can also calculate it with sqrt(vx^2 + vy^2).

Anyways for motion logic you’d set vx and vy to zero and just add any directions you want.

The final step is to limit the speed to a max speed.

Here’s another possible way to do it. I mean you can apple the speed of 100 as a last step.

every tick
-- vx=0
-- vy=0

if up pressed
-- set a to player.angle
-- add cos(a) to vx
-- add sin(a) to vy

if right pressed
-- set a to player.angle+90
-- add cos(a) to vx
-- add sin(a) to vy

... etc for other directions

if vx<>0 and vy<>0
-- set mag to sqrt(vx^2+vy^2)
-- set vx to 100*vx/mag
-- set vy to 100*vy/mag

R0J0hound - As always, you are a lifesaver. Can't tell you enough how grateful I am for your help. THANK YOU.

It's a funny thing (to me) - your explanations made sense on their own but when it came to applying them, I kept getting lost on details and I couldn't exactly articulate what those details were. But I finally got it! Some of it was just the logic order of the conditions/actions in light of all the trig calculations. Along with some extra review (thank you, Google), I was better able to understand what you were getting at.

ANYWAY! Enough sentimentalism...

Here's what I plugged in and it WORKS! (I'm 41 and feeling like a kid who just his Lego set put together. Good stuff.)

Now, I'm not sure this was exactly what you had in mind, so if there is a more refined way of doing this, I'm not seeing it. The next step I need to do is to see if I can figure out how to make moving in diagonals possible. I believe this is what you meant by adding velocities together. I updated the logic to apply the trig calculations directly the 8 Direction behavior's velocity values instead of the instance variables I had been using (I think that was lending itself to some of my initial hang-ups).

I think I need to try to think outside the box to figure this one out on my own. I will request some extra help if I can't figure it out for some reason.

Thank you again!

That's close to what I meant. I think the 8direction behavior just gets in the way.

The 8direction behavior already limits the speed to the maxSpeed so all you need to do should be:

1. set velocity of x and y to 0.

2. when a direction key is pressed add to the velocity a direction vector:

maxSpeed*cos(a), maxSpeed*sin(a)

That should handle diagonals and such, unless something I'm not aware of occurs in the behavior.

An alternate idea is to have a hidden object with 8dir that you move normally but without collisions. The rotate that object's velocity and set the velocity of a visible object. It would give smoother speeding up and slowing down, but it still wouldn't update the velocity when hitting solids.

dropbox.com/s/v41o4p8qxsd5tdh/rotated_8dir.capx

Or here is an older example of the 8dir behavior done with events sans collisions. You just set the angle of the sprite and motion will be relative to that.

There may be a simpler way. I guess I didn't really answer your question. But having a few example of various ways to do it could be useful?

OH MY GOODNESS!! That may just be the solution (the Dropbox example)!!

Yeah, the use of 8 Direction is because of my need to have a check against objects with the Solid behavior. The custom movement system I had before was similar to the trig solution you've provided (setting movement angle to +/-90, et al).

Since going back to using 8 Direction, the whole problem was trying to get the keyboard input to reflect the 3D camera perspective (and therefore the facing angle of the Player) while taking into account that 8 Direction does not normally regard the camera perspective. That's why your trig solution was so pivotal.

However, using the "ghost sprite" object is genius! I'm going to work on adapting that now. I think you just solved the problem.