Need help and opinion on tank game problem

[Shawn]

Okay I uploaded a quick video to youtube to show what my issue is because its a lot easier if you can just see it. Anyway, I can't figure out how to animate the tank actually going up the slope. It doesn't angle upwards in its current state. I should also mention I'm using the PMO with it currently. Basically when the tank goes up the slope it stays the same angle as if its moving on flat ground.

So I need to know how I might change that, and if it looks bad the way it is. Should I just say to heck with it and leave it like it is?

http://www.youtube.com/watch?v=tbzwBKo2pCE

I tried using detectors and changing the animation to an angle when on a slope, but that was extremely buggy and just didn't work properly.

[variant]

I would just leave it the way it is and use more flat surfaces.

-Variant

[Shawn]

I would just leave it the way it is and use more flat surfaces.

-Variant

Yeah that's another thing I considered. Just removing slopes altogether and making ledges/cliffs instead.

I think I'm just going to leave the tank movement the way it is, because I can't come up with a bug-free way to fix that.

[UltimateWalrus]

Don't give up! :]

I almost never use detectors unless they're absolutely necessary. I find that 90% of the time, a fastloop works much better.

Here's what I would do:

1.) Create two invisible objects. I'll call them wheel1 and wheel2.
2.) At the start of each cycle, put wheel1 on top of the first wheel, and wheel2 on top of the second wheel.
3.) Start a fastloop. The number of times you run this fastloop will relate to the maximum angle of your tank. For now let's just say you run the loop 100 times.
4.) Each fastloop, move both wheels down 1 pixel.
5.) During the fastloop, if a wheel is overlapping a backdrop, move them back up 1 pixel.
6.)Now you should have two invisible wheel objects resting on the ground.
7.)Set the angle of your tank to atan2(Y("wheel2")-Y("wheel1"), X("wheel2")-X("wheel1")) or something like that.

[nivram]

Just curious...the "wheels" aren't detectors?

Marv

[UltimateWalrus]

Well I suppose in a sense they are. But I think that in the context of Clickteam products, "detector" implies an object that is always at a fixed position relative to another object, for the purpose of detecting collisions on a certain side of an object. The invisible wheels would be a little more advanced than a traditional "detector," because they are using fastloops to adjust their position dynamically depending on where the obstacles are.

[Shawn]

Don't give up! :]

I almost never use detectors unless they're absolutely necessary. I find that 90% of the time, a fastloop works much better.

Here's what I would do:

1.) Create two invisible objects. I'll call them wheel1 and wheel2.
2.) At the start of each cycle, put wheel1 on top of the first wheel, and wheel2 on top of the second wheel.
3.) Start a fastloop. The number of times you run this fastloop will relate to the maximum angle of your tank. For now let's just say you run the loop 100 times.
4.) Each fastloop, move both wheels down 1 pixel.
5.) During the fastloop, if a wheel is overlapping a backdrop, move them back up 1 pixel.
6.)Now you should have two invisible wheel objects resting on the ground.
7.)Set the angle of your tank to atan2(Y("wheel2")-Y("wheel1"), X("wheel2")-X("wheel1")) or something like that.

I have a system now that almost works, but I can't figure out the math :P How exactly do I find the angle between the 1st and 2nd wheel and have the tank change to that angle? Yeah... math isn't my strong suit.

[Game_Master]

Take a look at the Zeb example on the second MMF2 CD ROM. It has him walk up and down ramps/slopes like you want to do here.

[UltimateWalrus]

If you're using the latest version of MMF2, it should have the atan2 function which'll give you exactly what you need.

The exact expression you should use looks something like this:


Tank sprite --- Set Angle to:
-1*ATan2(Y("wheel2")-Y( "wheel1" ), X("wheel2")-X( "wheel1" ))


ATan2 is a function that takes an X/Y vector and uses the Tangent function to give you the angle (in degrees) of that vector. You always put the Y component first (because the tangent will be using y/x).

The reason it's negative is that MMF's sprite rotation ignores the fact that +Y points down.

Does that make sense?

[00J]

The reason it's negative is that MMF's sprite rotation ignores the fact that +Y points down.

Does that make sense?

Is that so? Interesting. Why would this be the case? not logical? Or is it just not logical to us humans?