Basic Slope Detection Tutorial « Borne Games Forum

Borne Games Forum » Game Development

Basic Slope Detection Tutorial

(23 posts) (9 voices)

Started 2 years ago by Thefox
Latest reply from VideoGuy

Tags:

12 Next »

Thefox
Member
Post Count: 249

Hey all sorry for the wait. This week has been really busy with all my projects and school. But here is the tutorial:

In this tutorial I will teach you how to build a basic slope engine. Please take note that this slope engine will NOT work on slopes with an angle greater than 90 degrees.

For this tutorial I will assume you know how to make a character move on flat ground in flash.

So before we begin you will need a bit of knowledge in trigonometry (I will refer to this as trig from now on). Trig is all about the realtionships between the angles and sides in a triangle. Thus using trig you are able to find the angle between sides of a triangle, or the length of the sides based on the angle. In order to do this, you use the trig functions: Sin, Cos and Tan.

So now for how they work:
(I will be referring to this pic in the example of how to use these functions)
Sorry But currently I cant get the image tag to work...This pic is called tut.jpg in the zip file you download below

See the (put in ascii for theta) in that picture? That symbol is called theta and refers to a certain angle in the trangle seen in the picture. theta can be placed in any angle in that triangle but for this example it I will be using the above angle.
The text SOH CAH TOA is how sin cos and tan work, and SOH CAH TOA is a little trick for remembering how they work. Here's what the letters mean:
S = Sin, C = Cos, T = Tan, O = Opposite, A = Adjacent, H = Hypotenuse
Opposite being the site opposite of the angle (side A), Adjacent being the side adjacent to the angle (side B), and the hypotenuse (side C)
Now that you know what the symbols mean this is how it works:
SOH : The Sin of the angle (theta) is equal to the Opposite side over the Hypotenuse. (Shown in the text below SOH CAH TOA)
CAH : The Cos of the angle (theta) is equal to the Adjacent side over the Hypotenuse. (Shown in the text below SOH CAH TOA)
TOA : The Tan of the angle (theta) is equal to the Opposite side over the Adjacent side. (Shown in the text below SOH CAH TOA)

This is the minimum knowledge about trig you need to know for this tut. Thanks for hanging in there with me! Now for making our character move on slopes!!!

So here's our strategy in this. Now that we know how to find an angle between any side in a triangle, if we have one point above the character and one point as the middle of the character, we can find the angle of the slope. Check out the pic for a visual explanation
Sorry But currently I cant get the image tag to work...This pic is called tut-pic2.jpg in the zip file you download below

The rest of the tutorial is written inside the FLA file!

GRAB THE FILES HERE!!

Hope you guys enjoy! Any comments, suggestions and corrections are much appreciated!

-Fox

Posted 2 years ago #
Orange
Member
Post Count: 2105

i don't understand why one needs to know about sin and cos, only tan is used if you do it the way i talked about in my tut on the other topic. i can't see the rest of your tut though because i don't have flash.

Twitter!
Blog!

Posted 2 years ago #
Thefox
Member
Post Count: 249

sin and cos help you move on angles correctly

Posted 2 years ago #
Orange
Member
Post Count: 2105

what do you mean? i thought that only tan was needed to do that (in this type of thing).

Twitter!
Blog!

Posted 2 years ago #

Secret
Nyubis
Nyubis of Strata
Post Count: 9089

For the rotation, tan() is needed, but for the modified _x and _y movement, sin() and cos() is needed.

Not in cruelty
Not in wrath
the Reaper came today.

An angel visited
this gray path
And took the cube away.

Posted 2 years ago #
Orange
Member
Post Count: 2105

how do you use sin and cos to move things? and why would you need to?

Twitter!
Blog!

Posted 2 years ago #
Thefox
Member
Post Count: 249

Basically, Say I have a variable called MoveLR which contains the speed of the character. Now when i'm working with flat ground and not slopes I can just say _x += MoveLR. But since i'm moving on an angle now I cant do that. Why you ask? Well if i'm moving on say a 45 degree hill, when I move don't I move in BOTH the X and Y direction? Well if I want to find how much I move in the X direction and how much in the Y direction I have to use sin and cos. Remember my MoveLR (speed) is like the hypotenuse of a triangle. Sin and cos help me find the base and height of it (X and Y)

Posted 2 years ago #
Orange
Member
Post Count: 2105

i see, i hadn't even thought about movement. thanks.

Twitter!
Blog!

Posted 2 years ago #
hajg96
Member
Post Count: 1566

the link doesn't work.

FFA FAN CLUB RANK: HRM!

Posted 2 years ago #
WJUK
The Lone Ranger
Post Count: 13301

Here's the link: link.

Don't click here

Posted 2 years ago #
hajg96
Member
Post Count: 1566

thank you

FFA FAN CLUB RANK: HRM!

Posted 2 years ago #
hajg96
Member
Post Count: 1566

the fla does not work

FFA FAN CLUB RANK: HRM!

Posted 2 years ago #

Private
hajg96
Member
Post Count: 1566

going to sleep, see you soon.
Here it's 21:40.

FFA FAN CLUB RANK: HRM!

Posted 2 years ago #
liphttam1
OMG H4X
Post Count: 5857

Next time use the EDIT button if you wan't to add more.

The button disapeers after an hour though, if it dissapeers you are free to write a new comment.

Remember, easy mode saves lives.

Posted 2 years ago #
Thefox
Member
Post Count: 249

UPDATED FILES!!
Included flash 8 version

Posted 2 years ago #
Nyubis
Nyubis of Strata
Post Count: 9089

Hey, TheFox is back!

Not in cruelty
Not in wrath
the Reaper came today.

An angel visited
this gray path
And took the cube away.

Posted 2 years ago #
DaxterSpeed
DS 2.0
Post Count: 10662

You noticed that right now?

And yeah, apparently he comes back ( /stops lurking) when someone is in trouble with Flash.

DrNeroCF has lurked a lot too. Now he's called Brad... D:

This is a signature!

Posted 2 years ago #
wallross
Member
Post Count: 1729

I have tried to replicate it but i know im doing something wrong. I only upped the speed parameters to 10. My problem is that the keys do not respond to what I have animated. I pratically copied the stuff in your tutorial and just used my own charecter. I named all the instances correctly i just do not know what went wrong.

Posted 2 years ago #
WJUK
The Lone Ranger
Post Count: 13301

Would be good if we could see the code and program in action.

Obviously, when I say "we" I mean people who know AS...

Don't click here

Posted 2 years ago #
wallross
Member
Post Count: 1729

http://www.truploader.com/view/971172

This is the link with my failed slope detector.
It is extremely simmilair to the Fox's, I tweaked the speed parameter.

Posted 2 years ago #

RSS feed for this topic

12 Next »

Reply »

You must log in to post.