as3 slope detection for non uniform terrains - actionscript-3

Question

I want to create a 2d game in which a car moves along the edge of an irregular shaped hill. I want to use basic as3 (no physics engine like Box2d or Nape). With a lot of research I found this thing which is exactly what i want but there is only the logic and no source code. Can someone help me with a piece of code that can do this in as3? Also suggest if there is a better alternative to get the desired output.

Answer 1

I myself don't have much knowledge into code like this, and I can't make a comment because I'm short 7 reputation :'( but the article you linked does have another link to a Worms-esque program with code that might be of help to you. Here's a link to that site in question and I'll also provide some appropriate code that you can see if it's of use to you.
So this program has a listener for if any key is down and sets a boolean as true if it's a key your program is using (movement, space for jumping or whatever), that listener looks like this
public function key_down(e:KeyboardEvent) {
if (e.keyCode==37) {
left_key=true;
}
if (e.keyCode==39) {
right_key=true;
}
if (e.keyCode==32) {
space_key=true;
}
}
And then it has a subsequent listener for when a key is released
public function key_up(e:KeyboardEvent) {
if (e.keyCode==37) {
left_key=false;
}
if (e.keyCode==39) {
right_key=false;
}
if (e.keyCode==32) {
space_key=false;
}
}
And finally the stage has an ENTER_FRAME listener for moving the character that runs this function
public function move_character(e:Event) {
//If left key is pressed, we'll move the character to the left
if (left_key) {
for (i=0; i<3; i++) {//Do you remember when we made the character fall? We had to move the character pixel by pixel
if (! terrain_bmpd.hitTest(new Point(terrain_bmp.x,terrain_bmp.y),0x01,new Rectangle(character.x-6,character.y-10,1,17))) {
character.x--; /*If the character doesn't hit the ground, we can move left. However,
the character may be sunk under the ground. We have to lift it*/
while (terrain_bmpd.hitTest(new Point(terrain_bmp.x,terrain_bmp.y),0x01,new Rectangle(character.x-5,character.y+9,10,1))) {
character.y--;
}
}
}
}
if (right_key) {//Well, that's the same for the right key
for (i=0; i<3; i++) {
if (! terrain_bmpd.hitTest(new Point(terrain_bmp.x,terrain_bmp.y),0x01,new Rectangle(character.x+5,character.y-10,1,17))) {
character.x++;
while (terrain_bmpd.hitTest(new Point(terrain_bmp.x,terrain_bmp.y),0x01,new Rectangle(character.x-5,character.y+9,10,1))) {
character.y--;
}
}
}
}
if (space_key&&! jumping) {//That's easy: if he isn't jumping and you press space, his speed will be negative and he'll jump
character_speed=-10;
jumping=true;//Now the character can't jump again
}
character_speed++;//Every frame we will increase character's speed
if (character_speed>0) {
//If the speed is positive, we will check a collision between the terrain and the rectangle below the character
for (i=0; i<character_speed; i++) {//We check the collision pixel by pixel...
if (! terrain_bmpd.hitTest(new Point(terrain_bmp.x,terrain_bmp.y),0x01,new Rectangle(character.x-5,character.y+9,10,1))) {
character.y++;//If there isn't a collision, the character will fall
} else {
jumping=false;//If there's a collision with the ground, the character isn't jumping
character_speed=0;//The speed is 0, because the character hit the ground
}
}
} else {
for (i=0; i<Math.abs(character_speed); i++) {//If the speed is negative, the for loop won't work. We have to use Math.abs().
//Now we will check the collision between the terrain and the rectangle above the character
if (! terrain_bmpd.hitTest(new Point(terrain_bmp.x,terrain_bmp.y),0x01,new Rectangle(character.x-5,character.y-10,10,1))) {
character.y--;
} else {
character_speed=0;//Well, that's the same: the character hit the ground
}
}
}
}
Sorry I couldn't provide any personal experience, if you want more then the article I linked above will provide more information.