creating a platform game in as3 part 4

In the end of the last post we had a problem where the character vibrated. This was because when ever the character touched the floor i made it move up by one pixel. to rectify this i will make another hittest that detects when the character is one pixel off the floor and only calculate the velocity of the player if it returns false.

Some code:-

function run(event:Event) {
velocity+=gravity;
if (land.hitTestPoint(char.x, char.y+char.height/2, true)) {
velocity = 0;
char.y--
}
if (!land.hitTestPoint(char.x, char.y+char.height/2+1, true)) {
char.y += velocity;
} else {
velocity=0;
if (attemptJump==true) {
char.y--;
velocity =-5;
}
}
if (goleft==true) {
char.x+=lspeed;
}
if (goright==true) {
char.x+=rspeed;
}
}

This is only the new run function because that's all i have changed.

I have removed the else statement that i created last time to calculate the velocity and moved it to the new hitTest where i calculate if the character hits one pixel above the land.

The other thing that i have changed is to move the attemptjump function to the new hitTest and add to it another char.y-- which means that the character will be able to jump with the new hitTest in place.

Heres a demo.

Ok thats that problem fixed. Now i have noticed that when you walk into a steep wall, you seem to go into it for a bit and then float to the top if you stop. To fix this we can make it so that you can't walk up steep hills. We can do this 2 ways, either by creating 2 more  movieClips, 1 either side of the character and calculating the gradient in between them. Or we can use the hitTestPoint function again and use it to calculate a point that stops the player moving if the hill is too steep. i have chosen the latter because it is easier and will run quicker.

First we need to change the land movieClip so that it has some steep hills at either side of the screen. 

Next we have to create the new hitTest functions. 

some code, just the new run function again.

function run(event:Event) {
velocity+=gravity;
if (land.hitTestPoint(char.x, char.y+char.height/2, true)) {
velocity = 0;
char.y--;
}
if (!land.hitTestPoint(char.x, char.y+char.height/2+1, true)) {
char.y += velocity;
} else {
velocity=0;
if (attemptJump==true) {
char.y--;
velocity =-5;
}
}
if (!land.hitTestPoint(char.x-char.width/2, char.y+char.height/4, true)) {
if (goleft==true) {
char.x+=lspeed;
}
}
if (!land.hitTestPoint(char.x+char.width/2, char.y+char.height/4, true)) {
if (goright==true) {
char.x+=rspeed;
}
}
}

As you can see from the code i have put the new hitTest functions in front of the move left and right functions. Lets look at the first one, the "goleft" function. i have put a conditional statement in front of the old goleft function. Note the exclamation mark in front. This means that you can go left only if the character's left hand side, a quarter up from the foot, is not touching the land. 

It is nearly the same code for the goright function, but if look carefully, you will see that instead of a "char.x-char.width/2" we have a "char.x+char.width/2" this is just declaring a point on the right side instead of the left.

Heres a demo

As you can see, the demo runs fine, you can't walk up steep hills but you can still jump up them. Thats fine for now.

In the next tutorial i am going to see what happens if i add a floating platform that you can go underneath and jump on to.