Thread: Jumping Script

I'm pretty crappy with programming games, but here's a little jumping script I made. Don't pay much attention to DrawGLScene(), because it doesn't really have much to do with the script to make the character jump. glCreateQuad() isn't defined in this code either, but it just creates a simple square.

Code:

float xpos=0; // x position
float MaxJump=1.5; // max height of jump
float Gravity=1.05; // manipulates max jump
float SubMaxJump=MaxJump; //constant that restores MaxJump
float y=0; // Y position
float yOrigin=y; // Constant that restores y back to it's origin
bool Jumping=false; //Jumping flag
bool Falling=false; //Falling flag
bool JumpOK=true; //Is it okay to jump?

int DrawGLScene(GLvoid)
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	glLoadIdentity();
	glTranslatef(xpos,y,-10);
	glColor3f(0.7f,0.0f,0.0f);

	glCreateQuad();
	
	KeyControls();

	return TRUE;
}

bool move;

void KeyControls()
{
if(keys[VK_RIGHT])
xpos += .05;
if(keys[VK_LEFT])
xpos -= .05;

/*if you press UP, you're not jumping or falling, and it's okay to jump, make Jumping=true, and JumpOK=false*/

if(keys[VK_UP] && !Jumping && !Falling && JumpOK)
{
Jumping=true;
JumpOK=false;
}

/*If yo're jumping, divide MaxJump by Gravity so it will slowly get smaller, and add MaxJump to y so the character moves up*/
if(Jumping)
{
	MaxJump /= Gravity;
	y += MaxJump;
}

/*If MaxJump has run out, our character is no longer jumping, but falling*/
if(MaxJump <= 0)
{
	Falling=true;
	Jumping=false;
}

/*Opposite of Jumping*/
if(Falling)
{
	MaxJump *= Gravity;
	y -= MaxJump;
}

/*Keeps MaxJump from getting higher than 4, so the character doesn't fall at large intervals.*/
if(Falling && MaxJump > 3)
MaxJump = 4;

/*If the block is back to it's y origin, make both jumping and falling false, and assign MaxJump to constant SubMaxJump to restore it back to normal. It's not okay to jump again unless you release the UP key, and then press it again.*/
if(y <= yOrigin)
{
	Jumping=false;
	Falling=false;
	MaxJump=SubMaxJump;
	if(keys[VK_UP]==false)
		JumpOK=true;
}
}

What do you think? It's definitely far from perfect, but it does sorta work. Any tips you have to make more efficient jumping code?

And we care that you made a jump script?

Originally posted by dbgt goten
More realisticly you might not be jumping from from 0 y position. Not all games, in fact very little, have flat playing fields.

Also, the max jump variable is a little redundent. Rather you should use your gravity variable along with a jump velocity to determine max height, it will also make the jump more fluid and believable.

Heres some vague code you might want to consider to improve your script.

Code:

struct sVelocity  {
     float x,y,z;
}
typdef enum PLAYER_STATE { PS_NONE, PS_JUMPING, PS_JUMPING2, PS_FALLING, PS_FIRING, PS_ETC } // jumping2 state could be used for double jumping
sVelocity gravity = { 0.0f, -9.8f, 0.0f }; // 9.8 newtons = gravity on earth (probably will be adjusted for game sake to say 0.98)
// gravity is always used to keep player on the ground
sVelocity jumpVelocity = { 0.0f, 27.3f, 0.0f }; 

// in game loop
player.velocity += gravity; // take current velocity including new movement commands from the keyboard/mouse and add in gravity. this operator wont work, willhave to do it manualy.

// after detecting the user wants to jump (via keyboard press)
if( player.onGroundSurface() && player.state == PS_NONE ) {
     player.state = PS_JUMPING;
     player.velocity *= jumpVelocity; // figure in jumping momentum;
}


// after all the velocitys have been added together, you are left with the net velocity. This will determine the players next location
if( !CheckCollision( player.velocity ) ) {
      player.x += velocity.x;
      player.y += velocity.y;
      player.z += velocity.z;
} else {
      player.x = snapToCollisionSurface(player.velocity).x 
      player.y = snapToCollisionSurface(player.velocity).y;
      player.z = snapToCollisionSurface(player.velocity).z;
}
// this set of collision functions uses a collision method of detecting if moving from current position
// to the next position (figured from sent velocity) if there will be a collision with a surface, if so we get the point of the surface we will colide with, and snap our position right to it.

Hope this helps a little.

I don't really understand that too well...I'm not very experienced with C++ or OpenGL or game programming in general. I was just wondering if my method for programming jumps was good or not.