2D Fixed Step Logic & Linear Interpolated Time Based Movement

[bigsofty]

Not my code (original by Dmitriy Safro) in BB I think.

Converted for those who may need it.

Cheers,


Ian

Code (glbasic) Select Expand

// --------------------------------- //
// Project: Tween
// Start: Monday, November 01, 2010
// IDE Version: 8.148


// SETCURRENTDIR("Media") // seperate media and binaries?

GLOBAL UPDATE_FREQUENCY% = 10 // times per second
GLOBAL update_time# = 1000 / UPDATE_FREQUENCY%
GLOBAL t% , dt% , execution_time% = 0
GLOBAL oldX%, X%

// boucing ball
GLOBAL dirX# = 1

t = GETTIMERALL()
WHILE NOT KEY(1)
dt = GETTIMERALL() - t
t = GETTIMERALL()

execution_time = execution_time + dt

// fixed interval update loop   
        WHILE execution_time >= update_time
Update()
execution_time = execution_time - update_time
WEND

// calculate the remainder FOR motion interpolation
LOCAL et# = execution_time
LOCAL ut# = update_time
LOCAL tween# = et / ut

Render(tween)
WEND

FUNCTION Update:
// time independent speed
LOCAL Speed# = 150.0 / (1000.0 / update_time) // 150.0 pixels per second

// record the old position for tweening
oldX = X

// move the ball
X = X + (Speed * dirX)

// reverse directions if rect is out of screen bounds
IF X < 0 OR X > 640 THEN dirX = - dirX
ENDFUNCTION

FUNCTION Render: tween#
CLEARSCREEN
// interpolate between old and actual positions
LOCAL tx# = X * tween + oldX * (1.0 - tween)

// draw bouncing ball with interpolated values
DRAWRECT tx - 16 , 50 , 32 , 32, RGB(255,0,0)

// draw second bouncing ball WITHOUT tweening
DRAWRECT X - 16 , 200 , 32 , 32, RGB(0,255,0)

SHOWSCREEN
ENDFUNCTION

[Wampus]

Thanks