Help to correct the code - GameCreators Forum

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Gary1234

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Joined: 22nd Sep 2011

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Posted: 25th Sep 2011 06:16

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The following are the code to approximate the motion of falling object. However the Object does not move...

I have shown the "time" and the "distance" at the top right of the screen. The time is run, but the distance stop at 0....
Can anyone help me to correct it?
(i am using Visual Studio2008)

+ Code Snippet

#include "DarkGDk.h"

const int RefreshRate = 60;
const int Acceleration = 0.98;


void DarkGDK()
{
	int ball1x, ball1y, ball2x, ball2y;
	int time = 0;
	float distance;

	void setup();

	int maxY = dbScreenHeight() - 50;

	ball2y = 100;
	ball2x = dbScreenWidth() / 2 +50;

	ball1y = 0;
	ball1x = dbScreenWidth() / 2 -50;

	dbSyncOn();
	dbSyncRate(RefreshRate);

	while (LoopGDK())
	{ 
		dbCLS();

		const DWORD RED = dbRGB(255,0,0);
		const DWORD BLACK = dbRGB(0,0,0);

		dbInk(RED,BLACK);
		dbBox( ball1x, ball1y, ball2x, ball2y);
		dbPrint(dbStr(time));



		if (ball2y < maxY)
		{
			

			distance =  0.5 * Acceleration * time * time;

			ball1y = distance;
			ball2y += distance;

			dbPrint(dbStr(distance));

			dbLine(0,ball1y,100,ball1y);



			time++;
		}
		else
		{
			ball2y = maxY;
			ball1y = maxY - 100;
		}



		dbSync();
	
	}

}

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Mireben

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Joined: 5th Aug 2008

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Posted: 25th Sep 2011 10:40 Edited at: 25th Sep 2011 10:44

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+ Code Snippet

const int Acceleration = 0.98;

Make that a float. If it's int, it's zero (the integer part of 0.98). So you are always multiplying with zero.

You should also correct the calculation of the first y coordinate to += not only = otherwise the box will stretch.

+ Code Snippet

ball1y += distance;

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Gary1234

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Joined: 22nd Sep 2011

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Posted: 25th Sep 2011 13:31

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Thinkyou again for you kindly help~!!!

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Gary1234

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Joined: 22nd Sep 2011

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Posted: 28th Sep 2011 07:53

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I have changed a bit of the program...and ...it does not work again...Would you please have a look?

The objective of the programme change to approximate the motion of object with acceleration and deceleration.

The odject will accelerate until travelling distance = 300,
and change to deceleration at constant rate. The object will stop at velocity = 0.

I am not sure which part is wrong....

#include "DarkGDk.h"

void DackGDK()
{
	dbSetDisplayMode(700,300,dbScreenDepth());
	dbSetWindowTitle("Moving Box With Acceleration and Deceleration");

const float Acceleration = 0.1;
	const float Deceleration = 0.1;
	const int RefreshRate = 60;
	const int StartToDecelerate = 300;

int box1x, box1y, box2x, box2y;
	int Time = 0;
	float TravelDistance = 0;
	float TravelVelocity = 0;

box2x = 25;
	box2y = dbScreenHeight() /2 + 5;
	box1x = 15;
	box1y = dbScreenHeight() /2 - 5;

dbSyncOn();
	dbSyncRate(RefreshRate);

while (LoopGDK())
	{ 
		dbCLS();

const DWORD RED = dbRGB(255,0,0);
		const DWORD BLACK = dbRGB(0,0,0);

dbInk(RED,BLACK);
		dbBox( box1x, box1y, box2x, box2y);
		dbPrint(dbStr(TravelDistance));
		dbPrint(dbStr(Time));

if (TravelDistance < StartToDecelerate)
		{
			TravelVelocity = Acceleration * Time;
			TravelDistance = Acceleration * Time * Time /2;
			box2x += TravelDistance;
			box1x += TravelDistance;
			Time ++;		
		}
		else if (TravelVelocity > 0)
		{
			Time = 0;
			
			TravelVelocity -= (Deceleration * Time);
		
			TravelDistance += (TravelVelocity * Time - Deceleration * Time * Time /2);

box2x += TravelDistance;
			box1x += TravelDistance;
			Time ++;
		}
		else
		{
			box2x = TravelDistance;
			box1x = TravelDistance;
		}
	dbSync();
	}
}

+ Code Snippet

#include "DarkGDk.h"

void DackGDK()
{
	dbSetDisplayMode(700,300,dbScreenDepth());
	dbSetWindowTitle("Moving Box With Acceleration and Deceleration");

	const float Acceleration = 0.1;
	const float Deceleration = 0.1;
	const int RefreshRate = 60;
	const int StartToDecelerate = 300;

	int box1x, box1y, box2x, box2y;
	int Time = 0;
	float TravelDistance = 0;
	float TravelVelocity = 0;


	box2x = 25;
	box2y = dbScreenHeight() /2 + 5;
	box1x = 15;
	box1y = dbScreenHeight() /2 - 5;

	dbSyncOn();
	dbSyncRate(RefreshRate);


	while (LoopGDK())
	{ 
		dbCLS();

		const DWORD RED = dbRGB(255,0,0);
		const DWORD BLACK = dbRGB(0,0,0);

		dbInk(RED,BLACK);
		dbBox( box1x, box1y, box2x, box2y);
		dbPrint(dbStr(TravelDistance));
		dbPrint(dbStr(Time));

		
		if (TravelDistance < StartToDecelerate)
		{
			TravelVelocity = Acceleration * Time;
			TravelDistance = Acceleration * Time * Time /2;
			box2x += TravelDistance;
			box1x += TravelDistance;
			Time ++;		
		}
		else if (TravelVelocity > 0)
		{
			Time = 0;
			
			TravelVelocity -= (Deceleration * Time);
		
			TravelDistance += (TravelVelocity * Time - Deceleration * Time * Time /2);

			box2x += TravelDistance;
			box1x += TravelDistance;
			Time ++;
		}
		else
		{
			box2x = TravelDistance;
			box1x = TravelDistance;
		}
	dbSync();
	}
}

The system has the following output:

1>------ Build started: Project: Dark GDK - Moving Object with A D, Configuration: Debug Win32 ------
1>Compiling...
1>Main.cpp
1>Linking...
1>darksdk.lib(DarkSDK.obj) : error LNK2019: unresolved external symbol "void __cdecl DarkGDK(void)" (?DarkGDK@@YAXXZ) referenced in function _WinMain@16

1>Debug\Dark GDK - Moving Object with A D.exe : fatal error LNK1120: 1 unresolved externals

1>Build log was saved at "file://c:\Users\Win 7 User\Documents\Visual Studio 2008\Projects\Dark GDK - Moving Object with A D\Dark GDK - Moving Object with A D\Debug\BuildLog.htm"

1>Dark GDK - Moving Object with A D - 2 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

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Mr Bigglesworth

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Joined: 4th Mar 2008

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Posted: 28th Sep 2011 16:26

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Quote: "void DackGDK()"

You wrote your entry point wrong, it is misspelled.

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Dark GDK / Help to correct the code