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OpenGL Camera following object


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#1 Sczerzuja   Members   -  Reputation: 108

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Posted 17 January 2014 - 10:33 AM

Im creating a minigame something like RPG and i want to make camera that follow my character.My problem is that object "postac" is moving forward and backward with camera correctly but when i want to look left or right i doesnt change what im doing wrong ?How to use this rotatef function or what to change pls help me. If u want to check how it works download and run zegar.exe file from my dropbox a

https://www.dropbox.com/sh/wmywu1xqji7dmvn/0lSi2pJO1r

void Display()
{
glClearColor (0.0,0.0,0.0,1.0);
if (deltaMove)
computePos(deltaMove);
if (deltaAngle)
computeDir(deltaAngle);
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);

glLoadIdentity();

gluLookAt( x, 1.0f, z,
x+lx, 1.0f, z+lz,
0.0f, 1.0f, 0.0f);

glTranslatef( 0, -40, -10 ) ;
niebo();
makieta();
glPushMatrix() ;
glTranslatef( x+lx, 1.0f, z+lz ) ;
glRotatef(angle,x+lx, 1.0, z+lz ) ;

postac();
glPopMatrix() ;

glutSwapBuffers();
}


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#2 McGrane   Members   -  Reputation: 827

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Posted 17 January 2014 - 10:56 AM

Hi, 

I'm not sure exactly how your lx and lz are being changed, but if you want to rotate a point, and know where it actually is, you should do so using a rotation matrix. You should have a point as what you are looking at, and then rotate it around your character - as far as i can tell, you are just rotating the world around using glRotatef. Another advantage to rotating a point is that you can then easily change the direction of your character to walk towards it, while glRotate will not necessarily allow you to do this.

Have a look here for an explanation of rotation matrix http://en.wikipedia.org/wiki/Rotation_matrix or just Google them.

Note: The thing that caught me the first few times with opengl is that when using the math lib for cos an sin - that it uses radian's .. not degrees ! Keep this in mind 


Edited by McGrane, 17 January 2014 - 11:00 AM.


#3 Sczerzuja   Members   -  Reputation: 108

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Posted 17 January 2014 - 12:20 PM

Here is another part of my code. How to use it in my code ? Im rdy newbie and i need to finish that to tomorrow ill be very glad if u show me what change i did a lot but this only 1 thing is missing ;/

void computePos(float deltaMove) {

	x += deltaMove * lx * 0.1f;
	z += deltaMove * lz * 0.1f;
}

void computeDir(float deltaAngle) {

	angle += deltaAngle;
	lx = sin(angle);
	lz = -cos(angle);
}


void pressKey(int key, int xx, int yy) {

	switch (key) {
		case GLUT_KEY_LEFT : deltaAngle = -0.005f; break;
		case GLUT_KEY_RIGHT : deltaAngle = 0.005f; break;
		case GLUT_KEY_UP : deltaMove = 0.5f; break;
		case GLUT_KEY_DOWN : deltaMove = -0.5f; break;
	}
}

void releaseKey(int key, int x, int y) {

	switch (key) {
		case GLUT_KEY_LEFT : deltaAngle = 0.0f;break;
		case GLUT_KEY_RIGHT : deltaAngle = 0.0f;break;
		case GLUT_KEY_UP : deltaMove = 0;break;
		case GLUT_KEY_DOWN : deltaMove = 0;break;
	}
}

Edited by Sczerzuja, 17 January 2014 - 12:46 PM.


#4 Sczerzuja   Members   -  Reputation: 108

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Posted 18 January 2014 - 10:45 AM

any ideas ?



#5 JoryRFerrell2013   Members   -  Reputation: 175

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Posted 20 January 2014 - 11:41 PM

You can create a tracker for each obj, recording it's absolute global position. For the object you want to follow, simply subtract the vector of the distance and rotation you want relative to the object, and this will have you "follow" the object.


Edited by JoryRFerrell2013, 20 January 2014 - 11:41 PM.





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