opengl order | GameDev.net

ok my problem is i have a cube and i want to have this cube fly around the screen controlled by the user, the user can rotate the cube and make it fly in any direction they want, my problem is that my cube is always rotating around the center of the screen instead of its center, now i know what your gonna say, your gonna say well thats easy your simply translating first and then rotating, AHA but i am not i am rotating first and then translating but opengl doesn''t seem to understant what the hell i am telling it, in my drawing code i AM rotating before translating but opengl is not it seems to do whatever it wants and its translating and THEN rotating = bad because my "cube" is always rotating around the center of the screen, how can i solve this? in a nutshell my code looks like this: glLoadIdentity(); glRotatef(zrot,0.0f,0.0f,1.0f); glTranslatef(x,y,-25.0f); glBegin(GL_QUADS); . . .

This is taken straight from "OpenGL Superbible SE" by Waite Group Press.
I''m not employed or in any way associated with them, but this book
is AMAZING. Try this:



	// Camera initial position and orientation
	// Initially at Origin, slightly above the ground
	cameraData.position[0] = 0.0f;	
	cameraData.position[1] = -0.2f;
	cameraData.position[2] = -3.0f;

	// Looking down negative Z Axis (North). Positive X is to the right
	cameraData.orientation[0] = 0.0f;
	cameraData.orientation[1] = 0.0f;
	cameraData.orientation[2] = 0.0f;




void UpdatePosition(struct CAMERA *pCamera)
	{
	float fLinearVelocity = 0.0f;
	float fAngularVelocityY = 0.0f;
	float fAngularVelocityX = 0.0f;
	float fAngularVelocityZ = 0.0f;
	float fTime,fAngle,fXDelta,fZDelta;
	JOYINFO ji;
	LARGE_INTEGER currentTime;

	// Check Joystick if present
	if(joyGetPos(JOYSTICKID1, &ji) == JOYERR_NOERROR)
		{
		// Button 1 moves forward, button 2 moves backwards
		if(ji.wButtons & JOY_BUTTON1)
			fLinearVelocity = 0.8f;

		if(ji.wButtons & JOY_BUTTON2)
			fLinearVelocity = -0.8f;

		// Check for spin left/right (Y Axis rotation)
		// Move quicker if joystick is moved hard
		if(ji.wXpos < 20000)
			fAngularVelocityY = -15.0f;
		if(ji.wXpos < 3000)
			fAngularVelocityY = -22.0f;

		if(ji.wXpos > 45536)
			fAngularVelocityY = 15.0f;
		if(ji.wXpos > 62536)
			fAngularVelocityY = 22.0f;

		// Check for looking up and down
		if(ji.wYpos < 20000)
			fAngularVelocityX = 14.0f;
		if(ji.wYpos < 3000)
			fAngularVelocityX = 21.0f;
		
		if(ji.wYpos > 45536)
			fAngularVelocityX = -14.0f;
		if(ji.wYpos > 63536)
			fAngularVelocityX = - 21.0f;
		}


	// Keyboard Input
	// Check for forward or backwards Motion
	if(GetAsyncKeyState(VK_UP))
		fLinearVelocity = 0.8f;

	if(GetAsyncKeyState(VK_DOWN))
		fLinearVelocity = -0.8f;

	// Check for spin left/right (Y Axis rotation)
	if(GetAsyncKeyState(VK_LEFT))
		fAngularVelocityY = -14.0f;

	if(GetAsyncKeyState(VK_RIGHT))
		fAngularVelocityY = 14.0f;

	// Check for looking up and down
	if(GetAsyncKeyState(0x41))		// A key
		fAngularVelocityX = 14.0f;
	
	if(GetAsyncKeyState(0x5a))		// Z key
		fAngularVelocityX = -14.0f;


	// Adjust position and orientation. Get the time since the last
	// check. If the velocity = 0 (no keypress or mouse movement)
	// then the motion will be nil...
	// D = vt
	QueryPerformanceCounter(&currentTime);
	fTime = (float)(currentTime.QuadPart - lastTime.QuadPart)/
				(float)timerFrequency.QuadPart;
	lastTime = currentTime;

	// Update Rotation angles (clamp the X rotation)
	fAngle = fTime * fAngularVelocityX;
	fAngle += pCamera->orientation[0];

	if((fAngle < 90.0f) && (fAngle > -90.0f))
		pCamera->orientation[0] = fAngle;

	pCamera->orientation[1] += fTime * fAngularVelocityY;
	
	// Update linear position
	fTime = fTime * fLinearVelocity;
	fXDelta = fTime * (float)(sin(DEGTORAD(pCamera->orientation[1])));
	fXDelta += pCamera->position[0];
	fZDelta = fTime * (float)(cos(DEGTORAD(pCamera->orientation[1])));
	fZDelta += pCamera->position[2];


	pCamera->position[0] = fXDelta;
	pCamera->position[2] = fZDelta;

	// Halt the camera at the boundaries of the Virtual World.
	// The maximum range for the person is +/- 95 from the center
	// The boundaries of the world are +/- 100 in all directions
	if(pCamera->position[0] > 95.0f)
		pCamera->position[0] = 95.0f;

	if(pCamera->position[0] < -95.0f)
		pCamera->position[0] = -95.0f;

	if(pCamera->position[2] > 95.0f)
		pCamera->position[2] = 95.0f;

	if(pCamera->position[2] < -95.0f)
		pCamera->position[2] = -95.0f;
	}

void PositionCamera()
{
glLoadIdentity();	// Z-X-Y (Boom specific)

		glRotatef(cameraData.orientation[2], 0.0f, 0.0f, 1.0f);
		glRotatef(cameraData.orientation[0], 1.0f, 0.0f, 0.0f);
		glRotatef(cameraData.orientation[1], 0.0f, 1.0f, 0.0f);
		glTranslatef(-cameraData.position[0],cameraData.position[1],cameraData.position[2]);
}

I know its for a camera, but it works for cubes as well. Hope that helps

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