FPS camera scene node fix

Geomaster · Post by **Geomaster** » Sat Apr 10, 2010 10:39 pm

I saw that many of us use Irrlicht's built in FPS camera. But there's a small mistake in the animator which controls it...

So, here's how the movement looks like:

(where blue is ahead, red is strafing, and step is the number of units the camera should move per frame)

And everything is just fine, until we take a look at the diagonal movement:

Here, both X and Z axis are incremented by step (see the vectors in the second picture). The vector for diagonal movement is marked green, and it's length is marked as x.
So, according to a simple Pythagoras's theorem, x equals...

That means that diagonal movement (x) is sqrt(2) [~1.41421...] times faster than straight. Which means that when moving diagonally, one has an advantage.
So, here's the solution. For diagonal movement, let's say we have to increment both components (X and Z, Y not taken into account here due to nature of moving) for a value y.
So, if x has to equal step as well (to make moving in each direction equally fast), then we have:

Both components should be increased for step / sqrt(2) for diagonal movement to equal Step.

So, when moving diagonally, we should have this:

So I fixed a couple of things in Irrlicht about this. Just replace the code in CSceneNodeAnimatorCameraFPS.cpp with this (NOTE: this should apply for 1.7, not sure about the others, but there should be no problems):

Code: Select all

// Copyright (C) 2002-2009 Nikolaus Gebhardt
// This file is part of the "Irrlicht Engine".
// For conditions of distribution and use, see copyright notice in irrlicht.h

#include "CSceneNodeAnimatorCameraFPS.h"
#include "IVideoDriver.h"
#include "ISceneManager.h"
#include "Keycodes.h"
#include "ICursorControl.h"
#include "ICameraSceneNode.h"
#include "ISceneNodeAnimatorCollisionResponse.h"

#define SQRT2 1.4142135623730950488016887242097

namespace irr
{
namespace scene
{

//! constructor
CSceneNodeAnimatorCameraFPS::CSceneNodeAnimatorCameraFPS(gui::ICursorControl* cursorControl,
		f32 rotateSpeed, f32 moveSpeed, f32 jumpSpeed,
		SKeyMap* keyMapArray, u32 keyMapSize, bool noVerticalMovement, bool invertY)
: CursorControl(cursorControl), MaxVerticalAngle(88.0f),
	MoveSpeed(moveSpeed), RotateSpeed(rotateSpeed), JumpSpeed(jumpSpeed),
	MouseYDirection(invertY ? -1.0f : 1.0f),
	LastAnimationTime(0), firstUpdate(true), NoVerticalMovement(noVerticalMovement)
{
	#ifdef _DEBUG
	setDebugName("CCameraSceneNodeAnimatorFPS");
	#endif

	if (CursorControl)
		CursorControl->grab();

	allKeysUp();

	// create key map
	if (!keyMapArray || !keyMapSize)
	{
		// create default key map
		KeyMap.push_back(SCamKeyMap(EKA_MOVE_FORWARD, irr::KEY_UP));
		KeyMap.push_back(SCamKeyMap(EKA_MOVE_BACKWARD, irr::KEY_DOWN));
		KeyMap.push_back(SCamKeyMap(EKA_STRAFE_LEFT, irr::KEY_LEFT));
		KeyMap.push_back(SCamKeyMap(EKA_STRAFE_RIGHT, irr::KEY_RIGHT));
		KeyMap.push_back(SCamKeyMap(EKA_JUMP_UP, irr::KEY_KEY_J));
	}
	else
	{
		// create custom key map
		setKeyMap(keyMapArray, keyMapSize);
	}
}


//! destructor
CSceneNodeAnimatorCameraFPS::~CSceneNodeAnimatorCameraFPS()
{
	if (CursorControl)
		CursorControl->drop();
}


//! It is possible to send mouse and key events to the camera. Most cameras
//! may ignore this input, but camera scene nodes which are created for
//! example with scene::ISceneManager::addMayaCameraSceneNode or
//! scene::ISceneManager::addFPSCameraSceneNode, may want to get this input
//! for changing their position, look at target or whatever.
bool CSceneNodeAnimatorCameraFPS::OnEvent(const SEvent& evt)
{
	switch(evt.EventType)
	{
	case EET_KEY_INPUT_EVENT:
		for (u32 i=0; i<KeyMap.size(); ++i)
		{
			if (KeyMap[i].keycode == evt.KeyInput.Key)
			{
				CursorKeys[KeyMap[i].action] = evt.KeyInput.PressedDown;
				return true;
			}
		}
		break;

	case EET_MOUSE_INPUT_EVENT:
		if (evt.MouseInput.Event == EMIE_MOUSE_MOVED)
		{
			CursorPos = CursorControl->getRelativePosition();
			return true;
		}
		break;

	default:
		break;
	}

	return false;
}


void CSceneNodeAnimatorCameraFPS::animateNode(ISceneNode* node, u32 timeMs)
{
	if (!node || node->getType() != ESNT_CAMERA)
		return;

	ICameraSceneNode* camera = static_cast<ICameraSceneNode*>(node);

	if (firstUpdate)
	{
		camera->updateAbsolutePosition();
		if (CursorControl && camera)
		{
			CursorControl->setPosition(0.5f, 0.5f);
			CursorPos = CenterCursor = CursorControl->getRelativePosition();
		}

		LastAnimationTime = timeMs;

		firstUpdate = false;
	}

	// If the camera isn't the active camera, and receiving input, then don't process it.
	if(!camera->isInputReceiverEnabled())
		return;

	scene::ISceneManager * smgr = camera->getSceneManager();
	if(smgr && smgr->getActiveCamera() != camera)
		return;

	// get time
	f32 timeDiff = (f32) ( timeMs - LastAnimationTime );
	LastAnimationTime = timeMs;

	// update position
	core::vector3df pos = camera->getPosition();

	// Update rotation
	core::vector3df target = (camera->getTarget() - camera->getAbsolutePosition());
	core::vector3df relativeRotation = target.getHorizontalAngle();

	if (CursorControl)
	{
		if (CursorPos != CenterCursor)
		{
			relativeRotation.Y -= (0.5f - CursorPos.X) * RotateSpeed;
			relativeRotation.X -= (0.5f - CursorPos.Y) * RotateSpeed * MouseYDirection;

			// X < MaxVerticalAngle or X > 360-MaxVerticalAngle

			if (relativeRotation.X > MaxVerticalAngle*2 &&
				relativeRotation.X < 360.0f-MaxVerticalAngle)
			{
				relativeRotation.X = 360.0f-MaxVerticalAngle;
			}
			else
			if (relativeRotation.X > MaxVerticalAngle &&
				relativeRotation.X < 360.0f-MaxVerticalAngle)
			{
				relativeRotation.X = MaxVerticalAngle;
			}

			// Do the fix as normal, special case below
			// reset cursor position to the centre of the window.
			CursorControl->setPosition(0.5f, 0.5f);
			CenterCursor = CursorControl->getRelativePosition();

			// needed to avoid problems when the event receiver is disabled
			CursorPos = CenterCursor;
		}

		// Special case, mouse is whipped outside of window before it can update.
		video::IVideoDriver* driver = smgr->getVideoDriver();
		core::vector2d<u32> mousepos(u32(CursorControl->getPosition().X), u32(CursorControl->getPosition().Y));
		core::rect<u32> screenRect(0, 0, driver->getScreenSize().Width, driver->getScreenSize().Height);

		// Only if we are moving outside quickly.
		bool reset = !screenRect.isPointInside(mousepos);

		if(reset)
		{
			// Force a reset.
			CursorControl->setPosition(0.5f, 0.5f);
			CenterCursor = CursorControl->getRelativePosition();
			CursorPos = CenterCursor;
 		}
	}

	// set target

	target.set(0,0, core::max_(1.f, pos.getLength()));
	core::vector3df movedir = target;

	core::matrix4 mat;
	mat.setRotationDegrees(core::vector3df(relativeRotation.X, relativeRotation.Y, 0));
	mat.transformVect(target);

	if (NoVerticalMovement)
	{
		mat.setRotationDegrees(core::vector3df(0, relativeRotation.Y, 0));
		mat.transformVect(movedir);
	}
	else
	{
		movedir = target;
	}

	movedir.normalize();

	float MS = MoveSpeed;

	if ((CursorKeys[EKA_MOVE_FORWARD] || CursorKeys[EKA_MOVE_BACKWARD])
									&&
		(CursorKeys[EKA_STRAFE_LEFT] || CursorKeys[EKA_STRAFE_RIGHT]))
			MS /= SQRT2;

	if (CursorKeys[EKA_MOVE_FORWARD])
		pos += movedir * timeDiff * MS;

	if (CursorKeys[EKA_MOVE_BACKWARD])
		pos -= movedir * timeDiff * MS;

	// strafing

	core::vector3df strafevect = target;
	strafevect = strafevect.crossProduct(camera->getUpVector());

	if (NoVerticalMovement)
		strafevect.Y = 0.0f;

	strafevect.normalize();

	if (CursorKeys[EKA_STRAFE_LEFT])
		pos += strafevect * timeDiff * MS;

	if (CursorKeys[EKA_STRAFE_RIGHT])
		pos -= strafevect * timeDiff * MS;

	// For jumping, we find the collision response animator attached to our camera
	// and if it's not falling, we tell it to jump.
	if (CursorKeys[EKA_JUMP_UP])
	{
		const ISceneNodeAnimatorList& animators = camera->getAnimators();
		ISceneNodeAnimatorList::ConstIterator it = animators.begin();
		while(it != animators.end())
		{
			if(ESNAT_COLLISION_RESPONSE == (*it)->getType())
			{
				ISceneNodeAnimatorCollisionResponse * collisionResponse =
					static_cast<ISceneNodeAnimatorCollisionResponse *>(*it);

				if(!collisionResponse->isFalling())
					collisionResponse->jump(JumpSpeed);
			}

			it++;
		}
	}

	// write translation
	camera->setPosition(pos);

	// write right target
	target += pos;
	camera->setTarget(target);
}


void CSceneNodeAnimatorCameraFPS::allKeysUp()
{
	for (u32 i=0; i<6; ++i)
		CursorKeys[i] = false;
}


//! Sets the rotation speed
void CSceneNodeAnimatorCameraFPS::setRotateSpeed(f32 speed)
{
	RotateSpeed = speed;
}


//! Sets the movement speed
void CSceneNodeAnimatorCameraFPS::setMoveSpeed(f32 speed)
{
	MoveSpeed = speed;
}


//! Gets the rotation speed
f32 CSceneNodeAnimatorCameraFPS::getRotateSpeed() const
{
	return RotateSpeed;
}


// Gets the movement speed
f32 CSceneNodeAnimatorCameraFPS::getMoveSpeed() const
{
	return MoveSpeed;
}


//! Sets the keyboard mapping for this animator
void CSceneNodeAnimatorCameraFPS::setKeyMap(SKeyMap *map, u32 count)
{
	// clear the keymap
	KeyMap.clear();

	// add actions
	for (u32 i=0; i<count; ++i)
	{
		switch(map[i].Action)
		{
		case EKA_MOVE_FORWARD: KeyMap.push_back(SCamKeyMap(EKA_MOVE_FORWARD, map[i].KeyCode));
			break;
		case EKA_MOVE_BACKWARD: KeyMap.push_back(SCamKeyMap(EKA_MOVE_BACKWARD, map[i].KeyCode));
			break;
		case EKA_STRAFE_LEFT: KeyMap.push_back(SCamKeyMap(EKA_STRAFE_LEFT, map[i].KeyCode));
			break;
		case EKA_STRAFE_RIGHT: KeyMap.push_back(SCamKeyMap(EKA_STRAFE_RIGHT, map[i].KeyCode));
			break;
		case EKA_JUMP_UP: KeyMap.push_back(SCamKeyMap(EKA_JUMP_UP, map[i].KeyCode));
			break;
		default:
			break;
		}
	}
}


//! Sets whether vertical movement should be allowed.
void CSceneNodeAnimatorCameraFPS::setVerticalMovement(bool allow)
{
	NoVerticalMovement = !allow;
}


//! Sets whether the Y axis of the mouse should be inverted.
void CSceneNodeAnimatorCameraFPS::setInvertMouse(bool invert)
{
	if (invert)
		MouseYDirection = -1.0f;
	else
		MouseYDirection = 1.0f;
}


ISceneNodeAnimator* CSceneNodeAnimatorCameraFPS::createClone(ISceneNode* node, ISceneManager* newManager)
{
	CSceneNodeAnimatorCameraFPS * newAnimator =
		new CSceneNodeAnimatorCameraFPS(CursorControl,	RotateSpeed, MoveSpeed, JumpSpeed,
											0, 0, NoVerticalMovement);
	newAnimator->setKeyMap(KeyMap);
	return newAnimator;
}


void CSceneNodeAnimatorCameraFPS::setKeyMap(const core::array<SCamKeyMap>& keymap)
{
	KeyMap=keymap;
}


} // namespace scene
} // namespace irr

Debeli · Post by **Debeli** » Sun Apr 11, 2010 12:41 pm

Nice work Geo!!!I heard about that problem on the forum it s nice you fixed it.It seems like your project is going well cant wait to see it

soo nice work(Svaka cast)

etal2009 · Post by **etal2009** » Sun Apr 11, 2010 4:16 pm

Couldn't you have just normalized the vector?

I'm sure that's what you did in your code, but when you describe it beforehand, it sounds like you are just going to divide.

Geomaster · Post by **Geomaster** » Sun Apr 11, 2010 5:40 pm

Well, not sure which vector are you talking about. There are two vectors in play when diagonally moving, one for strafing and one for ahead at the same time. Both are normalized, but when you add them to the current camera vector, it's in fact moved for BothVectorsLength * sqrt(2). There is no diagonal vector; it's just the resulting vector when applying both ahead and strafing.

@Debeli: thanks! just not sure about what project, since i have a couple of them right now

etal2009 · Post by **etal2009** » Mon Apr 12, 2010 1:43 am

Not to say your way doesn't work, but i use another way with my custom camera. I add the front/back vector with the right/left vector, then normalize that vector and multiply by a movement_speed constant.