TMainView.m

- (vec4_t)mapToSphere:(vec2_t)aWindowCoord // http://www.tommyhinks.com/docs/shoemake92_arcball.pdf
{
	// normalize window coordinates
	vec4_t viewport;
	glGetFloatv(GL_VIEWPORT, viewport.f);
	vec3_t p = { 2.0*aWindowCoord.x/viewport.z - 1.0, 2.0*aWindowCoord.y/viewport.w - 1.0, 0 };
	
	// Map to sphere
	float mag = p.x*p.x + p.y*p.y;
	if(mag > 1.0) {
		float scale = 1.0 / sqrtf(mag);
		p.x *= scale;
		p.y *= scale;
		p.z = 0.0;
	} else
		p.z = -sqrtf(1.0f - mag);
	vec4_t out = { .xyz = p, .andW = 1.0f };
	return out;
}

static vec4_t lastMouseLoc;
- (void)mouseDown:(NSEvent *)aEvent
{
	lastMouseLoc = [self mapToSphere:vec2_create(aEvent.locationInWindow.x, aEvent.locationInWindow.y)];
}

- (void)mouseDragged:(NSEvent *)aEvent
{
	vec4_t mouseLoc = [self mapToSphere:vec2_create(aEvent.locationInWindow.x, aEvent.locationInWindow.y)];
	
	TCamera *cam = [TScene globalScene].camera;

	quat_t rotation;
	rotation.vec = vec3_cross(lastMouseLoc.xyz, mouseLoc.xyz);
	rotation.scalar = vec3_dot(lastMouseLoc.xyz, mouseLoc.xyz);
	rotation = quat_normalize(rotation);
	
	cam.orientation = quat_multQuat(rotation, cam.orientation);
	cam.position = quat_rotatePoint(rotation, cam.position);

	[cam updateMatrix];
	lastMouseLoc = mouseLoc;
}