void XICamera.Update(GameTime game_time)
{
if (mListener_WorldRegenerated.GetMaxOne() != null)
{
InitFromWorld();
}
XTouch.MultiDragData multi_drag_msg = mListener_MultiDrag.GetMaxOne();
if (multi_drag_msg != null)
{
if (multi_drag_msg.mFrameCount == 0)
{
mMultiDragPrev = multi_drag_msg;
}
// figure out zoom. damp so that human powered drag zoom is not jittery.
// it's not that there is anything wrong with the measurement or the calculation, it's
// that people don't seem to keep their fingers at constant separation when they mean to.
const float k_zoom_damping = 0.8f;
float ideal_zoom_ratio = (float)(mMultiDragPrev.mMaxScreenSeparation / multi_drag_msg.mMaxScreenSeparation);
float zoom_ratio = (mDampedMaxScreenSeparation > -1f) ?
(k_zoom_damping * mDampedMaxScreenSeparation + (1f - k_zoom_damping) * ideal_zoom_ratio) :
ideal_zoom_ratio;
mDampedMaxScreenSeparation = zoom_ratio;
// place new world view so that the zoom point in world space is at the same place on the screen.
Vector2 size_0 = mWorldView.GetSize();
Vector2 size_1 = zoom_ratio * size_0;
Vector2 avg_world_pos = CalcWorldPos(multi_drag_msg.mAvgScreenPos);
float pos_x_fraction = multi_drag_msg.mAvgScreenPos.X / mScreenDim.x;
float pos_y_fraction = multi_drag_msg.mAvgScreenPos.Y / mScreenDim.y;
float dx_world = pos_x_fraction * size_1.X;
float dy_world = pos_y_fraction * size_1.Y;
Vector2 p0 = new Vector2(avg_world_pos.X - dx_world, avg_world_pos.Y - dy_world);
Vector2 p1 = p0 + size_1;
xAABB2 world_view = new xAABB2(p0, p1);
// figure out translation
// this calculation assumes fullscreen, viewport not taken into consideration
Vector2 pixel_move = multi_drag_msg.mAvgScreenPos - mMultiDragPrev.mAvgScreenPos;
Vector2 screen_fraction = new Vector2(pixel_move.X / mScreenDim.x, pixel_move.Y / mScreenDim.y);
Vector2 world_view_size = world_view.GetSize();
Vector2 world_move = new Vector2(screen_fraction.X * world_view_size.X, screen_fraction.Y * world_view_size.Y);
world_view.Translate(-world_move);
mMultiDragPrev = multi_drag_msg;
// clamp and calc projection matrix
mWorldView = ClampWorldView(world_view);
CalcProjectionMatrix();
}
}
private void InitFromWorld()
{
mWorldSize = XWorld.Instance().GetMapSize();
// initial view of map
xAABB2 world_view = new xAABB2(new Vector2(0, 0), new Vector2(mWorldSize.x, mWorldSize.y));
mWorldView = ClampWorldView(world_view);
// view matrix is unchanging
Vector3 pos = new Vector3(0, 0, 1f);
Vector3 target = pos - 2f * Vector3.UnitZ;
mViewMatrix = Matrix.CreateLookAt(pos, target, Vector3.UnitY);
CalcProjectionMatrix();
mMultiDragPrev = new XTouch.MultiDragData(Vector2.Zero, 1f, 0);
mDampedMaxScreenSeparation = -1f;
}