I am confused as to how applications handle the mouse input with Direct2D.
Consider the case:
Say I painted a ball on the window. If I move the cursor over the ball, it will change color.
Does this mean that the application have to poll the mouse and check if the cursor is over the ball pretty much every second of the application running time.
Doesn't that decrease performance when you have more items? Is there another way than what polling which in other words is a bunch of if-statements.
You need to perform the hit test when the mouse moves, or when the ball moves.
Efficient hit test / collision detection is a major concern in game development. If performance becomes an issue, collision detection is usually performed in two phases: A "broad phase" and a "narrow phase". One approach for the broad phase are quad trees (for two dimensions): The space (the window) is divided into "sections"; each ball and the mouse are assigned to a section according to their position. Only balls being in the same section as the mouse are candidates for the narrow phase. In the narrow phase, you just test the candidates that survived the broad phase.
Usually applications will listen for the WM_MOUSEMOVE event and update any affected objects in the event handler (or signal the objects of the change event in case it is an expensive operation). The render code shouldn't need to poll where the mouse cursor is.
Related
I am currently working on a new RPG game using Pygame (my aim here is really to learn how to use object oriented programming). I started a few days ago and developed a movement system where the player clicks a location and the character sprite goes to that location and stops when it get's there by checking if the sprite 'collides' with the mouse position.
I quickly found however that this greatly limited the world size (to the app window size).
I started having a look into making a movement system where the background would move with respect to the player, hence providing the illusion of movement.
I managed to achieve this by creating a variable keeping track of my background map position. The map is much bigger than the app window. And each time I want my player to move I offset the background by the speed of the player in the opposite direction.
My next problem now is that I can't get my character to stop moving... because the character sprite never actually reaches the last position clicked by the mouse, since it is the background that is moving, not the character sprite.
I was thinking of spending some time coding in a variable that would keep track of how many displacements it would take the character sprite to reach the mouse clicked position if it was to move. Since the background moves at the character sprite's speed it would take as many displacement of the background in the x and y directions to center the clicked position on the background to the character sprite at the center of the screen.
It would be something like that:
If MOUSEBUTTON clicked:
NM = set number of moves needed to reach the clicked position based on character sprite distance to click and character sprite speed.
If NM != 0:
Move background image
Else:
pass
This would mean that when my background has moved enough for the character sprite to now be just over the area of the background that was originally clicked by the player, the movement would stop since NM == 0.
I guess that my question is: Does that sound like a good idea or will it be a nightmare to handle the movement of other sprites and collisions ? And are there better tools in Pygame to achieve this movement system ?
I could also maybe use a clock and work out how many seconds the movements would take.
I guess that ultimately the whole challenge is dealing with a fixed reference point and make everything move around it, both with respect to this fixed reference, but also to their own. e.g. If two other sprites move toward one another, and the character of the player also "moves" then the movement of the other two sprites will have to depend both on the position of the other sprite and also on the offset of the background caused by the movement of the player's character.
An interesting topic which has been frying my brain for a few nights !
Thank you for your suggestions !
You actually asking for an opinion on game design. The way I look at it, nothing is impossible so go ahead and try your coding. Also it would be wise to look around at similar projects scattered around the net. You may be able to pick up a lot of tips without re inventing the wheel. Here is a good place to start.
scrolling mini map
I searched, but most posts are just telling me what I already have, so below is basically my code right now:
DIKeyboard->Acquire();
DIMouse->Acquire();
DIMouse->GetDeviceState(sizeof(DIMOUSESTATE), &mouseCurrState);
DIKeyboard->GetDeviceState(sizeof(keyboardState),(LPVOID)&keyboardState);
MousePos.x += mouseCurrState.lX;
MousePos.y += mouseCurrState.lY;
Any post telling me how to get absolute position just says to use those last two lines. But my program is windowed, and the mouse can start anywhere on the screen.
i.e. If my mouse happens to be in the centre of my screen, that becomes position 0,0. I basically just want the top left of my window (not my screen) to be my 0,0 mouse coordinates, but am having a hard time finding anything relevant.
Thanks for any help! :)
Following the discussion in the comments, you'll have to decide which method works best for you. Unfortunately, having never worked with DirectInput, I do not know the ins-and-outs of it.
However, Window Messages work best for RTS-style controls, where a cursor is drawn to screen. This is due to the fact that this respects user settings, such as mouse acceleration and mouse speed, whereas DirectInput only uses the driver settings (so not the control panel settings). The user will expect the mouse to feel the same, especially in windowed mode.
DirectInput works better for FPS-style controls, when there is no cursor drawn, as window messages give you only the cursor coordinates, and not offset values. This means that once you are at the edge of the screen, window messages will no longer allow you to detect the mouse being moved further (actually, I am not 100% sure on this, so if someone could verify, please feel free to comment).
For keyboard, I would definitely suggest window messages, because DirectInput offers no advantages, and WM input is easier to use, and quite powerful (the WM_KEYDOWN messages contains a lot of useful data), and it'll allow you (via TranslateMessage) to get good text input, adjusted to locale, etc.).
Solving your problem with DirectInput:
You could probably use GetCursorPos followed by ScreenToClient to initialise your MousePos structure. I'm guessing you'll need to redo this every time you lose mouse input and reacquire it.
Hybrid solution (for RTS like controls):
It might be possible to use a hybrid solution for the mouse if you desire RTS-like controls. If this is the case, I suggest, though I have not tested this, to use WM for the movement of the mouse, which avoids the need for workaround mentioned above, and only use DirectInput to detect additional mouse buttons.
Now one thing I think you should do in such a hybrid approach is not directly use the button when you detect it via DirectInput, but rather post a custom application message to your own message queue (using PostMessage and WM_APP) with the relevant information. I suggest this because using WM you do not get the real-time state of the mouse & keyboard, but rather the state at the time of the message. Posting a message that the button was pressed allows you to handle the extra buttons in the same state-dependent manner (I don't know how noticeable this 'lag' effect is). It also makes the entire input handling very uniform, as every bit of input with this enters as a window message.
Reading this article "Taking Advantage of High-Definition Mouse Movement" - http://msdn.microsoft.com/en-us/library/windows/desktop/ee418864(v=vs.100).aspx, I surmise that one should use raw input for more precise readings from input devices.
The article states that WM_MOUSEMOVE's primary disadvantage is that it is limited to the screen resolution.
Upon close inspection of the RAWMOUSE structure I see that lLastX and lLastY are long values and you get the delta via them.
To me it looks like WM_MOUSEMOVE and WM_INPUT is the same except with WM_INPUT you do not get acceleration (pointer ballistics) applied.
Are both WM_MOUSEMOVE and WM_INPUT limited to the screen resolution?
If so, what is the benefit of using WM_INPUT?
RAWMOUSE gives you logical coordinates for the mouse based on the mouse's native resolution.
That is, you see the actual movement of the mouse.
Windows will use the mouse speed and acceleration (ballistics) settings to update the cursor position. Because of course the two are not linked - the apparent movement of the mouse must be interpreted to generate a cursor movement else how can more than one mouse be supported?
If you wish to control a pointer, as far as I can tell there is no reason to duplicate the Windows mouse ballistics calculations. Just let windows do it. Therefore for controlling the pointer, you should just use WM_MOUSEMOVE. That is, unless you wish to disable the mouse acceleration settings in your application.
However, if you want to control the player's POV (point of view), or use the mouse to control an in-game object such as a spaceship flight yoke, then the RAWMOUSE data gives you the best possible access to the movement of the mouse, and you can implement your own algorithm to convert that into flight yoke/POV movement.
The main benefit and reason to use it is that that with rawInput you can use two mouses or more. Presently I write small game prototype which is designed to be played by two players with two mouses/mices - It is more complicated but It works and it is not bad because I do nod need to link external libs.
Is there any way to change the touch priority for cocos2d iOS sprites? What I have are multiple cards on the screen and they are arrayed in an arc, just like it would when you hold them in your hands. So in this setup, they overlap, and I need to recognize on which card the touch was made. I could measure the coordinates of each vertex of cards and determine the visible area of a card and then check if the touch was made inside that area (couldn't I?) but I thought there would be an easier way to deal with this, say changing the touch priority? Which means that the card closest to the screen would have the highest priority and it'll keep decreasing along the way into the background, so that even if the touch was made on 2 sprites at once (the above and below one), it would be registered only on the sprite with higher priority.
Reading on the internet only revealed ways to change the priority for a sprite and layer so that it defines whether the touch was made on the layer or the sprite, but that's not what I want.
As far as I know, by default you get exactly that behavior, the sprites closer (on the z ax) to you have priority. However, I think they pass down the event to the ones behind them as well. So, what i think you need to do is to eat the event when it gets to any of your sprites. To do that, just return NO when overwriting the "touchBegin" method. Hope it helps.
I'm currently writing a c++ console application that grabs the mouse position at regular intervals and sends it to another visual application where it is used to drive some 3d graphics in real time. The visual app is closed source and cannot be altered outside it's limited plug-in functionality.
Currently I'm using the GetCursorPos() function which is easy and fast enough, but I'm running into the issue that all of the data is clipped based on the current screen resolution of 1920x1600 so that all x values are between 0 and 1920 and all y values are between 0 and 1600 no matter how far the mouse is physically moved.
I need to get the mouse position before it's clipped at the edge of the screen, or possibly the deltas which I could use to calculate the current position.
I've seen some references to the windows MouseMove event but I would really not want to implement a window to make it work or especially have it as the active to receive those events.
I'm working in a windows environment and a language change is not feasible.
I might be wrong, but in Win32 land you don't get mouse move messages when the mouse is at the edge of the screen because, well, the mouse isn't moving. The usual way to get an infinite mouse area is to do the following:
Hide the mouse, get exclusive access and record position
Centre mouse to window
When mouse moves, get delta from centre of screen to current position
Centre mouse to window again
The next mouse move should have a delta of (0,0), so ignore it
Go to 3 until end of mouse move operation
Reset position, show the mouse and release exclusive access
If you didn't hide the mouse, then you'd see the mouse moving a small distance and then snapping back to the centre position, which looks nasty.
This method does require a message pump for the mouse move messages so the console application idea probably won't work with this. Can you create a full screen invisible window for grabbing the mouse?
Just get the position, and move it to the center and return the delta yourself
This is how FPS games do it
I don't have any direct experience with raw input, which is probably what you need to tap into. According to MSDN, you have to register the device, then setup your winproc to accept the WM_INPUT messages and then do your calculations based on the raw data.
Here's another relevant link.