Hi,
I was just wondering if anyone has any good idea how to solve this elegant?

I'm currently developing a 2D RPG engine and I'm trying to keep the rendering separate from the datamodel.
So I have like a Character class which has a position (map cordinates, 32px at the moment) and an id (and some other attributes that aren't needed for this question )
int x, y;
string id;

The "world" is rendered "constantly" and the character is rendered by a CharacterRender on the current cordinate.
The problem is that as soon the user presses LEFT I want to move the character left one map square (x = x -1) and I want the CharacterRender to create a pixel smooth animation to move the char from the current coordinate to the new coordinate

How would you solve it?

You could have PreviousPosition and DesiredPosition members, then a CurrentPosition(dt) method to interpolate the actual position based on a delta time value.

Assuming you poll input every frame, you would need to check desiredPosition != currentPosition before updating to the new desiredPosition.

The above is certainly one way of doing it. You could also do the following, which adds less variables to your model.

Store the pixel coordinates of the player as a float and increment them slowly in the game logic when the player pushes a key. Don't act on any new input until the float position has moved at least 32 pixels in the desired direction. Once it has completed the move, there might be some left over remainder on the pixel position, so just set the position to a multiple of 32 (p = floor(p / 32) * 32).

That's one way of doing it, there may be a better way though. The best way will be whatever suits what you've got already.

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Whatever the mind can conceive and believe, it can achieve

Thanks for the rapid response guys

I've been thinking about it and I think I want to constraint the movement so it's only possible to stop directly on a map tile. It's just the transfer between the map tiles that I want pixel positioning on.
(Is the "stop only directly on a tile" weird?)

I think it's possible to use IGTHORNs idea with some modification. But I have still not gotten that "This is the perfect solution" feeling

This is kind of a new experience for me, I'm usually a web/desktop application developer

Does anyone have any examples on how they have solved it in similar cases?

Welcome a-"board", Megamannen! (Sorry, I'm one who simply cannot resist taking advantage of an opportunity to lay out a pun. )

I don't have any code in front of me right this minute, but look into the concept of "linear interpolation". It's moving a value from point A to point B based on time -- it sounds exactly like what you're asking for.

I will try and work out a quick example -- but in the meantime, look into linear interpolation, and see if you can get the basic idea.

EDIT -- Sorry Megamannen, I forgot that my understanding of math is on par with that of a particularly retarded mayonnaise container. I can't find any of my old code that solves this issue, my books explain mathematics in Klingon, and I just don't have the skill to work it out on my own. I'm positive, though, that someone will come along very soon and get you on the right track. My apologies!

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What most people don't understand about "enlightenment" is that it is not an end-goal; but where you find yourself just before taking a new "first step."

Keeping your character restricted to tiles may be good depending on how your game plays - if positioning is important for blocking off enemies from paths or something strategic like that.

What other information are you storing for the characters? If you're storing some kind of elapsedTime value for animation purposes, you could extend that to do what I suggested. Maybe tell us a little more about what's going on and a better solution will present itself

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Whatever the mind can conceive and believe, it can achieve

Have three sets of coordinates:

For logic purposes:
(gridx, gridy) stores the integer grid location you are on.
(targetx, targety) stores the grid location you are moving to.

For graphics purposes
(drawx, drawy) stores the position of the sprite.

have an interpolator lambda that moves from one to the other.

drawx = gridx * (1 - lambda) + targetx * lambda
drawy = gridy * (1 - lambda) + targety * lambda

You can also use lambda to animate the walking motion, by selecting the appropriate frame to draw.
Once lambda is greater than or equal to 1, then the motion is completed, so let gridx = targetx, gridy=target y. and lambda=0

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I ain't pushing no moon buttons.

Restricted to tiles it is, you got me thinking about my battles and there the positioning is based on tiles. So why have it different outside of battles!? Thanks

I'll see if I can apply some of these ideas on my code, I'll be back

A good example of practicing the principle of KISS. (Keep It Simple, Sweetie -- because "stupid" is not allowed on this forum!*)

Looking forward to what you come up with. Stop by if you have any problems, as well!

*Exceptions to this rule include: rotInMilc calling himself stupid; and users in general calling rotInMilc stupid.

_________________
What most people don't understand about "enlightenment" is that it is not an end-goal; but where you find yourself just before taking a new "first step."