有背景或摄像头和QUOT;滚动＆QUOT;基于字符内的位置 [英] Having the Background or Camera "Scroll" based on charcter position

问题描述

我工作的一个RPG游戏，有一个自顶向下视图。我想加载图片到被什么字符走在后台，但到目前为止，我还没有想出如何正确有背景重绘，这样它的滚动。大部分时间我发现的例子是自动滚动。

I'm working on an RPG game that has a Top-Down view. I want to load a picture into the background which is what the character is walking on, but so far I haven't figured out how to correctly have the background redraw so that it's "scrolling". Most of the examples I find are auto scrolling.

我希望相机仍然集中在，直到你的背景图像达到其边界的字符，则字符将移至不重画在其他位置的图像。

I want the camera to remained centered at the character until you the background image reaches its boundaries, then the character will move without the image re-drawing in another position.

推荐答案

你的问题有点不清楚，但我觉得我得到它的要点。让我们来看看你的要求。

Your question is a bit unclear, but I think I get the gist of it. Let's look at your requirements.

1. 您有开销相机的寻找直接向下到一个二维平面上。我们可以重新present此作为一个简单的{X，Y}坐标对，对应于在飞机上的点的摄像机正在
2. 摄像机可以跟踪某个对象的游戏世界中的运动，可能是球员，但更普遍的东西。
3. 相机必须保持游戏世界的有限范围内。

这是很简单的实现。从广义上讲，地方你的更新（）方法中，你需要进行的步骤，履行各自的这些要求：

Which is simple enough to implement. In broad terms, somewhere inside your Update() method you need to carry out steps to fulfill each of those requirements:

if (cameraTarget != null)
{
    camera.Position = cameraTarget.Position;
    ClampCameraToWorldBounds();
}

在换句话说，如果我们有一个目标对象，锁定了我们的立场，以自己的立场;但要确保我们不会去出界。

In other words: if we have a target object, lock our position to its position; but make sure that we don't go out of bounds.

ClampCameraToBounds（）也容易实现。假设你有一些对象，全球，其中包含一个界属性，再presents在全球范围内像素：

ClampCameraToBounds() is also simple to implement. Assuming that you have some object, world, which contains a Bounds property that represents the world's extent in pixels:

private void ClampCameraToWorldBounds()
{
    var screenWidth = graphicsDevice.PresentationParameters.BackBufferWidth;
    var screenHeight = graphicsDevice.PresentationParameters.BackBufferHeight;

    var minimumX = (screenWidth / 2);
    var minimumY = (screnHeight / 2);

    var maximumX = world.Bounds.Width - (screenWidth / 2);
    var maximumY = world.Bounds.Height - (screenHeight / 2);
    var maximumPos = new Vector2(maximumX, maximumY);

    camera.Position = Vector2.Clamp(camera.Position, minimumPos, maximumPos);
}

这可以确保相机从来没有超过半个屏幕更接近世界的边缘。为什么半个屏幕？因为我们已经定义了相机的{X，Y}为点的相机在看的，这意味着它应始终在屏幕上居中。

This makes sure that the camera is never closer than half of a screen to the edge of the world. Why half a screen? Because we've defined the camera's {x, y} as the point that the camera is looking at, which means that it should always be centered on the screen.

这应该给你，你在你的问题中指定的行为，一个摄像头。从这里，这是实现你的地形渲染的只是一个问题，这样你的背景绘制相对于{X，Y}坐标相机对象指定。

This should give you a camera with the behavior that you specified in your question. From here, it's just a matter of implementing your terrain renderer such that your background is drawn relative to the {x, y} coordinate specified by the camera object.

由于在游戏世界中的物体的位置坐标，我们可以把这个位置到摄像机空间：

Given an object's position in game-world coordinates, we can translate that position into camera space:

var worldPosition = new Vector2(x, y);
var cameraSpace = camera.Position - world.Postion;

然后再从摄像机空间到屏幕空间：

And then from camera space into screen space:

var screenSpaceX = (screenWidth / 2) - cameraSpace.X;
var screenSpaceY = (screenHeight / 2) - cameraSpace.Y;

您可以使用对象的屏幕空间的坐标来呈现它。

You can then use an object's screen space coordinates to render it.

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