Unproject鼠标让3D世界坐标Libgdx [英] Unproject mouse to get 3D world coordinates Libgdx

问题描述

我的提问：我​​如何得到一个三维模型，以鼠标光标移动保持模型的y位置为0（使用Libgdx）

My Question: How do i get a 3D model to move with the mouse cursor keeping the y location of the model at 0. (Using Libgdx)

什么我已经尝试过： 我试图让我的三维模型跟随我的光标。

What i have tried: I'm trying to get my 3D models to follow my cursor.

目前，我只是做了模型运动与x和我的鼠标与添加的因素，如乘数和摄像头位置y坐标。这不太好，因为它不遵循光标，如果我旋转摄像头，则该模型没有在正确的方向前进。

At the moment i have simply made the models move with the x and y coordinates of my mouse with adding factors like a multiplier and camera location. This is not very good because it doesn't follow the cursor and if i rotate the camera then the model doesn't move in the correct direction.

这是用于移动模型codeI：

This is the code i used for moving the model :

instances.get（modelIndex）.transform.setToTranslation（（（Gdx.input.getX（） - 650）/ 10）+ cam.position.x，0，（（Gdx.input。 getY（）以 - 400）/ 10）+ cam.position.z）;

下面有一个链接到这个问题的图像（绿色圆圈就是鼠标）。

Here's a link to an image of the problem (The green circle is where the mouse is).

我知道，我要对此错误的，我应该使用unproject方法。我曾尝试使用unproject方法确实有一点成功，该模型只是坚持相机的近窗格中。我想留在0我的对象在y轴上，所以我用这个

I know that I'm going about this wrong and that I should be using the unproject method. I have tried to use the unproject method and did have little success, the model was just stuck to the near pane of the camera. I want my object to stay at 0 on the y axes so i used this

cam.unproject(mousePos);
instances.get(modelIndex).transform.setToTranslation(mousePos.x, 0, mousePos.z);

这则导致模型中的移动很慢（不使用鼠标），在正确的方向。此外，当我旋转或移动摄像头的模式将在距离或力挺摄像头。

This then resulted in the model moving quite slowly(not with the mouse), in the right direction. Also when I rotated or moved the camera the model would be set somewhere in the distance or even behind the camera.

推荐答案

您不能简单地使用 camera.unproject ，因为一个二维的坐标可以重新present多坐标在三维空间。相反，你可以使用 camera.getPickRay 获得雷，这是由原点（相机的位置定义近平面）以及一个方向到三维空间。所以，你会得到的线在三维空间的重新presents二维坐标：

You cannot simply use camera.unproject, because a single 2D coordinate can represent multiple coordinates in 3D space. Instead you can use camera.getPickRay to get the Ray, which is defined by the origin (the location on the camera's near plane) along with a direction into 3D space. So, you'll get the line in 3D space that represents the 2D coordinate:

Ray ray = cam.getPickRay(screenX, screenY);

现在你想在这一行（线），其中Y = 0点（距离产地）：

Now you want the point (distance from origin) on that line (ray) where y=0:

ray.origin.y + ray.direction.y * distance = 0 <=>
ray.direction.y * distance = -ray.origin.y <=>
distance = -ray.origin.y / ray.direction.y

致使：

float distance = -ray.origin.y / ray.direction.y;

现在让在这个距离上的光线的位置：

Now to get the position on the ray at that distance:

Vector3 tmpVector = new Vector3();
tmpVector.set(ray.direction).scl(distance).add(ray.origin);

要设置模型实例转换到该值可以使用：

To set the model instance translation to that value you can use:

instance.transform.setTranslation(tmpVector);

下面实例指的是你的 instances.get（modelIndex）。

我会鼓励你使用InputProcessor（见<一href="http://$c$c.google.com/p/libgdx/wiki/InputEvent">http://$c$c.google.com/p/libgdx/wiki/InputEvent),所以把它放在一起：

I would encourage you to use InputProcessor (see http://code.google.com/p/libgdx/wiki/InputEvent), so to put it all together:

Vector3 tmpVector = new Vector3();
@Override
public boolean touchDragged (int screenX, int screenY, int pointer) {
    Ray ray = cam.getPickRay(screenX, screenY);
    final float distance = -ray.origin.y / ray.direction.y;
    tmpVector.set(ray.direction).scl(distance).add(ray.origin);
    instance.transform.setTranslation(tmpVector);
    return true;
}

请注意，您可能需要重写接地并返回真为 touchDragged 被调用。

Note that you might need to override touchdown and return true for touchDragged to be called.

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