实现一个＆QUOT;抢＆QUOT;在3D场景摄像机平移工具 [英] Implementing a "grab" camera panning tool in a 3D scene

问题描述

在我的场景我有地形，我想抢，然后让相机锅（其高度，查看载体，视野等方面都保持不变），因为我移动光标。

In my scene I have terrain that I want to "grab" and then have the camera pan (with its height, view vector, field of view, etc. all remaining the same) as I move the cursor.

因此​​，最初的抢点将在世界空间的工作点，我想这一点仍然光标下为我拖累。

So the initial "grab" point will be the working point in world space, and I'd like that point to remain under the cursor as I drag.

我目前的解决方案是采取previous和当前屏幕分，unproject他们，减去从另一个，并翻译我的相机与载体。这是接近我想要的，但光标不完全停留在初始场景的位置，如果你开始地形的边缘附近，可能会产生问题。

My current solution is to take the previous and current screen points, unproject them, subtract one from the other, and translate my camera with that vector. This is close to what I want, but the cursor doesn't stay exactly over the initial scene position, which can be problematic if you start near the edge of the terrain.

// Calculate scene points
MthPoint3D current_scene_point =
   camera->screenToScene(current_point.x, current_point.y);
MthPoint3D previous_scene_point =
   camera->screenToScene(previous_point.x, previous_point.y);

// Make sure the cursor didn't go off the terrain
if (current_scene_point.x != MAX_FLOAT &&
    previous_scene_point.x != MAX_FLOAT)
{
   // Move the camera to match the distance
   // covered by the cursor in the scene
   camera->translate(
      MthVector3D(
         previous_scene_point.x - current_scene_point.x,
         previous_scene_point.y - current_scene_point.y,
         0.0));
}

任何想法是AP preciated。

Any ideas are appreciated.

推荐答案

对于一些更多的睡眠：

• 让您的相交点的初始位置，在世界空间中的和的在模型空间（相对于模型的原点）

• Get the initial position of your intersected point, in world space and in model space ( relative to the model's origin)

即使用screenToScene（）

i.e use screenToScene()

• 创建一个线，它从相机通过鼠标位置：{ray.start，ray.dir}

ray.start是camera.pos，ray.dir是（screenToScene（） - camera.pos）

ray.start is camera.pos, ray.dir is (screenToScene() - camera.pos)

• 在解决NewPos = ray.start + X * ray.dir知道NewPos.y = initialpos_worldspace.y;

- > ray.start.y + X * ray.dir.y = initialpos_worldspace.y

-> ray.start.y + x*ray.dir.y = initialpos_worldspace.y

- > X =（initialpos_worldspace.y - ray.start.y）/rad.dir.y（小心dividebyzeroexception的）

-> x = ( initialpos_worldspace.y - ray.start.y)/rad.dir.y (beware of dividebyzeroexception)

- >回注的X NewPos_worldspace = ray.start + X * ray.dir

-> reinject x in NewPos_worldspace = ray.start + x * ray.dir

• substract initialpos_modelspace从重新中心的模式

最后一点似乎犯罪嫌疑人，但。

The last bit seems suspect, though.

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