实施“抢夺"3D 场景中的相机平移工具

问题描述

在我的场景中，我想抓取"地形，然后在移动光标时让相机平移(其高度、视图矢量、视野等都保持不变).

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.

所以最初的抓取"点将是世界空间中的工作点，我希望该点在我拖动时保持在光标下.

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.

我当前的解决方案是获取前一个和当前屏幕点，取消投影它们，从另一个中减去一个，然后用该向量转换我的相机.这与我想要的很接近，但光标并没有完全停留在初始场景位置上，如果您从地形边缘附近开始，这可能会出现问题.

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));
}

感谢任何想法.

推荐答案

多睡一会儿:

• 获取相交点在世界空间和在模型空间(相对于模型的原点)的初始位置

• 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()

• 创建一条从相机穿过鼠标位置的光线:{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)

• 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 (注意dividebyzeroexception)

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

-> 在 NewPos_worldspace 中重新注入 x = ray.start + x * ray.dir

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

• 从中减去 initialpos_modelspace 以重新居中"模型

不过，最后一点似乎很可疑.

The last bit seems suspect, though.

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