Restrict user driven camera movement to a cubic area?

Questions
1

What’s the easiest way from my animation loop to restrict the movement of the camera, driven by the user’s keyboard and mouse, to an area defined by a cube?

In other words, in my code that converts keyboard and mouse changes to camera position changes, how can I easily detect when the camera is “touching” the boundary of an area defined by a cube (i.e. - fence them in)?.

So, there is no cube object in the world that I want to restrict movement inside, I just want to prevent the camera from exiting the boundaries of a predefined cubic area. Any code samples I can look at?

2

This might help Box3 – three.js docs (threejs.org).

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3

Even if there is no cube object in your scene, you could create one, make it BackSide and invisible, and use it for your purpose - that’s just one possibility, of course, and it would involve checking if the camera is outside the cube, translating the camera back (or inside the cube) on its direction (Z), getting its position and direction, use a raycaster to get the intersect point with the cube and then translating the camera forward to the intersect point aka the point you want it to stop.

I could share the “restrict movement outside” code I use, but it would probably need some adjustments for your case and there’s an easier way anyway. Since you’re talking about an imaginary cube and it’s a simple shape, the easiest way would be to just perform the movement in your key and pointer event listeners only if the camera position is within the space between the cube’s sides, i.e. in pseudo-code:

if (camera.position.x + cameramovementx >= cubeleftsidex &&
    camera.position.x + cameramovementx <= cuberightsidex &&
    camera.position.y + cameramovementy >= cubebottomsidey &&
    camera.position.y + cameramovementy <= cubetopsidey &&
    camera.position.z + cameramovementz >= cubebacksidez &&
    camera.position.z + cameramovementz >= cubefrontsidez)
{
// do your valid movement
};

That should be enough assuming you’re working with same local / world space values, but you can adapt it accordingly. For example, if the conditional is an option only after the movement happens, then you’d have to get the direction of the last camera movement and place it at the intersect point with the (now, not so imaginary) cube based on the inverse of the last camera movement (i.e. going backwards from the camera’s POV), aka more or less what I described in my first paragraph.

Or, you can follow @anidivr advice and use the .clampPoint(), .containsPoint() and .distanceToPoint() to test and restrict the point (i.e. camera position) within the said box.

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4

An alternative: Vector3.clamp(min, max)

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