How to pan the camera when the player approaches the viewport edges in Castle Game Engine?

3D
1

Hi everyone,

I’m developing a top-down / RTS-style game in Castle Game Engine. I want the camera to automatically move (pan) when my player character approaches the edges of the viewport, similar to classic RTS games.

So far, I know how to move the player in the world, but I couldn’t find a built-in function or recommended approach to detect when the player is near the screen edges and move the camera smoothly.

Could you please advise on the best way to implement this? For example:

  • Should I convert the player’s world position to screen coordinates?
  • Or is there a frustum-based approach?
  • Any performance-friendly solution for multiple moving characters?

Thanks in advance for your guidance!

2

An example showing what you are trying to achieve would be great.

3

The most simple solution. You could simply decide how many tiles the player can move before the camera movement is required. It doesn’t have to be close to the edge. When player cross the threshold just change the camera position (X,Z) to the same as player.

Alternatively, you could have an invisible transform (an “observer”) that looks at the player, placed as a child of the camera. As the transform keep tracking the player, it changes its direction. You may decide than an angle of +/-30 degrees along X and Z axis, the camera should move.

In this topic LookAt / Target property or function for camera or any TCastleTransform - #3 by michalis @michalis gives a simple example of a “Look At” behaviour implementation. Just attach the behavior to the observer transform.

It is performance friendly.

During the camera movement you need to pause the “Look At” behaviour.

As an option, you could auto-calculate the min/max angle based on:

  • h = camera height,
  • d = maximum distance, or Tiles * tile_size, before you consider camera movement

by using simple trigonometry. If I’m not mistaken it’ll be ArcTan(d/h).

To animate the camera movement, you can also use behaviors which is easy, or just brute-force based on Update function.

4

I’ve done almost the same thing, but the movement isn’t smooth.

5

I want the camera to move when the player gets close to the edge, so that the player stays centered in the camera’s view.

6

Sorry for delayed answer. I’m very busy with some project.

To test it quickly I went the first route from my previous answer. Only “move to the right” is implemented here, and it’s recorded with standard Windows’ screen recorder.

In this example, inside Press function I just calculated the distance from Camera.Translation.X to the Box’s translation. When more than 500, I set (my own) variable “NeedCameraMove” to true.

Then in the Update I just do Camera1.Translation := Vector3(Camera1.Translation.X + Speed * SecondsPassed, …);

No math, no behaviors. I see no lag at all. If you experience a not-so-smooth movement, I guess it’s not related to the camera movement alone. Maybe it’d be better for your game if instead of moving all the way to the player’s position, you’d move just enough to keep the player visible. Less pixels to move inside the same timeframe.

Hope that helps.

1 Like
7

Thank you for replying.
I think I’m having trouble because I have camera zoom and the camera is in Camera1.Orthographic mode.
I’ll try to fix it.
Thanks.

—————–update —————
I see. I’m currently calculating the edge in update, but I should calculate it in press.
I’ll get to it in a few hours and fix it.