This is a mod for SCP: Containment Breach's Map Creator. It adds a 3D view to it, using the game's models to help you prevent room intersections.
That green sphere you see is used to place rooms. It follows the camera and tells you if you can place a room (or not).
Also, I found this video, made by Lyrahel (Games in Time):
To create a map with this, here are some instructions.
1. Select a room template from the list at the left of the window.
2. Change from 2D to 3D with the button at the bottom-right corner of the window.
3. Click on the 3D view to "focus" on the camera. The WASD keys will move the camera like in the game, and Left Shift will make the camera move faster.
4. Use the mouse wheel to adjust rendering distance.
5. Move the camera until the "ball" is green (if it's red then you can't place a room there), and near the start room's door.
6. Press Esc to "unfocus" the camera, and click on "Place 'roomName' " to place the room at the ball's coordinates.
7. Focus the camera, and click on the room you placed to select it (the ball will disappear, the room will have a green color, and you'll be able to rotate or remove the room)
8. Unfocus the camera, rotate the room as you like, toggle events, etc.
9. Create a map.
Extract this to your SCP:CB (at least version 0.7.4) directory, merge the folder, and run the edited executable in the Map Editor folder.
November 13th, 2013:
- A few bugfixes
November 12th, 2013:
- Rebuilt with newest map creator source code
- Fixed a bug with the room template list
- You can now choose between 2D- and 3D-mode
August 8th, 2013:
- Simplified crosshair (might fix a bug that crashed the editor)
- Added a shadow effect to the "ball"
- Fixed lighting when a room is selected
- Fixed a bug with the "Create new room" button
July 25th, 2013:
- Some optimization
- Fixed a bug that caused a Memory Access Violation
- When you select a room, it will turn green
- Added a "New room" button
- Fixed the camera's precision, selecting rooms should be easier
- Added an FPS meter
- Edited the "Place room" button, now it displays detailed information.
- Fixed exit1's (Gate B) terrain
- Added fog and rendering limits (change distance with the mouse wheel)
- Added a simple crosshair
July 24th, 2013:
- Initial Release.