Define a new exterior project or add a new exterior Scene to your project " New project" >  "Exterior".

Choose a rectangular, or – in this case - polygonal scene shape as required.

If desired you can  "Edit nominal values"  as of EN 12464-2 (optional).

    

Selection of exterior scenes: polygonal or rectangular. 

Edit nominal values as of EN 12464-2 (optional)  

After that dialog, you will be in 2D edit mode where you can define the room shape and the length of each wall.

You can end this 2D edit mode with a  double click  or the " ENTER"  key.

 2D editing mode.

Setting the extrusion direction.

If you want to add or remove corner points, select the scene and find the " Insert vertex"  or " Delete vertex"   command in the menu " Start".

Click on the corner point to move it, or to delete it, click on the blue line between two corner points to add a new point.

Delete or Insert vertex.

Clicking on the corner point to move it.

Note:  During the drawing command, you can change the snap grids or use zoom functionalities. 

The backspace key will remove the last corner point.

Uncalculated 3D-view of this scene.

3D objects in ReluxDesktop.

Note: There are various kinds of 3D objects available to design the exterior scene more detailed. Therefore you can select: "Insert" > "3D Object".