Select Faces behind on 3D Solids
In AutoCAD 2007 and later 2008 it is possible to select the face behind. For example on a 3D box that would be the face on the backside. Procedure: Place the pickbox on the front face, next press down CTRL, while pressing down CTRL you hit the spacebar once and you see that the face on the back side is selected. Don't click on any faces before AutoCAD has selected the face. It's essential that you place the pickbox virtually on the face behind before you hit the spacebar, see image below. You can also select the other faces using the same procedure.
From AutoCAD 2007 a brilliant new 3D command arrived. It's called Presspull. If you have made a 3D box and want to make a hole through you can do that with PRESSPULL. First you create a rectangle with a polyline on top of 1 face on the 3D box. Next you activate PRESSPULL command and click inside the rectangle. Now you can make a hole by pulling the face on the rectangle inside the box. You can use this command for the existing faces of an object, or by imprinting additional faces on an object and pulling those inside or outside. If you pull it outside of the box, then you create a solid object pointing out from the 3D box. You can also use 3D POLYLINE instead of polyline. First align UCS so it's parallel with the side you are making a hole. Scroll down on this page to see tutorial "Creating a Wall with Polysolid".
3D Modeling in AutoCAD with Loft
With the LOFT command, you can create a new solid or surface by specifying a series of cross sections. The cross sections define the profile (shape) of the resulting solid or surface. It is recommend to use <cross sections only> or "Path", because it's easier to apply than "Guides". Use cross sections with arcs, polylines, lines or polygons. If you use closed polylines or circles as cross sections, then LOFT creates a solid in the space between the cross sections. You must specify at least two cross sections when you use the LOFT command. Use multiple arcs, splines, polylines or lines, if you like to create a open surface. Later, if you want to convert a 3D solid to a surface, then use the explode command. The LOFT command is great for 3D modeling of landscapes or other complex shapes. I used it for a ship hull.
First you create 3 splines, next you select them as cross-sections in order from A to C
Then you select Cross-sections only
Finally you select smooth fit and click ok
The open surface is created
Creating a Wall with Polysolid
A new 3D command in AutoCAD 2007 was POLYSOLID. Next I show how you create a wall, with a hole for a window.
Type Polysolid in the command line and press enter. Then type W to specify the width of the wall.
Next you type H to specify the height.
Next you specify a start point, then move the mouse to the right and type the lenght of the wall, followed by enter.
The wall is created.
Now you create a opening in the wall. First activate DYNAMIC UCS and OBJECT SNAP. Next you start the 3DPOLY command in the Tool palette.
Activate object snap midpoint and object snap tracking, then snap the middle of the wall's height (without clicking). To specify the start point, you move the mouse to the right and type the distance 1000, followed by enter.
Move the mouse upwards and type the half height of the opening, followed by enter.
Move the mouse to the right and type the lenght of the opening, followed by enter.
Next you move the mouse down and type the height of the opening.
Move the mouse to the left and type the lenght of the opening, followed by enter.
Next you type C to close the 3D polyline.
Rectangle is created.
Start the PRESSPULL command in the dashboard and click inside the rectangle.
Pull the mouse to the rear and type 500, followed by enter.
A long time missed feature in AutoCAD has finally arrived. It is the command SECTIONPLANE. For example to make a cross section view of a house. I will explain you the most easy way to do this.
Then chose <Orthographic> by typing O, followed by enter. Next you select left in the menu. You are done!
Final result, a cross section.