Holes in Objects

[Dennis]

Stiglr is right on track here --- Andy also posted a visual tutorial on making a round hole in a rectangle:

http://www.ac3d.org/forum/viewtopic.php?t=1012

[jleslie]

Originally Posted by Dennis

Stiglr is right on track here --- Andy also posted a visual tutorial on making a round hole in a rectangle:

http://www.ac3d.org/forum/viewtopic.php?t=1012

is this available? how can I drill a bolt hole in a cube? I don't want the hole to go all the way through the cube. and I also want a hole all the way through the cube.

[jleslie]

this is driving me crazy. how can I drill a drainage hole through the all the surfaces? the cylinder represents where I want the hole to go. I made the fins rack with the polygon tool and then extruded, and the cylinder is the circle polygon and then extruded. I set the tools to object mode, then I click on the rack, then I add the cylinder, and then I do object->boolean-> subtract, but its all messed up. Whats the right way to do this?

[Andy]

From looking at your result in AC3D, it appears that some of your surfaces are facing the wrong way.

I can tell this by setting all surfaces to 1S (single -sided) and looking around the object. If surfaces 'disappear' then they are the wrong way around.

For booleans to have any chance of working, you need to get all normals facing outwards on all objects used.

To fix the original, select one surface (that you know is facing correctly), and use Surface->Unify-normals.

[jleslie]

Originally Posted by Andy

From looking at your result in AC3D, it appears that some of your surfaces are facing the wrong way.

I can tell this by setting all surfaces to 1S (single -sided) and looking around the object. If surfaces 'disappear' then they are the wrong way around.

For booleans to have any chance of working, you need to get all normals facing outwards on all objects used.

To fix the original, select one surface (that you know is facing correctly), and use Surface->Unify-normals.

THANK YOU!!!! so the normals make a difference! I had no idea. Let me play with that and see;If I can get better results.

[jleslie]

Andy,

It worked! thanks again. I was able to make the exact drill hole I wanted. I am confused about the exact layout I needed for the surface face though. as shown in image1 in the yellow circle. I had to have the surfaces of the cylinder from 9:51 to 5:30 facing outward, and from 5:31 to 9:50 facing in to get it to work. I did it by trial and error, but is there a more logical way to decide?

[Andy]

All surfaces should face outwards - that way, the boolean operations know what's 'inside' or 'outside'.

You should probably check the result more carefully. Switch it to single sided and you may see holes where the cylinder surfaces that were wrong touched the main object.

You might want to check the objects for leaky surfaces before you do the boolean too. Any holes, even if they are hard to see, can cause problems with the boolean ops.