Help! The ‘union’ operation isn’t working.

[BLOCKQUOTE class=’ip-ubbcode-quote’][div class=’ip-ubbcode-quote-title’]quote:[/div][div class=’ip-ubbcode-quote-content’]Originally posted by Bazza:
I could build a city with 440 polys <!– s:) –><img src="{SMILIES_PATH}/icon_e_smile.gif" alt=":)" title="Smile" /><!– s:) –>, well nearly….
Bazza [/div][/BLOCKQUOTE]

He he, you’ll have to show me how. [img]’ alt=’Roll Eyes’ width=’15’ height=’15’]

I’ll send it to you but it has two walls, now and it works in the game, too.

<!– s:) –><img src="{SMILIES_PATH}/icon_e_smile.gif" alt="" title="Smile" /><!– s:) –>

Hi all,
OK, here goes.
I wanted a window in a wall so, I built a bottom wall section, a top wall section, and two side wall sections subtraction the dimensions of the window.
That worked perfectally! I now have a four sectioned wall with a hole in it. I then used the union tool to merge/join the four wall sections together as one wall.
That worked, also. Unfortunately, I now have one wall that has more faces and points in it then it did before. Removing the extra points and faces creates even more of a mess deforming the wall horribly. Applying the textures is now a nightmare with all the additional angled faces.
The instructions state that the union tool will join the sections together as one piece unlike the merge tool that leaves all the faces and points.
I then ran the optimize function but that didn’t help

What am I doing wrong and why doesn’t the union tool work per the instructions creating one wall with 6 faces and 8 points, not including the window/hole, which is another 4 faces and 8 points?

Thank you,


I made the test following your instructions.
It looks like the union operation is bugged.

Try this. I found it by mistake and it seemes to work well.

1. Drag a cube into the scene and scale it up by 10 in all directions.

2. Copy the cube and paste it into the scene. then scale it down to .9 in all directions.

3. Goto wire frame view and place the second cube inside the first one.

4. Flip the surfaces of the second cube and then merge the two together. This will give you a hollow object to work with.

5. Change the view back to smooth and create your window or door and subtract them from the object.

I hope this helps.

Here is a church i have been messn around with when i found this out.

The best way of course is to create the faces for windows and doors as you build the model.
But if you haven’t done this you can try this method…
1) Select the face where you want the window.(it needs to be four sided)
2) Click the Insert operation
3) Select the new face, scale it and move it to the window position.
4) Select it and do a negative extrude


[BLOCKQUOTE class=’ip-ubbcode-quote’][div class=’ip-ubbcode-quote-title’]quote:[/div][div class=’ip-ubbcode-quote-content’]Originally posted by DOM107:

I made the test following your instructions.
It looks like the union operation is bugged. [/div][/BLOCKQUOTE]

Thank you, Dom. I had thought I’d done it right.

@ Bazza, I used the term ‘window’ as a visual example. What I really want, in this case, is a square hole in a wall.
To clarify my need a little better, The wall is to stand 8’6′ tall by 10′ deep by 4′ thick with a 2′ square hole in it as a window. No glass nor frame for the hole/window, just the square hole.

EDIT: I have experimented with all the above suggestions including the Object Subtract Boolean opeation unfortunately, nothing leaves a ‘clean smooth’ wall that textures can be applied to without distortion.
Is there no way to ‘insert’ a hole in a wall leaving a ‘clean smooth’ surface on the wall without all the additional faces these create that interfere with the textures?

Thank you,

I have been struggling with making holes too..

Best method I have found in a flat solid is..

make a cube up to the bottom of the window height.
divide the top face twice.
reposition the edges to the window corner positions.
Select the faces that are not in line with the window and extrude to window height.
Extrude the same faces up to the eves.
Use the bridge tool to join the sections above the window.

Hope it may be of some use


My gosh, it works! Trimming up the faces is a bit tricky but I do have a clean surface to texture, now.

Thanks a million, Sly.

<!– s8-) –><img src="{SMILIES_PATH}/icon_cool.gif" alt="8-)" title="Cool" /><!– s8-) –>

Whilst the Boolean ops have thier uses there are better ways to create models like this…

Method one….
This works ok if you just want to apply a single texture to the whole object, say a brick texture.
This hasn’t been built to your wall dimensions.
1) Create a face with the Create Face plugin
2) Select the face and click the Insert operation
3) Select all the faces and use either the Double Sided operation or Plugin
4) Extrude the wall to the width you want
Select the inserted faces on both sides of the wall
Run the Bridge Operation.


Method Two….
Build the faces for the window AND textures into the model at the outset.
This is by far the best method and gives you more options when applying textures.
This is built to your wall dimansions, but didn’t know where you wanted the window opening.
1) Start with a cube scaled to X=2, Y=3, Z=0.25
2) Extrude the top face up by 2 (Pink, the size of the window)
And again by 3 ( the area above the window)
3) To get the opening into the middle of the wall I scaled to X=4
4) Select the wall edge and Extrude by 2 and then by 4
5) Select both the window faces on both sides of the wall and run the Bridge Operation

You now have a clean model with a hole in it.
It’s now much easier to apply different textures if you wish.


Taking it a step further…
1) By creating extra faces along the top and bottom, this gives you more options for texturing.
2) You can now add a cornice to the top faces.
The main brick texture to the center faces.
And some fancy stuff to the bottom faces.


It’s all down to a bit of forward planning and creating the initial cube object with the required faces.
I covered this stuff to some extent here….
<!– m –><a class="postlink" href=""> … 6410442141</a><!– m –>

And here….
<!– m –><a class="postlink" href=""> … 9010822931</a><!– m –>


Wonderful, Bazza. Thank you, too, so very much for all this extra information.
I’m still learning 3DC and am not aware of everything available to me yet. Or, at least, all of it’s capabilities.


A little quirk has arisen. The ‘holes’ don’t show up in the game. Not sure why but I gotta try something else, I guess…


Hi rick

try running the reduce points and faces operation followed by the Optimize geometry operation


Do you mean you are looking at a solid wall in your Game engine?
Thats not possible if you built the wall as I described as the hole doesn’t have any faces.
Which game engine are you using?


@ Bazza,
Yup! I thought it rather odd, also. Here it is in the game of Trainz 2004;


Here’s the model I exported from 3DC Pro;


I built the two walls as per Sly’s instructions then had to trim a few points to change the faces to apply my textures but all in all, here it is in a nutshell.

Not sure why the ‘windows’ aren’t showing in the game.
I’ve also added a bit more to the model but haven’t changed the wall/window area any. It’s the same model.

It’s hard to say without seeing the 3DC file.
Maybe you could zip it and post it, don’t need the textures.
Another test would be to just construct something like a wall object using the above method 2 and see if this imports into Trainz OK.
If it does then you have something wrong with the model you have.


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