How Can You Make Underground Hallway BATs?

[metarvo]

To take a break from my power line BATs and gain some experience in other areas of BATting, I have decided to try BATting underground hallways.



As you can see, I'm experimenting with nightlighting as well.  The twist is that underground BATs can actually show indoor scenery, which isn't seen as much with most BATs.  Deadwoods' underground malls come to mind.  The plan is to BAT a canopy-like prop as well that will cover the opening.  The visible underground section of the lot that this particular BAT would go on should be 8m × 16m, and the stairway shown will lead above ground, meaning this would be a 1×2 lot.

However, I can't seem to figure out how to make this show up as an underground BAT without any of the exterior walls and the like showing.  I know I've seen some good underground BATs lately, such as the tunnels Dexter has been making for various transit networks.  Does anyone have any ideas on how I can make this go underground?

[mattb325]

Hi Metarvo.

To make something appear underground you need to have the LODS set correctly. Imagine that the LOD is just the frame of a picture; everything within this LOD space/frame is visible in game, everything outside the LOD space/frame is not visible. The analogy for an underground piece might be along the lines of placing that picture inside a shoe-box; you need your picture - and nothing else - to be visible when you lift the lid from all angles.

In your scene, if you 'unhide' everything, you will see that the three LODS wrap around your structure under the ground plane. GMAX has automatically placed them there when you did the preview render.

As this means the exterior of your underground creation fills the space of the LOD, it will always be visible, which of course will not do for the 'underground' illusion.

There are two main ways to correct this.

1) Highlight the three default LODS and move them so that they are above the ground plane. You will be able to shorten the height of each LOD in the parameters box. Then look at each zoom in the viewport (not the preview render): does the LOD box cover everything that needs to be seen and nothing (in terms of the interior scene - the exterior is fine) is sticking out? If so, the LODs are probably correct. You can also adjust the width of each LOD box in the parameters box. The beauty of this method is that you avoid the strange reverse shadows that occur with underground BATS. You may also need to BAT a perimeter ground texture to hide any visible exterior pieces.

2) Leave the LODs as set by GMAX and BAT a wide ground texture to cover the exterior visible parts of your model. This is a really common method to deal with the undergound parts: it works, but often causes more noticeably odd shadows.

Additionally, it looks like you will be making 'pieces' of hallways, so make sure that your LOD is 16m and that your BAT is longer than 16m to join them seamlessly.

Hope this makes sense, if not I can add images....

[metarvo]

Yes, I'm planning to make several hallway pieces, including entrances/exits, straight segments, corners, etc. that can be placed together seamlessly or placed separately to give the illusion that the hallway is going under a building or road.  As a result, part of the hallway that I've BATted is not included in the LODs.

Matt, I used the first method you described.  I moved the three LODs to 0 on the z-axis, resized them to 8 m × 32 m to cover the length of the hallway and the exterior staircase for a 2×1 lot.  Everything looked good in the renders shown during the export.  However, it was a different story when I opened up PIM-X and selected the model.  I saw this.



The model was upside-down.  When I made a building with the model and opened it with PIM-X's LE, I got this.



The building was invisible.  So, I clearly did something wrong with the BAT.  What would cause this?  I tried moving them slightly above 0, and the same thing happened.  Even z-mirroring and resizing the LODs had no effect.  I guess I could try the second method, but I would prefer to get the first one to work for the reasons you described.

[joelyboy911]

If things are appearing upside down, it may be a problem with your cameras (seperate from the underground LOD issue). Try opening a new scene, pressing one of the directions on the preview panel (to generate the cameras) and merge the relevant material from the existing scene into the new one. I've had experience with this in the past, where the cameras somehow get out of kilter, and I've ended up with something like this:



ie. A complete mess.

Hope this helps somewhat.

[mattb325]

The joys of GMAX 

Definitely merge everything (except the cameras and LODs 1,2 & 3) into a new scene. But the method should work.

Attached is an underground driveway prop that I made in the Mega Prop Pack 2.
The 1st pic just shows the whole structure underground, the second pic shows the LODs I dragged up and shortened so that they only covered the tops of the rails above ground, and didn't extend below ground, and the third is a side view which shows the extent of the batted ground in order to hide some of the visible walls (as well as the LODs)