Blended Box Mapping
By Neil Blevins
Created On: May 15th 2006
Updated On: Nov 29th 2011

Go here to read this tutorial in Russian.

Go here if you'd like a way to make a Blended Box Map in mentalray for Maya. Go here if you'd like a way to make a Blended Box Map in for Maya using no external plugins. And here's a script that helps to automate the process.

Say I want to apply some dirt to a bunch of objects in my scene. While I could use procedural noise, I'd prefer to use bitmaps since that will make the dirt will look a little more organic. But I don't want to spend a long time setting up good UVs for all of the objects, because that will take awhile. This is a tutorial that discusses a quick and easy way to apply a noisy bitmap to a bunch of objects without the need to unwrap their uvs.

Regular Box Mapping

So lets start with a reasonably random and noisy bitmap like the following...



And you have a somewhat irregular object like this...



And you'd like to quickly apply this pattern to your object.

As already mentioned, one way is to unwrap your object's uvs. This will let you apply a very specific patterns to your object without stretching or seams, but it can take awhile to set up, especially if you have lots of objects in your scene, and is overkill for a lot of situations.

A quicker way would be to use box mapping on the object. Box mapping is a mapping type that projects your texture from the six sides of a box at your object. So apply a UVW Mapping modifier to your object, set the mapping type as box, and render...



Well, that sort of worked, except there's a bunch of bad seams. Why is that? So if you use box mapping on an object that has rounded corners, faces of your mesh that point towards one of the 6 sides of the box map work fine. But if a face is near a 45 degree angle to the sides of the box, you get a seam where different sides of the box apply mapping to each face. For example, say a face is 44.5 degrees away from the front of the box map, it will receive mapping from the front of the box. Now say the next face is 45.5 degrees away from the front of the box map, it will receive mapping from the side of the box. So between those two faces you get a seam.

Lets look at the same problem on a sphere.



Instead of a noisy map, this is a custom uv map applied using regular box mapping. Notice the seams right at the edges where faces are near a 45 degree angle to any given side of the box map.

If only there was some way to blend these seams.

RIP InstantUV

Well, back in the earlier days of max (Max 4) there was a plugin called InstantUV that did this sort of thing. But the developer decided to stop selling it, and it never got recompiled for more modern versions of max.

Blended Box Mapping Using UVWMapping

So if there's no plugin to do this sort of thing anymore, we're just going to have to construct our own box map with blended edges. The trick for manually making a blended box map is to apply 3 planar UVW Mapping modifiers using 3 different map channels to your objects, and then blend their edges using falloff maps. This method is kind of ugly, but the results are think are worth the mess.

Take a peak at the map tree...



And a look at the 3 uvw mapping modifiers...



Also note, in the output section of the 2 falloff maps are curve controls, and modifying these curve controls achieve a sharper or blurrier transition on the edges.

Here's a max 8 example file that gives an example of how this works.

And here's the results...



Notice the blending between the edges. Now this isn't ideal for something with a regular pattern like this uv map, but lets go back to our original example of the noisy looking map...



The seam is basically gone (if you look real close you can sorta see it, but 3d is all about illusion, if the viewer can't see it on first read then it might as well not be there). And remember, the noisier the map is, or the more box-like your object is, the better this will work.

Now reproducing a Blended Box Map by hand on a new piece of geometry can be a bit complicated, so I've automated the process and wrote a maxscript that will make the map-tree and UVWMapping gizmos for you. Please visit my Soulburn Scripts for 3dsMax page and get the latest SoulCollection. Install the scripts, and run the script called blendedBoxMapMaker. Here's an interface snapshot...



To run the script, select the objects you want to apply the 3 UVW Mapping Modifiers to, in the script interface window choose "UVW Mapping Method", choose the bitmap you want to use for your blended box map, and hit "do".

So lets say you have an air vent like you see below, which is made up of 20 separate objects, and I want to apply some noisy dirt to all the pieces. So lets use a Blended Box Map.



I select all the objects, run my script like I describe above, and voila, it creates the three necessary mapping modifiers...



It adds the map tree to the material editor...



And I'll place the map tree into the diffuse slot of a material assigned to the air vent so you can see the result rendered...



Now artistically, this doesn't look fantastic, but if you replace this bitmap with something a little better, you can get some great results...



You can use this map tree anywhere in your material, one technique I use a lot is to use the map tree in the mix map of a blend material to blend between a metal material and a dirt material...



So there, I've added some dirt from a bitmap to 20 objects in just a few button clicks, no tweaking procedural parameters, no unwrapping.

The "UVW Mapping Method" does have a few downsides...

• The mapping modifiers are attached to each individual object. So if you move one of your objects, the mapping modifiers will become misaligned.
  
• Your objects need to have their transforms reset in order to get the falloff maps to align properly with the world (this is done using the Reset XForm utility in max). This is especially bad if you want to keep your original transforms on the objects.
• Adding a new object to your mapping requires copying and pasting three separate mapping modifiers, and in the process of pasting them, again, they may become misaligned.

Here's an example of mis-alignment. I decide to move one of my bolts on the air vent AFTER I have set up a Blended Box Map using the "UVW Mapping Method". Since the UVW Mapping Gizmos are attached to my objects, moving the bolt moves just one of the gizmos. Now I have multiple gizmos in multiple locations in 3d space, instead of them all being nicely aligned.



So the "UVW Mapping Method" has a number of pretty major downsides. Thankfully, there is now a better method.

Blended Box Mapping Using Projections By Script

First off, you will need the free plugin CameraMapGemini v0.16 or higher by Markus Boos (http://www.projectgemini.net/CameraMapGemini/). Install the plugin, and run max. Now go back to the blendedBoxMapMaker script and change the mode to "CameraMapGemini Method".



Run the script, select the air vent, and notice a few changes.

First, instead of applying 3 UVWMapping modifiers, it applies a single CameraMapGemini modifier to your object, and creates 3 projection cameras.



These cameras will project your texture, much like how the UVW Mapping modifiers did, except the cameras are not attached to each separate object. Decoupling the projection position from the object position means no more misaligned projections. And if you need the projections to move with the objects, just parent the camera projection group (a point object seen in the above image in light green) with the parent of your geometry hierarchy. Now whenever you move your whole air vent, the projection cameras will move with it, and so the projection stays attached to your objects.

Now check out the CameraMapGemini modifier assigned to your objects...



Notice the modifier references your three projection cameras. But since there's only a single modifier, adding new objects to your air vent is easy, just copy and paste an instance of this modifier to your new objects.

Finally, check out the map tree it creates in the material editor...



This map composites your three projections together. And check out each submap...



Especially notice the "Face Angle Threshold" area. This fades off the edges of the projection as the object's face points perpendicular to the projection camera. This replaces the need for 2 falloff maps in the "UVW Mapping Method". And since the fade-off is aligned to your projection cameras, and not to the object space of your individual objects, you don't need to reset the xform on your objects.

And the visual results it provides are identical to the "UVW Mapping Method"...



So in general, I would recommend using the "CameraMapGemini Method" for making your Blended Box Maps from now on. It's still not as good as a dedicated plugin (that I still hope someone writes one day), but it does fix all 3 of the major downsides to using the "UVW Mapping Method".

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