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18. May 2011

 

We 354px-Cartesian-coordinate-system.svgare all familiar with 2 dimensional Cartesian coordinates for describing positions in 2D space, often used to represent pixels on screen, but ultimately the very foundation of algebra.  The two values, x and y can be thought of to represent Left <-> Right and        Up <->Down respectively, at least when dealing with two dimensions.  But when you throw one more dimension in the mix, it gets a bit trickier.  I mean sure, coming up with Z as the label wasn’t exactly rocket science, but what does Z represent and here is where everything goes to hell!

 

 

 

See, there are two schools of thought on this subject and unfortunately both make perfect sense.  On one hand, one group views X,Y as already representing Left/Right and Up/Down on a computer display, so the most logical conclusion is that Z should represent depth.  Imagine for a second if you could reach INTO your monitor… that would be the Z coordinates.  If you have already done some 2D graphics work, X and Y are probably pretty well entrenched in your mind as representing screen position, so this probably makes a lot of sense to you.  For the record, this type of coordinate system where Z represents depth is referred to as a Y-up as Y represents the up direction.  Personally, this is the most intuitive to me.

 

 

But then there are these other types of people in the world… engineers and architects and to them X,Y are viewed in a much different context.  See instead of thinking in terms of a computer monitor in front of them, they think in terms of blueprints on a table.  With a system 300px-Z_axislike Autocad, the Z-axis is added when the blueprint is extruded in the 3rd dimension.  Think about it in terms of building a house from a floor plan, the X,Y coordinates represent the layout of everything on your floor, then Z represents the distance of things UP from the floor.  So, to a CAD person, it makes complete sense for Z to represent “UP” and Y to represent “depth” like in the figure to the right.  This obviously is referred to as Z-up.

 

 

 

 

 

Now you may be asking yourself… how exactly does this affect me?  Well, that’s an easy one… all kinds of tools work with a different axis set.  Of the 3 we use, Wings 3D is Y-up, Blender is Z-UP and Unity 3D is Y-up.  So… as you are creating your assets they spend a lot of time flipping around between programs!

 

With Wings 3D, if going directly to Unity, you are in luck, no more work has to be done.  Most of the time though, we will be going from Wings to Blender first.  Fortunately this fix is pretty easy.  When you export your model ( via the menu File->Export->Collada ), click the little box icon to bring up options.  Then make sure you select “Swap Y and Z axis” checkbox as shown in the picture below, then OK and export.  This setting is “sticky” so you should only have to choose it once.

UntitledSetting Wings 3D to export Z-up friendly

 

 

 

 

 

 

 

 

Now in Blender things get a bit trickier and therefore it’s really easy.  Frankly, there is nothing you can do.  The axis system is fixed so you can’t change that, and there are no options when exporting.  I suppose you could model everything rotated but that would add a great deal of confusion.

 

 

So that leads us to Unity, currently the importer (version 2.57b ) is working properly, so thankfully you *shouldn’t* have to do anything, it automatically rotates it for you.  That said, this importer isn’t always the most… stable thing.  In cases where it doesn’t import correctly, you have one of two options.  First you can rotate manually 90 degrees about the X axis when you create an asset in Unity.  Otherwise, you can perform the conversion as part of the import process by creating an AssetPostProcessor which is a script run during the importation process, allowing you to make last second alterations.

 

 

 

For the record, this isn’t only a Blender/Unity problem, Max, Maya and Softimage are all Z-Up modelers by default, while I believe Cinema 4D is Y-up.  It is something to be aware of when moving from one application to the next. If it seems like your model is doing a backflip, the axis difference is most likely the cause.

Art


11. May 2011

 

So I finally got around to moving from 2.56 –> 2.57 and apparently it some API changes seem to have broken the Unity importing.  In my case, once saving the .blend file to my assets directory I get an error message of “Blender could not convert the .blend file to FBX file”. The solution was found on the Unity forums in the post by user Woodn.  For simplicities sake and due to the importance of this fix, I will repost it here.  Again, all credit goes to woodn for compiling this fix, and to alewinn and jorrit.  Thanks!

 

Ok, collecting all infos until unity is updated officially:
Credits go to jorrit and Alewinn!
Mac:
- Get Blender 2.57a from blender.org or a recent build from graphicall.org and unzip it somewhere. Assign blend files to open with the just downloaded blender.app.
- Browse to the Unity folder and right-click "Unity.app" and select " Show Package content". Then browse to the folder Contents/Tools/ and backup "Unity-BlenderToFBX.py". Then replace it with the one in the attached zip file or change the lines described by alewinn a few posts above yourself.
- Done.

 


Win:
- Get Blender 2.57a from blender.org or a recent build from graphicall.org and unzip it somewhere. If you use a zip package, make sure you register the blender.exe by executing "blender.exe -r" in a cmd prompt or with a shortcut. If you use the installer, you don't need to do this.
- Browse to the C:\Program Files (x86)\Unity\Editor\Data\Tools folder and backup "Unity-BlenderToFBX.py". Then Replace it with the one in the attached zip file or change the lines described by alewinn a few posts above yourself.
- Done.

 

Once I replaced the .py script and restarted Unity, everything worked normally again.

File attached below.

Unity-BlenderToFBX.zip (903.00 bytes)

Art


30. April 2011

6a00d8341c858253ef00e54f2306618834-640wiSo, choosing Blender for my art pipeline has some very big upsides, and a couple massive downsides.

 

Amongst the biggest downsides is that Blender is in the midst of a very long move from 2.4x to 2.5x, which means you are effectively using beta software in production.  Frankly, the 2.5x branch is probably as stable as the 2.4x branch with some major feature improvements.  That said, there is a giant downside… all kinds of documentation is simply and massively WRONG.

I just spent 2 hours trying to get a textured model into Unity, and for the love of all that is, I simply couldn’t get textures to work.  After many google sessions, I read that TexFace needs to be enabled… simply press F5 or F9, but again, these instructions are for 2.4x and are outdated.

I finally found the way after much confusing.

Properties->Material Icon ( the Ball )->New Material->Assign, then scroll down to Options and click Face Textures.  Done.  That was intuitive now, wasn’t it?

 

The following video illustrates that process.  Again of key note If you are using Blender with Unity, your textures WILL NOT WORK if you do not follow this process.

 

Enabling TexFace in Blender 2.56

Art


29. April 2011

I just received the following email and thought I would pass it on.  I’ve received a few of these offers, so if you are looking to purchase in the future, wait for the next promo.

 

Greetings,

At Unity, we love games and want to see your game on mobile devices. To help get your Unity-powered game live in the App Store or available on any of the 30 million-plus Android devices out there, we are offering you a 20% discount on your purchase of a Unity iOS or Unity Android license. Simply visit our online store by April 30th and enter UFRM0430 when asked for your Rebate Code.

Unity Mobile - 20% off

Enjoy,
The Unity Team

Both links edited as they contained tracking info linked to my email address.

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