A matte object is geometry identified by the HP Reveal engine as having a special rendering method - that method being not to render any digital content it at all.
Using matte objects it's possible to create the effect of a hole containing a large space inside - like a window (or the Tardis!). You can use them to represent objects in the real world - say a room with pillars - so that your 3D content will appear to pass behind them, instead of being drawn on top of everything.
Matte objects will occlude all content in an Aura listed above it in the overlay list - not just the models in the same dae file. Usually you will want your matte object to occlude everything in the Aura, so drag & place it at the bottom of your Overlay list in the Studio.
Start by creating some geometry, here I have made a basic sphere. Around that I have created a box & cut a hole out in the centre of one of its faces.
I have left the sphere as its default green colour, what is important is that I've applied a material to the box that has the name "matte". The material name is all the HP Reveal 3D player is looking for & if an object in the scene has a material with the name "matte" the engine knows to render that object differently.
All of the other material parameters are ignored - so changing anything else here will not have any effect.
Next export the scene as an OpenCollada type dae. You can download the OpenCollada dae exporter for 3ds Max or Maya here.
If you've used Maya to create your dae file - then that is it! Follow the creating a tar file steps & upload your model to the Studio.
If you were using 3ds Max, there is an additional step you need to take. Locate the dae file in your file browser & open it up with your text editor of choice - we suggest Notepad++.
You simply need to locate the line which defines the properties of the matte material - the quickest way to do this is just to hit ctrl+f and search for "matte".
All you need to add is: name ="matte" to the inside of the effect id tag.
Hit save and you're ready to package it up as a tar file & upload to the Studio.