How does Unity handle alpha sorting?

Question

We've written an MOV material that plays a PNG compressed MOV file with alpha on a poly. It's pretty cool though a little memory intensive. Not a problem for this application.

Here's the problem/question:

Problem: I'm seeing alpha flutter between two polygons that overlap each other in the game camera. The distance between them is way more than it needs to be to avoid Z-Buffer artifacts so nope, it's not that.

Question: How does Unity decide which pixels of an alpha texture to display? Is it by object center or object bounding volume?

Here's what we're trying for: http://www.lindsaydigital.com/clients/MBAQ/webPlayer/test_006.html

Answer 1

Best Answer

Answer by jonas-echterhoff · Dec 14, 2009 at 09:30 PM

One thing which may be helpful here is to use non-standart render queues in your shaders. If you replace

Tags {"Queue" = "Transparent" }

with

Tags {"Queue" = "Transparent+1" },

that material will be rendered after all normal transparent materials.

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spencer lindsay · Dec 15, 2009 at 09:13 PM 0

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Cool. As in the skybox shader, right?

Thanks Jonas.

jonas-echterhoff ♦♦ · Dec 16, 2009 at 08:56 AM 0

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well, the skybox shader uses "Queue"="Background" to make it render before all others. But, yeah - this is how you can manually change render order.

yoyo · Jan 06, 2011 at 07:35 PM 0

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You can also set material.renderQueue, which avoids having to create multiple copies of the shader when you need multiple sort orders.

Answer 2

Answer by spencer lindsay · Dec 14, 2009 at 09:22 PM

The answer seems to be: "Bounding Volume".

I added a triangle to the object I wanted to be in front and moved it out towards the camera, making the bounding volume of the smaller, "front" object larger than the background object. It's a hack, but it works.

Spence.

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How does Unity handle alpha sorting?

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