DX Opacity Bug

[Tiros]

It's a thing I've been bothered by lots of times, and for quite long.. the DX Opacity bug. What happens is simply that while something's transparent, everything behind it will also be hidden. As shown in the following picture where I simply tried to throw together some quick volumetric grass:




So, what I'm wondering is.. is there some kind of fix/patch to solve this problem? Rather than rendering it.. I know It'd work properly while rendering, but that still won't solve the DX Bug

Cheers & Thanks in advance!

[TheoLogic]

ZBuffer problem. Actually, you have to render from the back to the front to avoid this. Sort the buffer to the camera and this will be fixed.

[doylle]

Well, like theologic said, it's a zBuffer problem. I know i said it was a bug, but it's not a real bug that you can fix, it's just a bug because there's no real workaround to get it fixed in max as far as I know.

the problem is this. When a scene is rendered, DX will look at the ZDepth of every face for each pixel. For every object it'll check the zDepth first, and determine if an object closer to the camera has already been rendered, or if that object is in fact the closest to the camera. (all per pixel) If it is is not the closest object to camera (and therfor another object is blocking it's visability), it will not render what's behind it... So if you then apply transarency to the object (this happens in a later stage during the rendering), you will have the effect you see in your screenshot...

The logical solution would be to sort all your grass planes, from far to close, and render them in that order. but that's not possible in max (again, as far as I know).

If i'm not mistaking then you're using the viewport shader i wrote. I think i'll work on an updated version soon, have a few things i want to add to it. I'll look some more, maybe i'll find a way to fix this

[Tiros]

Ah, that explains it then :/

Well, searching for dx opacity bug fixes on google didn't turn up any results, and I guess this is why.. I'll see if I can find anything about sorting the zbuffering though

And aye, I'm using your shader D, and if you'd be able to add a fix for it, I'd be forever grateful

Thanks for taking your time guys.

Cheers!

[Talon]

You could try making it 1-bit alpha.

Not sure how Max does it, but a fair few engines render 1-bit stuff in with the opaque stuff, rather than with the transparency pass. *shrug* Worth a try.

[Tiros]

Thanks for the tip Talon, but I'm afraid that didn't solve the problem, only made it look even more horrible

Cheers!