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#1 Noisycricket

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Posted 18 November 2010 - 12:42 AM

I wanted to make a dog/wolf model for a little atmosphere. I found this tutorial which looks like it would give great results if it will work. Basically it involves putting several 2d sprites around the dog. Would i be able to have several unconnected sprites around the dog model, or would they have to be connected to the dog model to work?

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#2 rich_is_bored

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Posted 18 November 2010 - 02:43 AM

You don't have to connect the alpha mapped polygons to the body of the wolf. They will animate with the rest of the model just fine.

The bigger question is transparency. With id Tech 4 you only have three options and none of them are going to yield results like you see depicted in that tutorial.

The first option is the translucent material shader keyword. No alpha maps are used, the entire surface is rendered at 50% opacity, and you maintain light interactions. This won't be of any use here. It's better suited for things like glass windows.

The second option is the "blend" blend mode. Alpha maps are used here to their full 8-bit capacity but you lose light interactions. That means whatever colors you paint in the texture are what you will see in game. It's rendered at full brightness, i.e. red hair glows red even in a pitch black room.

The last option is alpha test. Alpha maps are used here as well but they are reduced to 1-bit images essentially making them behave like clip maps. The plus side is that you maintain light interactions.

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The problem is demonstrated well in this image from the tutorial. You paint an alpha map like that on the left and end up with a result like that on the right.

This is one of the first things I'd like to see get sorted out when the engine goes open source. Transparency in id Tech 4 is nasty.

#3 Noisycricket

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Posted 18 November 2010 - 10:11 AM

If i used only a fur color of 0,0,0, (totally black) would that make the interactions with light and shadows look ok? Thanks for the detailed answer Rich.

#4 OrbWeaver

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Posted 18 November 2010 - 10:46 AM

If i used only a fur color of 0,0,0, (totally black) would that make the interactions with light and shadows look ok?


It wouldn't look black like a black dog's fur, it would look black as in "completely black on the screen no matter what", like the staff in Robbing the Cradle.

#5 nbohr1more

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Posted 18 November 2010 - 11:03 AM

That might work if accompanied by some wispy specular maps... hmm... :huh:

Edited by nbohr1more, 18 November 2010 - 11:04 AM.

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#6 Tels

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Posted 18 November 2010 - 02:28 PM

You don't have to connect the alpha mapped polygons to the body of the wolf. They will animate with the rest of the model just fine.


We already have a commoner head model with some hair, you could ask Springheel how he had done it. I thin since the fur is mainly black, you can possible get away with alphatest if you use it for only some sprites along the body to provide the silouette - the base fur will still be rendered ok.

This is one of the first things I'd like to see get sorted out when the engine goes open source. Transparency in id Tech 4 is nasty.


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#7 Serpentine

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Posted 18 November 2010 - 02:36 PM

You can get coloured alpha blending with faked lighting via specular. however you have to use half depth alpha, which isnt too bad for something like this.

I suspect you could even reuse the alpha for specular and tone it down. However I'm unsure as to how this would all act with HDR and postprocessing so I haven't really gone much farther down the road.

Otherwise you can use an alphatested surface with 2nd blend stage ontop of that to soften the edges, however the edges wont react to light at all.

#8 rich_is_bored

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Posted 18 November 2010 - 04:05 PM

If i used only a fur color of 0,0,0, (totally black) would that make the interactions with light and shadows look ok? Thanks for the detailed answer Rich.


OrbWeaver is right. Like I said above you lose light interactions completely when you use the mode "blend". Black is less noticeable but it's still very unnatural looking.

That might work if accompanied by some wispy specular maps... hmm... :huh:


Nope. Specular reflections are light interactions. Black is still black.

#9 Noisycricket

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Posted 08 December 2010 - 03:57 PM

I ran into two examples on transparent black hair, one actually in Doom 3 and it doesn't look bad at least in dark environments. The other is in Fable 3, and i can't tell if light is affecting it, it almost looks like its not. Since modeling the wolf was just for fun and to learn Maya, i may just make it, or part of it to test.

Fable3( at 2:20 )

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#10 Springheel

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Posted 08 December 2010 - 05:01 PM

That's just a black texture like the one posted earlier, with a "blend" filter applied.
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