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Alpha maps

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Alpha maps

Postby Chett » Sat Oct 03, 2009 5:20 pm

If someone has time to write a bit more tutorial wise on alpha map generation it would be really nice.
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Postby Aaron » Sun Oct 04, 2009 1:58 am

Hi Chett,

Can you give me a clue as to what you'd like to see added to the alpha map user guide? I've not had many users asking for additional help for this feature, so it's not easy for me to guess what further questions need to be answered.

Cheers,
Aaron.
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Postby Chett » Sun Oct 04, 2009 1:08 pm

Well my first couple of tries didnt get anything to close to what I needed in the way of alpha maps, but that might well be lack of understanding on my part so I think I will hold up until I have made a few more attempts and have some specific ideas about what is needed.
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Postby Chett » Tue Oct 06, 2009 2:40 am

OK I worked with the alpha maps some more and I am still a little perplexed.
The basic 'generate alpha' seems to have no options or settings, with my current climate and terrain I have 8 textures so I get 2 alpha maps. I really need 1 with the textures reduced - all grasses as 1 id, rock as second etc.

Of course I could regenerate with a different climate definition to get that (and I probably will).

The alpha express with its filters looked at first like I could use that to get what I needed but I guess I dont understand it. Using 3 filters,
grass
sand (included dirt and mud)
rock (include cliffs etc.)

I got a map that just had the sand.

I changed the order putting sand last and got blank transparent.
I used GIMP to look at the produced file, does not appear to have layers.

So I guess what I am looking for is a better explaination of how the alpha express is supposed to work so maybe I can use that and not wind up with a version control problem using 2 different climates to get the alpha set-up I need.
Chett
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Postby Aaron » Tue Oct 06, 2009 10:44 am

Hi Chett,

The basic 'generate alpha' seems to have no options or settings


As the user guide explains, in the the 'combine alpha layers' wizard, you can combine alpha layers (e.g. all grasses as one layer, all rock as another, etc.). To combine layers, click in the 'alpha layer' column and select the ID of the layer to be combined. Please let me know if you have any problems with this.

Best regards,
Aaron.
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Postby Chett » Wed Oct 07, 2009 2:30 am

See I figured I was doing something wrong. Could have sworn I clicked on everything on that screen looking for setting :P Thanks

I am still curious about how the alpha express is supposed to work.
Chett
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Postby Aaron » Wed Oct 07, 2009 10:26 am

Hi Chett,

The expected behaviour of the 'Alpha export express' plugin and the filters is described in the documentation for the atFilterAM plugin.

Since the filtering operation uses an alphanumeric comparison, the the content of the maps output by the filter will depend on the names of the land types and the strings provided in the filter layers. For each pixel, the the first filter layer in the list to have a string that matches the land type name will be set as the output land type. If no filter layer matches the input land type, the output land type is left unassigned. To ensure an output land type is assigned, the wildcard string '*' may be used to match a layer against any land type. Obviously the wildcard should only be used for the last layer in a filter, as subsequent layers will never be tested.

Best regards,
Aaron.
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Postby Aaron » Sun Apr 11, 2010 1:15 am

Hi All,

In response to another question regarding how to use the 'Alpha Export Express' feature, I have updated the documentation for this feature. The main problem, it seems, is that the exporter is producing seemingly all-black images. As explained now in the docs, this is because users have selected 4 layers/image (RGBA), but the filter they have selected is producing only 3 layers. In this case, the 4th channel of the output image (alpha) is set to zero everywhere, which is the correct behaviour for texture splatting. However, this is interpreted by image viewing programs as meaning the image is totally transparent. Consequently, whilst the image is 'correct' for texture splatting use, it appears as being totally empty in image viewing programs. If this unnerves you, you should select the '3 layers/image' option, which will produce RGB output images without any transparency.

Cheerio,
Aaron.
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