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arabellajones

A summary of what alpha channels do.

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There can be three textures applied to a face of an object, and what they all do can feel rather confusing: multiple web pages, snapshots of different moments in the history of SL.

 

Here's the path I took. I was in a bit of a grumpy mood about the organisation of SL documentation.

I was looking up how specularity is controlled, and I suspected alpha channels had a part in it. I didn't expect much here, but the links could be better. The next article I found was more specific, but was first posted in 2013, with an edit in 2018, but only deals with the alpha channel in the Specularity map. But at least there is a link to the Good Building Practises portal

That's a very general link, we're just getting a list of web pages to look though, on all aspects of building. "Texture Usage" is from 2013, and implies some features are still new. Not really relevant to the alpha channels. Case Study - Katana using normal and specular maps looks promising, but something odd is happening with the images. It might be my browser, but that doesn't exclude the changes in HTML over the last seven years. It's for the LightWave crowd, maybe assumes too much for the rest of us, and since there's a company make wifi-connected lighting using that name, maybe "LightWave 3D" should be substituted.

Finally i hit a useful page "Alpha Modes Do's and Don'ts". Suddenly I find an explanation of what the Normal Map alpha channel does, as well as a version of the Specular Map alpha channel that feels a bit different. I think it's the same, but some of the language is a little different. What is the " reflected environment map"? It seems to be synonymous with the sky, which might matter a lot more with what EEP is doing. The Normal Map Alpha modulates the Glossiness, the Specular Map Alpha modulates the Environment reflection. So you could have a flat surface using a normal map to produce a criss-crossing pattern of ridges, with the three alpha channels making the gaps transparent and different reflective: think of stained glass windows, You'd have to use Alpha Blending on the Diffuse Map, and I am not sure that has ever worked quite as described.

That page also introduces the idea of an "Emissive Mask", which seems to use the same alpha channel as the transparency... Turns out it's in the options for a Diffuse Map with an Alpha Channel, one of the set None, Alpha Blending, Alpha Masking, and Emissive Mask. Trouble is, if we use the story-telling analogy, somebody was thinking they were writing Hamlet, when they should have been writing a story for a grade school audience. I had to furkle around in my viewer when they didn't even bother with a picture.

Pictures tell stories too.

Screenshot_2020-07-02_15-37-28.png.30e9f6d33dc1a80d5a352bfcee4d6ad7.png

That could do some interesting things with an animated texture.

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It's at least 3 years if not more that I try to tell people about the use of the alpha channels when using materials textures, as opposed to relying on specular map only

http://wiki.secondlife.com/wiki/Material_Data

This is all you need to understand the whole thing. Scrolling down, you will find a nice table that summarizes it all (titled as "encoding") 

If you go to my little stall at builders brewery, there is an example of emissive mask material rezzed against the wall (a sci-fi lit floor material texture) 

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1 hour ago, OptimoMaximo said:

It's at least 3 years if not more that I try to tell people about the use of the alpha channels when using materials textures, as opposed to relying on specular map only

http://wiki.secondlife.com/wiki/Material_Data

The page is dated 2014. so at least 6 years...

The Default/Planar switch looks very odd. If you're on Default you can change the Repeats per meter, and the Horizontal and Vertical scale changes in proportion, but switch to Planar and the Repeats per meter box greys out and the Scale values change. It may be different on something which isn't a cube, or where the UV map of the face doesn't fill  the full 0 - 1 range. I stick with Default mode, and things can sometimes get strange if the UV map isn't very simple.

Screenshot_2020-07-02_21-57-59.png.11497faa147f006fe3978d8cf46ed66e.pngScreenshot_2020-07-02_21-59-02.png.69a56adb464bae5f8cfafafe4a8fa7d7.png

 

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2 minutes ago, arabellajones said:

The page is dated 2014. so at least 6 years...

So what? Data encoding doesn't change overtime or content breaks. Therefore, old or not, the content in that page is still relevant until the end of this shader model and a new one would be implemented, or new features being added on top (which still makes the base learning material incomplete, but still relevant). 

Planar mode has always been odd with materials, with each texture not aligning to the others by default, in FS there's a dedicated checkbox to sync them.

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When Planar mapping is on, the Repeats per meter box is greyed out. Yet your so brilliant explanation says this.

You're not making sense. How can you use a greyed-out data entry box?

Screenshot_2020-07-03_08-38-43.png.b8d616dace8a1b397f13a86563e19ff9.png

 

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Something else that would be useful: a rundown of the different side effects of setting transparency via Edit Panel UI and alpha channel.

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14 hours ago, arabellajones said:

Yet your so brilliant explanation says this.

The topic wasn't about the use of alpha channels? That's what I pointed you at. 

14 hours ago, arabellajones said:

You're not making sense. How can you use a greyed-out data entry box?

 

This is another question that came after the one I answered with my comment and link. Anyway, as far as I can remember, that data entry never worked to input a value. What I remember is that changing the regular repeat values updates the repeats per meter box, giving some feedback about this data. 

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I think you're just trying to wriggle out of the issue of the quality of documentation, a long running and widespread pattern of failures which is exemplified by the path shown in my original post.

Should I be writing at the Dick and Jane level? See Arabella try to find out how SL works. See Dick write.

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On 7/4/2020 at 10:14 AM, arabellajones said:

I think you're just trying to wriggle out of the issue of the quality of documentation,

No, I'm not. I'm with you about the clarity of the wording used in the docs, nonetheless I realise that it was written in a manner that requires some background understanding sitting in the back of your head to make sense of it. I understood this bit when I wrote my anim exporter. En doing didn't make any sense to me until I refreshed my high-school math classes about quaternions. Then it made sense. Texture encoding in this regard is the same, with someone writing about methods used in external 3d softwares and image management systems. This, about the thread topic. 

Now, about the derail you did about the mapping methods, notice how in planar mapping the repeats values match the repeats per meter greyed out field. Overtime, someone realised it was redundant and greyed out that control to show the result only, rather than using it as input method. Should you change the repeats non uniformly, the greyed out field would give you the result of mapping calculations as a hint of texture surface coverage. 

We all know how LL works, don't expect any better. It's not a company the size of Autodesk that releases a new full documentation at every release. As long as the base functionality is still reflected, documentation won't be updated to fix minor changes. 

2 hours ago, Kyrah Abattoir said:

Personally I prefer blaming people's inability to search and experiment.

And also this. 

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