Functions Academy

[N-drju]

...knowing that you can achieve the same result with a merge node actually IS helpful. That is the beginning of a META understanding of how the nodes work. We have learnt that the ADD COLOUR node is part of the internal make-up of the merge node. (So is the MULTIPLY_COLOUR, MIX_COLOUR, SUBTRACT_COLOUR, DIVIDE_COLOUR and the scalar equivalents).

"why would I need a function to play with color then?" Because you could create a lighter weight scene than using the more complex (albeit more user-friendly)red nodes.

Oh, wait... I see now. So the functions you mention can be, in PF-related circumstances at least, used just like the merge shader options! Right...?

Like, I would have a specialized node that subtracts, screens etc. instead of a red node that contains all of them (and, by that fact alone, is heavy?)

I think it's a good idea to have a separate topic for each node or node family. Add Colour, Add Scalar and Add Vector are part of the "Add" family of function nodes.

(...)

If it helps, we can create a new forum section to provide a home for these. And since this topic has already started to become a discussion about more than just Add nodes, we could split this topic so that the Add nodes can be discussed on their own.

I wholeheartedly agree, and yes! Let's do it - another forum section, one topic per node.

However, I would rather like to see someone making a brief description of a node (like cyphyr did) and only then allow discussion.

[cyphyr]

Yes, exactly.
The red nodes that we use every day are complex combinations of the blue nodes all rolled together into a simplified user understandable interface.
(There's probably a bit more to it than that but true in essence).

[N-drju]

Ok... I reconsider - we did nail something.

@Matt - Thank you for considering this. Suggest creating a new board, name it like Attila did - "Function Academy" or anything along these lines.

[CredePendrel]

"That is the beginning of a META understanding of how the nodes work. We have learnt that the ADD COLOUR node is part of the internal make-up of the merge node. (So is the MULTIPLY_COLOUR, MIX_COLOUR, SUBTRACT_COLOUR, DIVIDE_COLOUR and the scalar equivalents)."

This is great! Thank you cyphyr! I learned something new today too that will actually prove useful and makes me feel like I am actually making headway!

[N-drju]

Right now, it makes me wonder which function translates into "Screen A" or something like that... Divide, multiply, subtract - understood. But "Screen"...?

(Which I frequently employ in "merge shader", mind you, and find extremely useful.)

[Dune]

Screen: I believe something then masked by the color input, as you can't mask by a displacement. But I must admit I never use(d) it (I use more simple blue nodes for masks and color additions and such nowadays).

[cyphyr]

I did a quick google of Photoshop Screen math and it came back with this (see attached)

photoshop-blend-modes-explained

All of this is possible with blue nodes although it's a little more complex than just ADD_COLOUR, but as a mental exercise it may yield helpful results.

Just tested it and it works

[WAS]

I think it's a good idea to have a separate topic for each node or node family. Add Colour, Add Scalar and Add Vector are part of the "Add" family of function nodes.

I can see some logic to the Multiply nodes being part of the same topic, but as more and more nodes are discussed we will need some criteria to separate them.

So I'd recommend one topic for Add Scalar/Colour/Vector, another topic for Multiply, another for Trigonometry functions, and so on.

If it helps, we can create a new forum section to provide a home for these. And since this topic has already started to become a discussion about more than just Add nodes, we could split this topic so that the Add nodes can be discussed on their own.

This is actually a pretty good idea with the lack of documentation. We could have a forum, where posts should only pertain to nodes, and than discussed in those topics. Like you said a "Add Functions" topic, which can discuss what the functions do in a basic manner, and than elaborate with community discussion of uses.

Is that sort of what you meant @Matt ?

Maybe the forum could be called Node Reference so it can encompass more than just functions.

Not to cut anyone out though, maybe the forum should encompass a new user group, where only users added this usergroup (Tutors?) can create topics, to keep things as categorized as possible and on point. Anyone can reply though.

[WAS]

I did a quick google of Photoshop Screen math and it came back with this (see attached)

photoshop-blend-modes-explained

All of this is possible with blue nodes although it's a little more complex than just ADD_COLOUR, but as a mental exercise it may yield helpful results.

Just tested it and it works

I didn't catch this! I knew that our functions didn't act exactly like Photoshops filters (like Multiply in TG is an actualy multiplication where Photoshop is more of a subtract/darken) where darks are applied multiplied, and white isn't effecting the layer (in photoshop)

Also about your comment on disagreeing right back, you don't really provide a justified response to my claim. What is your scene? What is it plugging in it? Does it need to be part of the scene entirely or is part of something else built and than applied to the scene? Just like Photoshops documentation on it's filters, they do not show you redundancy, they explain the filters, and leave it to you, because now with a understanding of the filters, you should be able to use them in any means you like.

When what you do with it entirely depends on your end-goal, and the use of it so open it can be used for almost anything, you most certainly do not go into detail about that. You cover it's in and outs, and leave it at that. No anyone can use it any way they like with that understanding. If they still don't understand, THAT's where How To books and Tutorials come into play.

[cyphyr]

The problem with Photoshop is that it has been our base line "goto" for so many years. It is our standard reference point, images are said to be shopped etc. Trouble is it's not very up to date. you have to jump through hoops to get it into a linear work-flow and than half the plugins don't work lol.

...
I didn't catch this! I knew that our functions didn't act exactly like Photoshops filters (like Multiply in TG is an actualy multiplication where Photoshop is more of a subtract/darken) where darks are applied multiplied, and white isn't effecting the layer (in photoshop)

The functions in Terragen are linear and work in a relatively simple mathematical way (so multiply works as you would expect it to for example).

Also we have to remember that in Photoshop colours have values of combinations of three channels (RGB) of 0 - 255 each channel.
In Terragen (and Nuke and I guess most linear work-flow software) the colour channels can have any positive or negative value. The maths still works.

[WAS]

The problem with Photoshop is that it has been our base line "goto" for so many years. It is our standard reference point, images are said to be shopped etc. Trouble is it's not very up to date. you have to jump through hoops to get it into a linear work-flow and than half the plugins don't work lol.

...
I didn't catch this! I knew that our functions didn't act exactly like Photoshops filters (like Multiply in TG is an actualy multiplication where Photoshop is more of a subtract/darken) where darks are applied multiplied, and white isn't effecting the layer (in photoshop)

The functions in Terragen are linear and work in a relatively simple mathematical way (so multiply works as you would expect it to for example).

Also we have to remember that in Photoshop colours have values of combinations of three channels (RGB) of 0 - 255 each channel.
In Terragen (and Nuke and I guess most linear work-flow software) the colour channels can have any positive or negative value. The maths still works.

Huh, when I do multiply in Photoshop there is a lot more colour burning going on, especially for a 0-255 range compared to TG where I can multiply and get consistent colour results where the colour is multiplied in it's hue range without saturating/de-saturating the colour.

If they're entirely similar, I wonder why we don't have more filter modes in TG considering the use of them in PS.

[Matt]

Huh, when I do multiply in Photoshop there is a lot more colour burning going on, especially for a 0-255 range compared to TG where I can multiply and get consistent colour results where the colour is multiplied in it's hue range without saturating/de-saturating the colour.

Photoshop doesn't work in linear colour space by default, it works in gamma space. That causes hue, saturation and value to react a bit differently than they should.

[Matt]

This is actually a pretty good idea with the lack of documentation. We could have a forum, where posts should only pertain to nodes, and than discussed in those topics. Like you said a "Add Functions" topic, which can discuss what the functions do in a basic manner, and than elaborate with community discussion of uses.

Is that sort of what you meant @Matt ?

Yes, that's kind of what I meant. I wouldn't want to dictate how the discussion occurs, but just keep each topic focused on a particular node or node family so that it's easy to find. Then we could draw useful information from that to add to the Wiki.

Maybe the forum could be called Node Reference so it can encompass more than just functions.

That name isn't ideal because it we already have a Node Reference in the Wiki: http://www.planetside.co.uk/wiki/index.php?title=Terragen_Node_Reference

I think the two sources can complement each other, but need different names.

[WAS]

This is actually a pretty good idea with the lack of documentation. We could have a forum, where posts should only pertain to nodes, and than discussed in those topics. Like you said a "Add Functions" topic, which can discuss what the functions do in a basic manner, and than elaborate with community discussion of uses.

Is that sort of what you meant @Matt ?

Yes, that's kind of what I meant. I wouldn't want to dictate how the discussion occurs, but just keep each topic focused on a particular node or node family so that it's easy to find. Then we could draw useful information from that to add to the Wiki.

Maybe the forum could be called Node Reference so it can encompass more than just functions.

That name isn't ideal because it we already have a Node Reference in the Wiki: http://www.planetside.co.uk/wiki/index.php?title=Terragen_Node_Reference

I think the two sources can complement each other, but need different names.

My concern here is the Wiki does need serious updating, and isn't user accessible like tutorial forum and other threads tell users, so I was thinking this forum, and why it's named as such, is it's a placeholder for this content to be added to a revised wiki, like you said.

There is already misconception of uses/where to go, and this one would be at least new, current, and community driven (and inherently shouldnt be confused with official sources).

I'm also concerned with users just posting help topics there or starting discussions in a weird non-focused manner where the topic is hard to distinguish it's goal as a node doc/ref and why I feel users that will stick to this goal should be allowed to start topics. Anyone can reply and contribute. It would save moderation and topic moving imo

[WAS]

Huh, when I do multiply in Photoshop there is a lot more colour burning going on, especially for a 0-255 range compared to TG where I can multiply and get consistent colour results where the colour is multiplied in it's hue range without saturating/de-saturating the colour.

Photoshop doesn't work in linear colour space by default, it works in gamma space. That causes hue, saturation and value to react a bit differently than they should.

This makes sense, thanks for the explanation.