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Thread: Nodal concepts/theory explanation??

  1. #1
    Axes grinder- Dongle #99
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    Question Nodal concepts/theory explanation??

    I find nodes really hard to wrap my head around, especially the "SpotInfo" type nodes, and especially the use of same in Displacement.

    Anyone got links to a nice clear explanation of what's going on in there? I'm not looking for a tutorial, but something that will cover the concepts of the whole nodal..... thing.

    Thanks!
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  2. #2
    So you want someone to write an explanation of the whole of the nodal system? Uhm no

  3. #3
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    Quote Originally Posted by jeric_synergy View Post
    I find nodes really hard to wrap my head around, especially the "SpotInfo" type nodes, and especially the use of same in Displacement.
    In Object Displacement context the only things in Spot Info that are useful are Object Spot, World Spot and Normal. The others are meaningless not initialized.

    Anyone got links to a nice clear explanation of what's going on in there? I'm not looking for a tutorial, but something that will cover the concepts of the whole nodal..... thing.
    Weird question. It's like asking for concept of mathematic. Who needs mathematics, knows it.
    Example from real world - you have room that needs wood plank floor, so you have to use math to calculate how many planks buy in shop, and multiply width * height of room + some spare..
    The same is with nodes- you need to change color or attribute f.e. distance to other element(s) in scene, so you're using Math > Vector > Distance.. etc etc
    if distance == 0.0 has to give red, and distance == 10.0 m has to give blue, then you're using output from Distance node as input to Gradient. etc. etc.
    Whatever you like in wanted by you order..

  4. #4
    NewTek documentation wrench's Avatar
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    And besides, explaining the Spot Info node theoretically is like explaining Quantum Physics - a spot is an area of an image occupied by a surface in an image that has not yet been rendered and so does not exist yet.

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  5. #5
    Goes bump in the night RebelHill's Avatar
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    The concept of nodes is kinda self evident is it not?? I mean the "concept" is basically the same as what is more commonly known as a "flow chart"..

    what is it you don't get about this concept?
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  6. #6
    Professional Newbie funk's Avatar
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    I have the basics down with nodes, but yeah stuff like spot info still has me confused.
    The LW docs havent helped at all. What Id like to see is usage examples! No better way to learn
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  7. #7
    Cow Orker cagey5's Avatar
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    Quote Originally Posted by Sensei View Post
    Example from real world - you have room that needs wood plank floor, so you have to use math to calculate how many planks buy in shop, and multiply width * height of room + some spare..
    If that's your equation for calculating floor area then I'd stick to the day job..
    Last edited by cagey5; 01-14-2011 at 04:11 PM.
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  8. #8
    Goes bump in the night RebelHill's Avatar
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    Well, spot info for example, is pretty clearly described in the manual...

    -------------------------------------------------------------------------

    "First let’s define what a “spot” is. A spot is just a spot - a fleck, a
    pinpoint. You can think of a spot as a single element area that is
    calculated or evaluated, on a surface and that is arbitrary in size. Any
    given spot contains several types of data including color, normal
    angle, the direction that a ray is coming or going from relative to that
    spot, and etc.
    Remember Node Editor is a surface texture and shading editor so the
    word spot here pertains to the spots of an objects surface. Spots are
    a useful primitive type for texture design, because, in general, the
    relations between features of the spot and features of the texture are
    straightforward."

    ------------------------------------------------------------------------

    So from that, we can see that a "spot" is basically just that, a spot on the surface of a mesh... You can evaluate a spot to take information from it, colour, normal, etc.. and use that info/value to plug into other things... Or you can just use the info of which spot is being examined to apply something, colour, displacement, whatever to that spot of the mesh...

    But how to know which spot is actually being examined... well the truth is... all of them... every possible spot on the surface of that mesh. Ok, yes, taht would be infinite... so for the majority of purposes, since the meshes we use are made out of polygons, each spot can be thought of as a single polygon.

    So in the case of displacement, for instance... You apply a UV map to the mesh (which is fitted to the mesh via its UV co-ords), and the spot info measures the normal direction of every spot, on every polygon, to tell LW which direction the displacement should be pushed away from the surface at each of those "spots".
    Last edited by RebelHill; 01-14-2011 at 04:24 PM.
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  9. #9
    Cagey I hope your day Job isn't selling wood flooring, as that's exactly how you do it

    it's really difficult for many of us to explain the how's and wherefore's of Nodes. Quite often I open node flows and have no idea what they are doing, and have to work it out. Most of the time, it's just about maths nodes, and the point of them. I certainly never did vector maths in 3D at school (well it was so long ago, I can't remember if I did hehe). so it's hard to get your head round a lot of it, and even when I do, I then find it really hard to re-explain it back, because I understand it on an artistic level.

    The spot node is probably one of the most complex nodes in the system, so it's a difficult one to get! it's multifunctional, and each output is for a different type of thing!

    Think of the spot node as a 'get info about here' node.The type of data that's being got is colour coded in LW. Blue is vector information (xyz), red is colour (rgb) green is scalar (single channel, grey-scale), and pink is a integer (whole number). These bits of data are often used in other things, without having to get them from the spot node, you can do some unique things with these little bits of 3D scene information.

    With the vector data points, You can find the world space or local space of a bit of geometry, and then transform that, or use it to drive a texture, or move some geometry. find out where a ray is coming from, or going too, or measuring between objects of other points in 3D space. Normals are the direction a surface is facing, which is important for doing stuff like displacement, multiplying it with a texture height to get a displacement from the normal, rather than a single direction. Most shaders and 3d textures with bump output already assume the normal information anyway, but it's useful to be able get back to it for surfacing.

    The pink integer outputs are really interesting for rendering mostly, because they pertain to specific data about rays which fire child rays, in ray casting or ray-tracting functions. for example. if a ray is reflecting in a scene, it might recurse a number of times off reflective or radiosity bounces, or through transparent objects, from he camera. because we can get at that spot info we can transform it or use it to drive anything that effects, like controlling the colour of child rays, adding or subtracting information. They all do the same basic things, 'bounces' being generic and the others pertaining to specific things, and it's what I use to do some reflection bluring optimisation tricks, using either gradients or logic nodes (telling a ray to return X after N bounces limits the recursion independently of the global ray recursion setting.

    Trouble is I only know what I've thought up uses for, and there's a load of extended spot info nodes to do things I don't understand either. Like most people I just picked up a bunch of tricks

  10. #10
    Valiant NewTeKnight Matt's Avatar
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    I asked about the SpotInfo node in a thread quite a while ago (before I joined NewTek) and someone kindly explained what each of the outputs meant in lamen terms, I've tried searching for it, but I can't find it.

    Edit: It was probably you Tobian!

    One of the things I really want to do is create more diagram based explanations of more difficult concepts in LightWave, and this would extent to nodes.

    It's just finding the time! Here are some examples I found that I did that shows the kinda of explanations _I_ would want to see (some are not node related)

    Bear in mind these were done when I was on "the other side" Are probably out of date now, were never finished (hence the crap layout) but you'll get the idea!
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    Last edited by Matt; 01-14-2011 at 09:16 PM.
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  11. #11
    Nah there are people who understand this stuff much better than me, and I don't know what they all mean it doesn't help that they aren't even all in the manual, because they increased the number of outputs since 9.0 Maybe they can do an expanded explanation for the 10 manual

  12. #12
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    They're explained in LWSDK/html/classes/shader.html

  13. #13
    Profesor Pixel Poo Mr Rid's Avatar
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    Quote Originally Posted by jeric_synergy View Post
    ...something that will cover the concepts of the whole nodal..... thing.
    Lemme know when you find it. I continue to scratch my head over nodes, poking at them with a stick til something happens. Here and there are scattered tuts and posts that usually describe how to achieve one effect. Its like a crate of curious components with wires and doodads hanging off each, dumping them on the floor and trying to figure out what plugs in to what in order to do huh?
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  14. #14
    Axes grinder- Dongle #99
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    Quote Originally Posted by Tobian View Post
    So you want someone to write an explanation of the whole of the nodal system? Uhm no
    If your reading comprehension was adequate, you would have perceived that I was asking for links to existing explanations. So, STFU if you can't help.

    Meanwhile, several people here have stated they also have troubles with nodes, so it's not like I'm alone.
    Last edited by jeric_synergy; 01-15-2011 at 01:53 AM.
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  15. #15
    Valiant NewTeKnight Matt's Avatar
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    Quote Originally Posted by jeric_synergy View Post
    So, STFU if you can't help.
    He just did help, calm down Jeric, no need to start a fight!

    Group hug everyone!
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