Poser Skin Nodes: Spots

An Exploration of Poser Skin Nodes - Spots

These nodes - in their original form - were developed by BagginsBill of RuntimeDNA. Please note: this is *NOT* a tutorial... it is an exploration. I'm not an expert or even understand much about this. I just desperately want to understand. The purpose of this is to put my ignorance out there for all to see so that perhaps some extremely motivated or irritated knowledgeable person will set me right or point me in the right direction. So, that is the spirit of this undertaking: it is not an authorative work but a bit of a publishing the results of my little material room lab.

What is a Spots node? It's a 3D texture (New Node > 3D Textures > spots). Spot_color kinda says what it is, Size refers to the size of the spots, softness refers to whether or not the spots have hard or soft edges in relation to the background (base) colour and then we get to threshold.

To get the head around what Threshold's about, let's create a high-res sphere from the Poser Primitives collection. [Write me if you want that clarifying] Assign some materials to the top half and the bottom half of the sphere. To do that, you click on the Grouping tool icon on the Editing Tool bar: this brings up the Grouping Editor dialogue.

What I did to make the top and bottom half of the sphere different materials, I first went into Camera Front View. On the upper left of the dialogue I selected "New Group" and called it "Top". With my mouse, I press down on the left-mouse button and drag diagonally over the top half of the sphere: a rectangle develops covering the visible area (i.e., the area facing you) you are selecting. When I let go, the top half of the sphere is highlighted in red. I Click on "Assign Material" under Geometry Functions in that dialogue and type in the name of my new Material: calling it "Top Half". Voila, you've got a new material on the front of the top half of your sphere.

Do the same for the bottom half: I called the group "Bottom" and my material for that group "Bottom Half". I know: highly imaginative.

Do the same for the bottom half: I called the group "Bottom" and my material for that group "Bottom Half". I know: highly imaginative.

Image 1

When you do the back of the sphere, you can assign the selections to existing groups by first selecting the group from the dropdown (make sure the little plus buttom is orange at the top of this dialogue!) and then highlighting the geometry (polygons) you want to add to the group. Click on "Assign Material" and select the appropriate material from the dropdown - see image on the right. Do the same for the other half and you're done.

Be sure to check that you haven't assigned polygons to more than one group: in the middle of the dialogue you'll see a Show multigrouped faces tick-box... select it and spin your ball around. If you see any red, you'll need to decide which group that area belongs to, then with the other group selected and the minus sign selected, deselect by highlighting those polygons. This process is a PITA, and not very intuitive to do, but it will make the rest of this exercise very confusing for you to make more than one material assigned to a surface area.

Okay, let's close this Grouping Editor and start having some fun, hey?

Go into the material room (advanced) and if not already selected, from the object dropdown select Figure1 (or whatever your sphere is called). The material Preview will be selected by default. From that dropdown, chose "TopHalf". Cool, hey? You created this blank material: now, we're going to do something with it.

You already know how to create nodes if you read the main page of our little exploration, here: "An Exploration of Poser Skin Nodes" - if you haven't, please do. Dragging out from the Diffuse_Color input node, create a Spots node from the 3D Textures group. We'll leave all the values at their default settings. You should end up with something similar to the image on the right.

Select the BottomHalf material and assign a Spots node to it, only this time we *are* going to change one parameter (parameters are things like Base_Color, Spot_Color and so forth ... for the Spots node: it's the things you can change to make the node give off different values). We want to change the spot_color to black. Heck, let's try it and see what happens, hey? I don't think you have to, but I usually exit the material room when I do a render, so I did. And rendered. And produced Image 2:

Image 2

Image 3

Yep, I know, real exciting. Bear with me, because we have to walk along this path to kinda see why those nodes on the other pages exist in a skin shader. So, back in the material room:

...we'll make all our changes to the TopHalf material from now on... better lighting and all that. So, changing only one parameter at a time: let's have a look at the Softness parameter. It is set to "0" - set it to "1".

Whoa.

Okay, that's a bit extreme, let's try ".5". Sheesh. Okay, how about ".05"? (Image 4)

So, what are we doing here? We're getting a feel for the parameters themselves: how quickly a change in a given value will affect the output of the node. So, a very small change in the spots "Softness" parameter creates very big changes in the appearance of the spots. What's also quite evident here is that softening the edges of the spot also tends to shrink its overall size (based on what we see in the control hemisphere below the one we changed).

Image 4 ... Spots: softened to .05

So, let's reset Softness back to "0" and have a fiddle with the Threshold parameter. It is currently set to ".25". No idea what it affects, yet. We'll go ahead and set it to "1".

Oops. Now, the whole material is covered with red. Let's go the other extreme and set it to ".05". The upper hemisphere turns white - rendering shows no discernable colour at all.

".1" shows just a little. We'll render and have a good look at it. (Image 5)

So, okay, now we know what Threshold does. Kinda. What is interesting to note is that size of the spot decreases as the Threshold number increases... keeping in mind, here, that the spot colour is actually white, and the background colour is red.

Image 5 ... Spots: Threshold at .1

Now, let's mix and match. We haven't really fiddled with Spot_Size at all... been watching the spot's apparent size change with the Threshold and Softness parameters. So, let's set everything back to the way it was (Softness at "0", Threshold at ".25") and change Size to "8". (Image 6)

Well, it seems that those other two parameters don't really affect size at all: they must affect the borders of the spots and thereby appear to change the spot's size.

Well, this huge splotches on the surface of our sphere might have some purpose to someone out there, but what we want to know is: how does this work in a skin shader?

Image 6 ... Spots: Size at 8

Let's go back to that shader of Bill's we're studying and have a look at the Spots_3 settings. We've got:
Base_color: 229,229,229 (light grey)
Spot_color: 255,255,255 (white)
Spot_Size: .07
Softness: .7
Threshold: .5

WooHOO... let's try these on our sphere and see what happens! So go ahead and type them in and render. (Image 7)

How totally cool is that! Now, we can kinda see what Bill was trying to achieve and how Heather got her spots... err, skin texture variances.

Image 7 ...Spots_3: Bill's setting

Play with the numbers a bit (one at a time, please) and let's see what happens:
Base_color: 229,229,229 (light grey)
Spot_color: 255,255,255 (white)
Spot_Size: .04 (down from .07)
Softness: .7
Threshold: .5

Nice... larger spots... could be useful. Remember, the white bit is the spot, the grey, the background.

Image 8 ...Spots_3: size down from .07 to .04

Okay, let's try:
Base_color: 229,229,229 (light grey)
Spot_color: 255,255,255 (white)
Spot_Size: .07
Softness: .4 (down from .7)
Threshold: .5

Urk. No. Suddenly the texture is a bit too harsh for skin... thinking of our skin shader, it would give our character a complex, don't you think? Might be nice for texturing walls, though: we had interior rooms textured exactly like that back in California. That texturing hid a myriad of minor sheet-rock (gyp-rock, plaster-board, whatever-you-want-to-call-it) smoothing flaws.

So, we'll keep that setting in our little black book for future reference.

Image 9 ...Spots_3: softness down from .7 to .4

Just for laughs, we'll go ahead and do the Spots_2 settings next:
Base_color: 255,255,255 (white)
Spot_color: 255,239,239 (light pinkish)
Spot_Size: .105
Softness: .7
Threshold: .8

We've changed the spot colour this time, and the background is white. Very soft, very nice texture... extremely curious to see how this applies to skin.

Okay, we know what these spots do, now, let's use them in a sentence.

Image 10 ...Spots_2: Bill's setting

First, so that we have something to campare with, I did a render of Heather's face using only the textureMap plugged into the PoserSurface Diffuse_color channel, which is set to white.

...and your standard textureMap node set-up:

Then, a render of Heather's face using only the Spots_3 node (with Bill's settings, see above) fed by my texture map, plugged into the PoserSurface Diffuse_color channel, which is set to white.

The node set-up looks like this... note I set specular value channel to 0 on the PoserSurface node:

Then, a render of Heather's face using both the Spots_3 node and the Spots_2 node with Bill's settings fed by my texture map, plugged into the PoserSurface Diffuse_color channel.

The node set-up looks like this:

Time for a COFFEE BREAK