Tag: Material Room

By switching ON the Shadow Catch Only option in a PoserSurface definition the surface will disappear completely, except from the shadows cast from other objects, and from itself as well.

Generally, this feature is used to create a render that blends well onto another image with objects around, and this is a way to transfer the shadows from objects in the Poser scene to the other objects in the background layer. The background objects are recreated in the Poser scene for their shape only (primitives do fine jobs in most cases, like blocks for buildings)

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As the ‘real’ objects catching the shadows are in the background image, one should avoid having any objects behind (or visible through) those shadow catchers in the Poser scene. That’s why the back wall and ground plane were made invisible in the right image. Otherwise, these will hamper the blending of the render with the background, and catch shadows as well.

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A few of them do, and here they are:

Intermediate

Switching OFF the Subsurface Scattering option (Poser 8 / Poser Pro and up) will disable the nodes

• CustomScatter
• Subsurface Skin

to save render time at testing.

Switching OFF the Raytrace option disables IDL lighting, as well as the nodes from the Lighting > Raytrace group:

• Reflect
• Refract
• Ambient Occlusion
• Gather
• Fresnel

again, to save render time at testing. And, by the way, my lights can’t have raytraced shadows either.

The Raytrace Bounces slider (from 0 to 12) does affect IDL lighting as well as raytracing in reflections and the like. Each surface passed or bounced at, counts for one, so passing a refractive object takes two. Rays gradually die a bit when bouncing, and when the limit as set is met, the ray gets killed anyway. This mainly affects internal reflections when reflectivity is combined with transparency.

Reflection

Reducing Raytrace Bounces might result in pixels in the render which won’t receive a ray of light, and remain dark. Or at least the reflection of the object is discontinued somewhat. In other words: incomplete spots in the render, artefacts. The higher the slider is set, the less is the risk that those occur. And when the rays only need a few bounces anyway, then a high value won’t make a difference and no killing takes place. The slider sets a max value.

Reflect, max 1 ray, each ball reflects the other but not its surface color which is made by reflections.:

Reflect, max 2 rays, each ball can reflect the others surface but not its own reflection in that:

Reflect, max 4 rays, and render times are hardly prolonged:

The spots missing reflections are black because that’s the color set as Background in the Reflect node. I can use any other color, or white with an image attached.

In that case, the Raytrace Bounces slider mixes raytraced and image mapped reflections: for the first (so many) bounces the reflection is raytraced, and from then on it’s mapped.

However, increased slider settings hardly increase render times, reflection is an efficient process. This however might change drastically when transparency is introduced as well. Then light not only reflects from the front, but also passes through the object to reflect from the (inside of the) backside of the object. And that ray will get reflected from the inside of the front side, and so transparency combined with reflection makes the infinite reflections of reflections of … etcetera that slows down rendering to its extremes.

Refraction

First, we’ve got Transparency, which is able to let light pass through a surface. Rays from direct light as well as from objects in the scene. And it does so without raytracing, so it’s not affected at all by any Raytrace Bounces value.  But it can’t bend light rays either.

Instead of – or on top of – transparency, Refraction makes light rays bend as well when passing through a surface. And that’s raytracing. But like Reflection, Poser Refraction deals with objects only and does not handle direct light itself. Without transparency, refraction will treat the surface as perfectly transparent for objects and applies bending as required.

So when objects are placed relative to each other to require refraction of refraction of … in the scene, and the Raytrace Bounces value is reduced, the light stops passing through the surface and might cause artefacts similar to Reflection. It depends on the amount of objects, each of them requires two bounces to let the light pass through, but two objects parallel to each other do not generate an infinite amount of mutual refractions like they can do with reflection. Hence, the Raytrace Bounces value does not need such high values anyway.

The number set is a maximum value, when Poser does not need them it won’t use them, but if the number of bounces for a light ray exceeds this limit, the light ray is killed. This might speed up the rendering while it also might introduce artifacts (black spots) in the result. The tradeoff is mine, but as nature has an infinite number of bounces, the max value is the best when I can afford it.

Left: Raytrace bounces set to 4, while 4 objects require 8 bounces. Right: When the value is increased to 8 or more, all objects and surfaces can be passed.

And like reflection, refraction as such is quite an efficient process. Until transparency kicks in.

Indirect Lighting

To some extent, InDirect Lighting (IDL) is an application of reflection. Light hitting objects is diffused back into the scene, hitting other objects and so on. At each bounce the ray dies a bit, and after so many bounces it gets killed if it happens to be still around anyway. In open scenes a ray might get lost into open space, but most scenes applying IDL are encapsulated within a dome. Then killing rays really reduces the amount of rays around, and hence reduce the lighting level.

Some scenes do present dark spots under IDL lighting, especially in the corners where walls and ceilings meet. That’s understandable: rays are bouncing around and one needs some luck to get a ray just in such a corner, instead of just bouncing away from the sides near to it. In such cases, killing rays early by a low Raytrace Bounces setting will increase the risk of missing a corner, and the corners will turn dark and splotchy. So an increased Raytrace Bounces value will reduce those artefacts, as it reduces artefacts in reflection itself.

Note that launching the render via the Scripts > partners > Dimension3D > Render Firefly menu gives me the opportunity to discriminate between raytrace and IDL bounce limits. So I can increase the latter without having the burden of large values for the first.

When I’ve also got direct lights in the scene (like a photographer uses a flash when working outdoors in the sun), this increase in IDL lighting levels will change the balance between direct and indirect light, and I might want to correct for that by altering the lighting levels at the sources of it.

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Mainly for industrial purposes, the response of light by metals is measured in detail, and published in handbooks, Wikipedia, and the like. Graphs basically look like:

Take Copper for instance. About 37% reflectivity in the blues, 47% in green and up to 80 to 85% in the reds. That might read as RGB = (82% , 47%, 37%) or Hue 14° (out of 360) Saturation 55% Brightness 82%. Taking the previous article in mind, I can use that color and leave value at 100%. Or I can increase the color to 100% brightness (RGB = 255,147,115 or 100%, 57%, 45%) and use the 82% reflectivity for Value. The first approach is preferred, and looks like .

Anyway, I also can see in the Graph that Gold compared to Copper is a far better reflector in the greens and yellows, and even worse in blue. That makes gold less red, more yellow, and a better overall reflector. Adding Silver for an alloy, a common practice, makes the gold even more reflective and more light-yellow. Silver itself is a very strong reflector in all colors and therefore will show White, while Tin will be slightly less reflective, and will have a very mild greenish taint over it.

The graph above is quite clear in its interpretation, but I might run into images like

It’s the same story, but showing light response for a much wider color spectrum. Visible blue matches 400 nano-meter = 0.4 micro-meter while the graph starts at 0.2. And visible red matches 700nm = 0.7µm while the graph makes it till even 1.2, infra-red heat, well reflected by all metals as we know.

And the graph adds aluminum, which as I can see reflects slightly stronger in the blues than in the reds giving it a mild bluish taint.

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Or: what do I have to put into the Reflection Value field (Advanced interface)? Or: with what factor do I have to dim (multiply) the color I used according to the previous article? The latter is a much recommended approach when applying Gamma Correction (as available in PoserPro, and Poser 10 and up) to the rendering process. In that case, the Value itself should remain 1.0. Merging the reflectivity value into the color swatch is even a necessity when using Alternate_Diffuse instead of Reflection_Color, as Alternate_Diffuse does not offer a Value slot. This approach is recommended when the material definition offers some Transparency as well.

The value I’m looking for is: reflectivity.

On contrast to common expectations, shiny and reflecting materials only bounce a very limited amount of the light received, back towards the camera, into the render. In jargon: reflectivity is low. That expectations are high is understandable:

• Highlights on a surface do stand out. This however is not due to the reflectivity of the surface, but because the lights which are reflected do stand out in their environment themselves. In Poser however, highlights are addressed by specularity, not by reflection.
• Water, car and glass surfaces do appear quite reflective. This is because reflectivity increases enormously with skew angles, and that’s the usual way we see the environment reflected on those objects (Fresnel effect).

A plain, straightforward, perpendicular reflection, enabling me to see my own face reflected by the surface, is only strong in metals, and mirrors since these are coated with a metallic layer at the backside. The reflectivity of common materials can be found in the table presented below. The table also mentions the color, if any.

Table of Refraction Index (IoR) and Reflectivity (R)

Material	Refraction index (**)	Reflectivity	Coloring (RGB)	Result (RGB) = Reflectivity*Color
Water	1.33	0.020		5, 5, 5
Sugar solution	1.42	0.030		8, 8, 8
Oily fluids	1.50	0.040		10, 10, 10
Glass	1.50	0.040		10, 10, 10
Heavy Glass	1.60	0.053		13, 13, 13
Impure glass	1.80	0.082		21, 21, 21
Opal	1.45	0.034		9, 9, 9
Quartz	1.50	0.040		10, 10, 10
Salt	1.50	0.040		10, 10, 10
Amber (*)	1.55	0.047	Brown/orange (90.2%, 68.6%, 0%)	12, 12, 12
Onyx, Amethyst	1.55	0.047		12, 12, 12
Pearl	1.60	0.053		13, 13, 13
Aquamarine, Emerald (*)	1.60	0.053	Light Cyan, Green (0%, 66.7%, 45,1%)	13, 13, 13
Turquoise, Tourmaline (*)	1.65	0.060	Dark Cyan (0%, 50%, 50%)	15, 15, 15
Sapphire (*)	1.77	0.077	Dark Red (50%, 0%, 0%)	20, 20, 20
Zirconia	2.15	0.133		34, 34, 34
Diamond	2.40	0.170		43, 43, 43
Lead	2.60	0.200	Bluish Grey (50%, 50%, 62.5%)	41, 41, 51
Titanium	6.15	0.519		132, 132, 132
Tin (Sn)	6.54	0.540		138, 138, 138
Chrome	6.76	0.551		141, 141, 141
Nickel	8.79	0.633		161, 161, 161
Platinum	9.45	0.654		167, 167, 167
Copper	18.78	0.808	Reddish brown (86.3%, 35.3%, 0%)	206, 84, 0
Gold	36.81	0.897	Reddish yellow (100%, 70.6%, 0%)	229, 161, 0
Aluminum	43.43	0.912	Bluish (95%, 95%, 100%)	221, 221, 233
Silver	119.20	0.967		247, 247, 247
Zinc	17.94	0.800		204, 204, 204
Steel	11.25	0.700		178, 178, 178

See http://refractiveindex.info/ for details on all sorts of stuff. See http://colors.findthedata.org/ for colors.

(*) for fluids, glasses and gems the color affects the light passing through. The reflection color however is white, as these ain’t metals.

(**) On Refraction Index. Warning: High School Math stuff ahead.

For all materials, non-transparent ones like metals included, Reflectivity (R) and Refraction Index (IoR) are related:

R = [ (IoR  -1)/(IoR +1) ]²     and/or     IoR = ( 1+ √R) / (1- √R)  (√ for square root)

This too stresses that reflectivity is quite low (less than 10% in most cases) for transparent materials like fluids and glasses, while the Index of Refraction is pretty high (usually 10 and up) for non-transparent metals. It’s this IoR value that has to be used in Fresnel nodes and the like. When you like to have a more detailed understanding, try a physics class on optics for a change. Kidding, it’s complex stuff.

Alloys

Metals are combined, usually for the physical properties of the resulting alloys. These are stronger, more flexible, more durable, less brittle, cheaper, and so on, compared to the pure stuff. For Poser renders, I’m doing quite well when simply using the mixing percentages for the resulting color and reflectivity.

Alloy	Mixture
Yellow Gold (22K)	92% Gold, 5% Silver, 2% Copper 1% Zinc
Red Gold (18K)	75% Gold, 25% Copper
Rose Gold	75% Gold, 22% Copper, 3% Silver
Pink Gold	75% Gold, 20% Copper, 5% Silver
White Gold	75% Gold, 25% Platinum
Soft Green Gold	75% Gold, 25% Silver
Green Gold	75% Gold, 20% Silver, 5% Copper
Purple Gold	80% Gold, 20% Aluminum
Brass	67% Copper 33% Zinc
Bronze	88% Copper 12% Tin
Yellow Copper (Messing)	60% Copper, 40% Zinc
Pewter	90% Tin 10% Lead

For example: when mixing 90% Gold (reflectivity 0.897) and 10% Silver (reflectivity 0.967) then the resulting alloy will have a reflectivity of 90% x 0.897 + 10% x 0.967 = 0.994. And I can do a similar thing to the RGB values of their respective colors.

Making an Easy Life hard

So, I can look up the color and the reflectivity of a metal, a glass or fluid, put these values in the Reflection_Color and Value fields respectively, and I’m done?

Not really, as I have to compensate for double-counting. For instance, the material at hand has no specific reflection color but does have a 70% reflectivity. Then I can either put in White for Color and 70% for Value, or I put in 70% Grey for Color and 100% for Value. But I should not combine 70% Grey in Color with 70% in Value, as that will reduce the surface reflections to 70% x 70% = 49% instead. This especially requires some care when a color is applied indeed. When that color has 90% brightness, then the first step in reduced reflectivity is already taken care of. Applying a reflectivity value of 80% as well will reduce the surface reflections to 90% x 80% = 72%. Vice versa, when I want that say 70% overall, then I should enter the appropriate 90%/70% = 80% in the Value field.

The recommended approach however is to reduce the brightness of the color swatch, and leave the Value at 1.0. Or even better, plugin any reflection node into Alternate Diffuse instead of Reflection_Color. See this article for details on both.

Okay, so I’ve got a color like RGB = (50%, 50%, 62.5%) or as Poser says: (127, 127, 159) and I want to turn it into its 100% brightness equivalent. How should I do that?

• Take the largest number, which is 62,5% or 159 for Blue in the example
• Divide all RGB values by that number, and multiply by 100% or 255 respectively In the example, that would make 50/62,5*100% => 80% , 80%, 100% or 127/159*255 => 204, 204, 255.
• Now, the Value field can get its proper Reflectivity, or the color swatch can get dimmed to the proper result. A 20% reflectivity will then result in 16%,16%,20% or 41,41,51.

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Or: what do I have to put into the Reflection Color swatch? For short: white, except for colored metals. Eventually with a reduced brightness for reflectivity, which is a much recommended approach when applying Gamma Correction (as available in PoserPro, and Poser 10 and up) to the rendering process. Merging the reflectivity value into the color swatch is even a necessity when using Alternate_Diffuse instead of Reflection_Color, as Alternate_Diffuse does not offer a Value slot. This approach is recommended when the material definition offers some Transparency as well.

On about all sorts or materials, reflecting surfaces are neutral, as having a blank lacquer on top of it. The incoming light bounces directly from the surface without entering it at all, and it’s from within the surface that objects get their color. Reflections do not filter the color, and hence are best represented by some shade of gray (white for 100% reflection).

This however is not the case for metals. For those materials, light does not enter the surface (so formally metals don’t have diffusion) but some colors bounce more effectively than others. Gold bounces best in the yellow/red range and less efficient in the blues, copper bounces best in the deeper reds, while more bluish metals bounce better in the blues than they do in the reds. See the next article for details on colors of metals and alloys, and the next after that for a detailed discussion.

In a simple Poser setup, one can choose to color the reflections directly.

Intermediate

In a more complex setup, like a colorful object with dents and rusty spots, one would have to put a (perhaps even modified) copy of the diffuse channel into the reflection channel in the material definition to filter the reflections. That’s pretty tedious for a large Diffuse node tree. So Poser supports this by providing the Reflection Kd Mult option (called Multiply with Object Color in the Simple interface) which forces the reflection to be multiplied by whatever results from Diffuse Color. This option is OFF by default and is intended to be switched ON for metals, and for metallic materials like some car paints.

Option ON

Reflection applies the Object (Diffuse) color using the Multiply option. The Reflection Color itself should remain white to avoid double filtering. In this case, even metals should have a Diffuse color too!
 or

Option OFF

Now Reflection has a color of its own, for metals that is.

Formally, metals have a high reflectivity and no diffuse. Ensure that there is always something to reflect, then, using Raytrace (above) or an image (below). As there is no Diffuse, do not multiply with it!

or

In all cases above, note that Reflection deals with objects in the scene only. So I have to set up Highlight / Specularity in such a way that this ‘reflection of direct lights’ is handled similar to the other reflections. Metals color, non-metals don’t, as a guideline.

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Light from any direction hits a surface, penetrates it for a very slight amount – which will give some absorption, and then it gets re-radiated in a color-filtered way equally in all directions. The path back to the surface will give absorption too, proportional to the distance D traveled through the object surface.

As this distance D is inversely proportional to the cosine of the exiting angle (D=D₀/cos(a)), the intensity of the diffuse light in that direction will be proportional: I = I₀ cos(a). This is the angular distribution of outgoing, diffuse light, according to the mathematician J.H. Lambert (about 1750). At perpendicular scattering, angle a=0 so cos(a)=1 and the response is maximal, while at parallel scattering cos(a)=0 and there is no response at all.

And since cosine calculations are hardwired into modern CPU electronics, this is a speedy rendering approach by any means. Therefore, Poser includes Lambert shading into Diffuse (see the basic and intermediate articles on this). This offers a resource-friendly first step towards more realistically looking renders. And, for people who want more steps in that direction, Poser offers alternatives like Clay.

Now, look what will happen to the render result. A specific area on the render plane (say: a pixel), marked green in the illustration, gets its light from an area on the object surface (marked green as well). At skewer angles a between surface normal and camera, this area on the object gets larger: A = A₀ / cos(a).

At skewer angles such an area emits less light per unit of surface (cm² or alike) and the resulting amount of light onto the pixel in the render plane is I * A = I₀ cos(a) * A₀ / cos(a) = I₀ * A₀ is a constant

So the Lambert shading not only matches a nice explanation on diffuse lighting, it also makes that the intensity of light in the render result does not depend on the camera angle to the surface. Because at skewer angles the pixel in the render represents a larger area on the object surface, which diffuses less light towards the camera, and both effects cancel out.

Look at the light

This leaves the effect of the incoming light itself. At skewer angles, the same amount of light will hit larger and larger areas of the object surface, so the intensity per unit of surface decreases accordingly: L = L₀ cos(b) . Besides the math, this means that the extent to which shading reveals the shape of an object, depends on the ‘directivity’ of the light only. Point lights are quite directive, even a flat surface it lit under varying angles. An infinite light is less directional, a flat surface is evenly lit but a ball is not. IDL lighting is hardly directive at all, the light comes from all directions and all surface areas are equally lit whatever the shape of the object. Hence the shape of objects is less revealed, and objects will look flat.

Left: point light nearby, the edges get darker faster. Mid: Infinite light. Right: IDL, the ball looks like a disk.

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Nodes are the essential building blocks in the Advanced interface to the Poser Material Room. They are the graphical representation of mathematical function calls, that is: calculation procedures which turn parameters (inputs) to a result (output).

Intermediate

In a mathematical way (rendering is all about endless computations, isn’t it) the PoserSurface definition can be read as

PoserSurface =

 (Diffuse + Alternate_Diffuse) * (1-Transparency) +
(Specular + Alternate_Specular) +
(Ambient + Translucence) +
Reflection + Refraction

while Bump and Displacement act as special modifiers (and Transparency does have various side effects when reflection and refraction are applying raytracing).

A component of the PoserSurface can be read as

Diffuse =

(Diffuse_Color * DiffuseColor-input) *
(Diffuse_Value * DiffuseValue-input)

where each “input” refers to the result of any kind of node having its output connected to it. When there is no node attached, the input acts as a 1.0, or: neutral in the multiplication.

Each node offers one output which can be connected to (serve as input for) one or more (!) input connectors. Each input connector can have at most one output connected to it. If I want a combination of nodes attached to an input socket, I need a construction node to define the combining math myself.

As the example above reveals, a node (like Image_Map) offers inputs or parameters of various nature. Some of them are ‘autonomous’, like the Image_source involved or the Auto-fit option. These cannot be driven by other nodes any more. But other inputs, like U_Scale, can offer a dial-value filtering of any additional results from other nodes connected to it.

Thus far, all node inputs and outputs are visible in the interface, and can be addressed explicitly. But be aware that a lot of nodes also have some additional interactions with the Poser scene or system.

• The root node, PoserSurface, looks like a regular node with inputs but its output slot is “missing”. It sends its results to the renderer instead.
• Actually, things work the other way around: for each surface element the renderer needs some results for, the PoserSurface function is called for that surface-material definition. And that function calls the other functions according to the nodes attached to its inputs, which may call functions according to the nodes attached to their inputs and so on. In other words: PoserSurface is not pushing results into the renderer but the renderer is pulling results from PoserSurface. Complex node trees then make large stacks of function calls, and the calls are made for each surface element in the rendering process. High numbers for pixel samples and/or low values for shading rate in the Render Settings increase the number of evaluations in the renderer, and hence the amount of PoserSurface calls as well.
  
• From all that, the coordinates of that surface spot, in space and time, are available to all node-functions called. U,V,W with respect to the surface, X,Y,Z with respect to scene space, Framenumber with respect to time, and some more as referred to in the Variables nodes group:
  
• Next to the ‘backdoor’ communications with renderer and scene place and time, the nodes are communicating with the lights.

o   The ones in the Lighting > Diffuse group (diffuse, clay, …) require any diffuse lighting from direct or indirect sources to produce their result. No such lighting, no output (0, black, …).

o   The ones in the Lighting > Specular group (specular, Blinn, …) require any specular light, and I need a direct infinite, point- or spotlight to produce that. No specular light on that spot on the surface, then no output. IBL lamps and any light from objects (IDL, ambient, reflection, …) are considered diffuse, even highlights from object surfaces produce diffuse light under IDL conditions and are not considered specular themselves.

o   The ones in the Lighting > Special group (skin, velvet, …) serve both purposes, they offer a response to diffuse light as well as to specular light, and even can combine that with some autonomous ambient effect. Some of them require the Subsurface scattering option in Render Settings to be switched on in order to produce any output at all.

o   The ones in the Lighting > Raytrace group (reflect, refract, …) require light from surrounding objects, and do not work on the light from direct sources. When there are no such objects in front (reflect) or behind (refract) the surface at hand, they can’t do their job and will produce their default ‘background’ response.

For example,

• I’ve got an object which has some response to diffuse or specular light, and produces an ambient glow too. And I’ve got no lights at all in the scene. Then only the ambient glow will show, as the Diffuse and Specular components have nothing to respond to, and the Reflection and Refraction lack any surrounding objects to work with.
• Now I connect the diffuse node to the Ambient_Color slot in an attempt to get some intensity distribution into the glow. What do I get? It kills the glow. The diffuse node will not receive any diffuse light from any source, therefore it produces a null response, which is input to Ambient_Color which will therefore produce black as well.
• So… nodes like those require light onto the surface and produce a response from that, they are not producing light distributions as such for output. No light, null response, black output.

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In a previous article it is discussed that the various components of the PoserSurface definition are simply added up on a color by color basis to make the final result. This topic is on the individual elements of such a component.

In the Simple interface, I can have an image map combined with a color swatch. The color swatch acts like a filter, as if I’m looking at the image through a transparent, colored piece of plastic.

In technical terms, both are multiplied. For instance, take a red swatch, or: RGB=(100%,0%,0%) multiplied with any color (red, green, blue) on a color-by-color basis. That will give: (100% red, 0% green, 0% blue) of just (red, 0,0). The red filter will only let the red color pass through, and will kill the other color parts. That’s why multiplication means: filtering.

Intermediate

The Advanced interface to Material Room offers Value slots next to Color ones, and more nodes to plug into the slots than just image-map.

When a tree of nodes, from either no node at all to a whole complex of combinations, is plugged into the color swatch, then the result from the node-tree and the swatch are multiplied on a color-basis. Red times red (both in percentages, 90% x 80% = 72%), green times green and blue times blue. When a value is supplied by the node chain, then that value is used in all three color channels instead. When no node is attached to the color swatch, then just the color swatch itself results from the transaction or: a node-value of 1 is used.

When a tree of nodes, from either no node at all to a whole complex of combinations, is attached to the value plug, then the result from the node-tree and the plug are multiplied on a value-basis. Both in percentages, 90% x 80% = 72%. When no node is attached, then just the plug value itself results from the transaction or: a node-value of 1 is used. When the node tree offers a color instead, then this color is turned into a brightness value first.

Then, the resulting value is multiplied to the resulting color, for red, green and blue separately.

Example:

Image with brightness and color variation plugged into Diffuse Color, and different image with brightness and color contrast plugged into Diffuse Value. It’s like stacking filter on filter on filter …

And for now… something different

Technically, various components offer a filtered access into the spine of the PoserSurface material definition. Whatever I plug in, it gets filtered (aka multiplied) by the Color and Value present. The Color will be affected by Gamma Correction, the Value will not. So 80% White and 100% Value will behave different from 100% White and 80% Value under GC render conditions. See this article for details.

This holds for Ambient and Translucence, and for Reflection and Refraction. Diffuse and Specular are similar, but include a build-in shader as well which manages the distribution of light intensities over the surface. See the basic and intermediate articles on Diffuse, the basic and intermediate articles on Specular, and the article on the Lambert shading itself. Alternate_Diffuse and _Specular in turn offer the color swatch (filtering) only. Bump and Displacement are different, they act as special surface modifiers.

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The various portions of a material definition all add up to the surface response to the lighting in the scene. In order to present a realistic look – to any extend – one has to balance the contributions of those portions to each other, and to the various kinds of lighting in the scene. See the short answer and an  elaboration on this.

Intermediate

Next to that, all those portions of a material definition just add up mathematically, on a per-color basis. So RGB (80%, 60%, 15%) + RGB (60%, 50%, 10%) = (140%, 110%, 25%). This may cause overlighting (any value >100%) from

= Diffuse * all direct and indirect diffuse lighting + Specular * all (direct) specular lighting + Reflection * all light from other objects in the scene + Ambient + Translucence (both representing glow from the object itself)

I can dim the light (which will make the ambient glow look stronger) or I can dim all material aspects proportionally. This latter will darken the image (which can be corrected for in post, using Photoshop or GIMP or alike) but at least will avoid the clipping effects. Note that applying Gamma Correction (GC) automagically caters for some darkening, overlight reduction and re-brightening and should be used when possible. GC is available from Poser 10 on, and from Poser Pro 2010 on.

For instance, assuming all colors to be white so we’ve got to consider intensities and brightnesses only, say a light producing 90% diffuse and 80% specular light shines on an object having

• 80% diffuse
• 20% specular
• 20% ambient

This will produce 90% x 80% = 72% in the diffuse channel, plus 80% x 20% = 16% in the specular channel, plus 20% in the ambient channel, equals 72 + 16 + 20 = 108% which will get clipped down to 100% when presenting the result.

But do note

• That addressing diffuse and specular lighting separately requires the Advanced interface to the material room, using the color swatches for both
• Setting the intensities for Diffuse, Specular and Ambient can be done via the Simple interface, as well as via the Advanced interface, using the appropriate color swatches
• All color swatches for light and material will get affected by the Gamma Correction (GC) mechanism while rendering, which reduces the overlighting effect by itself. GC is available in Poser from version 10 up, and in Poser Pro from version 2010 and up. See further articles on its use, and on details.
• Setting the intensities for Diffuse, Specular and Ambient can be done via the Advanced interface, using the appropriate value dials. These are not affected by the GC mechanism, and hence will produce a different result from dimming the color swatches.

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The short answer is NO, and be advised that there are a lot of contrasting opinions in the forums and around on the Internet. Some opinions are presented as religion, and their advocates act as true evangelists. Others are more relaxed. What does it matter?

Well, 3D programs like Poser are very feature rich, and far from easy to comprehend fully (at least to me). And finally, I need a “way of thinking” to use those programs effectively and efficiently. That is: for establishing a specific effect in my result, I want to get a good way to accomplish that, without wasting a lot of time (and other resources) on thinking it up, implementing it, testing, fine-tuning and rendering. The best “way of thinking” for me depends on my background (experience, interests, education, expertise) and the kind of effect and result I want to accomplish. Stylish results for comics have different requirements from studies for oil-painting or crayon-drawing, from product-casing, from animation or from photoreal’ish rendering, either for web-galleries or for large scale fine print.

So in some cases the “let’s not add up to 100%” approach is good enough, in other cases people might prefer a complete Master of Physics approach, or anything in between. It’s good to have all those variants around, and to add some of them to a personal toolbox.

More in detail

Various opinions arise from the limitations on materials in nature, when a single source of light hits a surface. That light can be reflected, diffused, transmitted and so on, and hence these portions should not add up to a value larger than one (100%). It could be less, to represent absorption in the material. However, the various portions of a Poser material respond to quite different – and quite independent – sources of light. This is presented in a basic way. And there are various practical considerations to be taken into account.

Intermediate

For a better understanding, let’s review the situation for direct lighting and for indirect lighting separately. In both cases, Bump and Displacement, as well as Transparency and Refraction will only affect the distribution (and eventual reduction) of light re-emitted by the object towards the camera into the render, but will certainly not increase the amount of it. So these aspects can be ignored for the moment.

For the sake of simplicity, let’s first consider a single (direct, point) source lighting an object in the midst of a scene, under non-IDL conditions:

Direct Lighting only

The diffuse portion of the light will be re-emitted by the Diffuse portion of the material, while the specular portion of the light will be re-emitted by the Specular part of the material, emulating the reflection of the direct light source (the lamp) itself. The Reflection part of the material will bounce the diffuse and specular results from the light source via other objects in the scene onto the object surface (unless a reflection-map is used to fake the effect).

Red: direct diffuse light into scene and onto object, resulting in general visibility Green: direct specular light into scene and onto object, resulting in highlights= reflection of lamp Blue: visibility and highlights combined from the scene reflected onto object = reflection of scene

Note again: the reflective surface of the reflecting object not only does not reflect the direct light source itself (as a lamp is not considered an object at all), it does not reflect the light rays either. So I cannot use a flashlight and a mirror to illuminate an object around the corner.

Since Reflection and Specular both represent the same reflective properties of the material for just different sources of light, they should be balanced somewhat for the objects surface. This effectively means I’m balancing the visibility of the lamp with the visibility of the scene objects, both onto the surface of the object at hand. And – for that same object surface – I’ll have to balance its Reflection / Specular at one hand to its Diffuse at the other hand, to make a neat impression of the objects reflectivity as such, despite the fact that the sources of the lighting are different.

On top of this, the material can offer some glow of its own, in the Ambient or Translucence channel (*). This will wash out some surface details of the object, and will just add to the light re-emitted from the surface by Diffuse, Specular and Reflection.

InDirect Lighting conditions

Second, let’s switch on IDL conditions. Now all the light (diffuse, specular, reflections, ambient glow, etc.) re-emitted by any object in the scene works as a diffuse light onto the object (and all other objects) as well, in addition to the already available direct lighting. Effectively, this will turn up the diffuse lighting level seriously. Not only will this turn my render into an overlit one unless I lose a few lights and turn down the intensities of others, it will also distort the balances between the material portions sensitive to direct light (Diffuse, Reflection), and the portions which are not (Specular, Ambient).

For Specular, this implies that we either have to re-balance this property against Reflection and Diffuse, or we have to rebalance the specular properties of the available direct lights against the new IDL-based lighting level. The latter part might take far less effort, especially in material-rich and/or crowded scenes.

To complete our understanding on Reflection, let’s re-consider the use of a flashlight, shining on a mirror in an attempt to illuminate an object ‘around the corner’. The (direct) flashlight will produce a bright spot from diffuse and specular on the mirrors surface. Under IDL conditions, this spot will act as a diffuse light source, shining all around creating some extra illumination ‘around the corner’. There still will be no defined bundle, though.

For Ambient/Translucency (*), the hotspots (led-lights or so) on the object might need to glow a bit more to be seen within the altered IDL lighting level.

(*) Ambient and Translucence are equivalent parts in the material definition. Just use either one or the other. The main difference is that Ambient is supported by the Simple interface, and by most exports to non-Poser file formats and renderers, while Translucence is not.

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