like does it scatter the bounces a bit?  

(PP12)

Hmmm... That's a bagginsbill question, but I'd say it probably doesn't. It's only simulating the shading on the object it is on. Displacement, however, will, I imagine, since it simulates "real" geometry. I'm not completely sure, in either case, though. But, that seems logical. (Both me being unsure and my assumptions mentioned here. :) )

lol, thanks.  

i saw the phenomena in carrara.  

want to test in poser and ds, but the dayjob is keeping me busy. 

coulda been cause the bump map was color. didn't test that.

i've seen renders with the character's face shadow shmootzed.
misfired shadows from transmapped bump mapped hair and bump maps in the skin shader?

Theoretically, Morkonan has it right.  That is how it "should" work.  bump no effect, displacement yes.  Let us know how it turns out.

Are you using AO or some kind of indirect light? Usually, without seeing an image, the best I can get is usually :), if you are getting smootzing, it is due to not enough samples for creating shadows or determining light calculations. 

 Hi,

i dont really understand the question, but just an example

bump, displacement and gradient, same shader  

As Anthanasius points out, we all know bump does not create a new shape on the shadow of something.

But - it can produce character's face shadow shmootzed as MLP mentioned.

Remember, bump alters the normals. If it alters them so far that the virtual surface points AWAY from your light source, it turns darker.  Perhaps it even goes black, if the only arriving light is now on the "wrong" side of the normal. This is not a shadow (light is blocked) but rather the ordinary thinning of the light coming at a shallow angle.

(Imagine spraying a water hose straight down at the ground - you pound a tiny area with all the molecules - 100% of the water hits a few square inches. Now shoot the water out mostly horizontally - the molecules spread out and the density of the water falling on any given square inch of ground is way lower. None of the water is "blocked" or "shadowed" - all of it does hit the ground. The same happens with photons. )

Also, when Poser "thinks" its way around the virtually displaced surfaces (i.e. interpolating normals), it can get upset if the bumped surfaces virtually "cross over" each other. In such cases, you get total blackness. I have demonstrated this long ago when trying (endlessly!) to teach people how to use bump maps correctly in Poser, which does NOT think that gray (.5) is neutral. Black (0) is neutral - end of discussion.

Click here for a thread on this topic

The thread discusses bump artifacts that cause lighting issues.

hi all,

just bumping in on this as I do have a deviant opinion, from the image below. It shows four standard boxes under default lighting, each box is 0.1 PNU (10.2" or 26.2cm) in size.
The colored one at the back is for illustration only, it has a simple tiled pattern assigned to its Bump as well as Diffuse channel so I can see what's dark and what's bright. The gray mortar is a bit brightened up, so it makes about 50% under Gamma Correction.

The boxes at the front are put closely to each other, the left one does not have any bump, the middle one has a very stong bump: 2,62 mtr (thats 10x the box size!) while the right one is still quite bumpy: 0,262 (thats 1x the box size). My units are meters. 

What do I see:

• both the strong bump effects show equal effects
• all bump effect gets completely lost when a box boundary is crossed. Especially from the middle to the left box there is no clue whether a surface on the middle box is raised, indended or 'neutral'.

My conclusions:

• the bump effect is a fake one, making a surface element look raised or lowered relative to a neighboring surface element, depending on the relative (!) brightnesses within the same bump map.
• the fake effect is limited. One can have it 10% fake, or 50% fake, but there is some 100% fake level which cannot be exceeded. Higher values do not make stronger bump effects. 
• the bump effect is limited to surface elements addressed by the same bump map. It does not make elements look raised or indended relative to elements addressed by another map.
• in other words: their is just no such thing as neutral. As the boundary between the left and middel box makes clear: white, gray and black are equally neutral, they have only meaning relative to each other within the same mapped area. 
• the story on distorted normals is a nice one, but not explaining why I don't see distortions on the box boundaries. So, to me at the moment, I'm not buying, and bump is just a fake shadowing / highlighting effect. Nice, but fake.

• on top of all this, do remind that GC, IDL as well as SSS all reduce the highlight / shadow contrasts, and hence tend to reduce the effects of bump (and displacement, and overall image depth, etc).

 That's my opinion on bump.

what's the best type for making eyebrows standup from the skin?  
bump, normals, displacement?

thanks.

in my opinion: the closer the shot, the more detail you need. So bumps (*) are fine for distant shots, displacements do well for intermediate shots, and for close-ups one needs the hair room ( this might give you a start on that).

(*) normals are sort of low-quality bumps, aimed at high-speed (30fps) game-rendering. They are available in Poser so you can use figures from a gaiming environment in your scenes while those figures offer no bumps or displacements in their materials but offer normals instead. I never use them when there is an alternative. We did plenty of threads about that. 

if i had to pick a favie, i like black as the neutral bump color.
but then, what color would be negative to black?

coming to the revalation nuthing in my runtime is render ready.  woes

i dunno, if anyone interested, this is the test render put me in seek mode for bump tutelage. 

just read my earlier post, there is no such thing as a neutral color for bump.

When two (neighboring) surface elements A en B are addressed by the same bump map, and A has a darker shade in the map compared to B, then A will look indended, lowered, compared to B. And when the bumpmap for B is black, no surface element will appear lower.

For the tiling floor, my suggestion is not to put shine on the mortar between the tiles. Use a map for surpressing the reflectivity. 

[quote]i dunno, if anyone interested, this is the test render put me in seek mode for bump tutelage. [/quote]

Generally speaking, any 'effect' that is calculated based on normals of a surface is affected by bump mapping. This includes reflection (like in your render) lighting, refraction and edge falloff / fresnel. Also generally grey is indeed the 'neutral' in most renderers cause it allows you to have both height (white) and depth (black) in the same bump map but I dunno why it's not like that in Poser. Maybe they wanted to keep it compatible with displacement ?

just read my earlier post, there is no such thing as a neutral color for bump.

When two (neighboring) surface elements A en B are addressed by the same bump map, and A has a darker shade in the map compared to B, then A will look indended, lowered, compared to B. And when the bumpmap for B is black, no surface element will appear lower.

For the tiling floor, my suggestion is not to put shine on the mortar between the tiles. Use a map for surpressing the reflectivity. 

thanks, though, but this is confusing information to me.  earlier post doesn't make sense to me, either 

"but then, what color would be negative to black?"

First of all, bump (height) data are numbers, not colors. When we use an image map to perform bump "mapping" the image is used as numbers. The numbers in an image are actually there but we visualize them as colors. They're not - they're numbers.

[ This is why it is super important to make sure you don't apply any gamma but 1.0 to the image - the image is not a picture with colors for your computer monitor. It is data and is to be interpreted with a gamma of 1. ]

Your question was not phrased correctly. What is negative to 0? The answer is: negative numbers, of course.

We've acknowledge that the number 128 (of 0 to 255) is considered neutral in many apps. Notice that all the numbers are positive: 0, 1, 2, 3, 4, 5 ... 253, 254, 255. In an 8-bit PNG or JPG or BMP those are the only numbers it can make. So how would a negative bump or displacement be represented?

It's because the number isn't taken STRAIGHT out of the image - it's further processed. 

First, all apps divide it by 255 to get a number in the range 0.0 (0/255) to 1.0 (255/255). The value 128 becomes approximately .502 (128/255). It's close enough to call it .5 for most purposes.

Then they subtract .5 from the map numbers. This means 

128 becomes (128/255 - .5) = approximately 0 <<< Neutral - no movement of the surface from its original position

0 becomes (0/255 - .5) = approximately MINUS .5 <<< A negative movement of the surface equal to half the total peak-to-valley distance chosen by the user.

255 becomes (255/255 - .5) = approximately .5 <<< A positive movement of the surface equal to half the total peak-to-valley distance chosen by the user.

In Poser it doesn't do that subtraction of .5 - it just does the divide by 255. But we add the subtract .5 with a node and it's the same.

That is how a height map (used for bump or used for displacement) can represent positive and negative movement. 

Following those steps, the final multiplier in the bump or displacement parameter value is multiplied with what you plugged in to scale the height to any value you want. But no matter how you scale it or offset it, there are only 256 heights possible when you feed it an 8-bit image, because there are only 256 numbers possible in 8 bits.

You can use the same height map to perform either bump or displacement. Which you choose to do depends on what tradeoffs you'll make, and how good the renderer is.

Poser is not good at making large movements with displacement - often the mesh seems to be tearing at polygon boundaries. For example, asking it to simulate moving a surface 10 meters is asking it to fuck up.

For small height movement, we often cannot tell if the surface has actually moved or not. Our visual cue comes almost entirely from the angles produced, rather than from the positions produced. Therefore, even if the surface remains entirely flat with bump mapping, the visual cue is very similar to what we perceive when the surface is actually moved. This means that bump is good enough for most small excursions. Since bump is faster, takes less memory, and does not tear, we prefer bump for small height changes.

I have used displacement for eyebrows once or twice - in a closeup, the connection between the raised hair and the skin looks stupid. From a distance it looks ok but not much different from bump mapping. So I feel that the answer to "what is best for eyebrows", is real hairs. If you can't do real hairs, then bump.

A corollary question is, in Poser, is it possible to work with negative colors? (What I have called hypocolors in the past.) The answer is yes. Poser is not one of those renderers (such as LuxRender) that refuses to store negative numbers in a color variable.

However - if you ask what does a negative color look like, then the answer is it looks the same as black.

The difference appears when you don't LOOK at the color, but instead you use it in color math - then the negativeness is revealed, even though you have no direct way of looking at it.

(Kind of like electromagnetic waves. You can't see them - but that proves nothing at all. They exist and it's part of how light works.)

thanks.  i'm conscious of intersecting bumps now, along inner edges.

lucky they didn't try to divide by zero, eh? lol