In poser pro, gamma correction is use on the texture map, and the gamma correction Wacro made by banth (http://www.renderosity.com/mod/forumpro/showthread.php?message_id=3463464&ebot_calc_page#message_3463464), the GC is add on the shader, so are there any different ?:m_confused2:

Bantha made a macro for people who do not have poser pro. You should not use it if you have Poser Pro.

thanks bagginsbill : )

IOW, you should not use Bantha's wacro if you are using Poser Pro and rendering using the inbuilt gamma correction in Firefly (set up in your render settings).

ETA: to explain why I said what might seem obvious: I use Poser Pro and material gamma correction shaders instead of the inbuilt Firefly gamma correction.

If you have poser pro, why would you do that ?

Robyn had built an extensive collection of material based gamma correction shaders before PP emerged.  Rather than go back and reset everything, she turns Gc off in the render settings.

Quote - I use Poser Pro and material gamma correction shaders instead of the inbuilt Firefly gamma correction.

really? so are the result the same or different? 

RV says they are different. I think they are nearly identical, but I know that others do not necessarily take into account all of the GC system. For example, if you use a light that is not set to white in the light color, then that color is anti gamma corrected by render GC, since it is non linear. If one were to only deal with shader GC, it would be easy to not remember that a light has a shader as well. The outcome will be different if that detail is ignored. So, if you are using shader GC, but you are being selective about its application (whether intentional or accidental) then a difference will become apparent. If you succeed in getting all the math right, then the outcome is nearly identical. Exceptions include objects with partial transparency, since there is no shader GC technique allowing us to deal with that identically. In such cases, render GC is more accurate. Other very subtle differences have to do with mip mapping and anti aliasing, but these are truly marginal differences, largely of interest only to purists. The big difference where shader GC just fails is when you use global illumination (IDL). With that, the shader becomes part of the lighting equation, and gamma corrected colors throw that off. With Poser Pro 2012 there is also subsurface scattering which is difficult to use right with shader GC. If realism is the goal, then you will want SSS and IDL, and render GC will give correct results more easily.

That would be one reason - but the bigger reason, one I can't explain the reason for, HBorre - is that my makeup shaders don't behave right with the renderer GC... but work fine with the material based GC. Yes, I've made the gamma correction 1 for all non-colour maps, but what happens is the colours aren't anywhere near as saturated, so I have to turn the values up. I'll show you what I mean.

Here is Katie, my most recent V4.2 dial-turn girl. The first image is material GC = 2.2 for all colour, as set by Parmatic:

...and this is with material GC set to 1, and Render GC set to 2.2:

All other settings in the shader and the render were left the same. Lighting, everything. All non-colour image GC settings were at 1 for both renders.

Personally I would 'trust' render GC more and try and find what's going wrong in it... Mat GC is pretty much a workaround for people that don't have access to pro, render GC is what you should be basing your work on.

About the desat look, what's the makeup setup like ? I assume you are painting maps in CS3 and layering them onto the base texture in Poser ? If so, have tried doing the layering in photoshop itself (as a test) and then using the new texture directly ?

maybe ya could try it with bill's lite meter.  figure lighting differs from bg to some extent IMVHO.

Quote - Personally I would 'trust' render GC more and try and find what's going wrong in it... Mat GC is pretty much a workaround for people that don't have access to pro, render GC is what you should be basing your work on.

About the desat look, what's the makeup setup like ? I assume you are painting maps in CS3 and layering them onto the base texture in Poser ? If so, have tried doing the layering in photoshop itself (as a test) and then using the new texture directly ?

You appear to know something about the difference between the two. My understanding the difference is considered to be negligible, yet you seem to consider the difference in algorithms significant. What is it?

I didn't say there was a difference in algorithms, I said I wouldn't trust mat GC. Render GC is done by FF itself and that has access to every last part of the render equation. Besides bugs, you should get what you expect. Shader GC though relies on accessing the poser shading system and trying to bypass/supplant it to 'inject' GC in there, which is very much a user hack. Hacks are not a good idea to base ones work on unless you really have no other choice.

eg note that the first render is way too dark in many places (hair, the dress) almost as if you hadn't done any GC at all. The second one looks much more realistic and natural for the amount of lighting you have in the scene IMO. Are you really sure you are getting the correct result in the first one ?

You're absolutely right, ghonma - I used no material GC shader on the hair for first one. Good pick-up. Nor the dress, either... nor the background. The only thing I do have a material GC shader on is the skin. The whole shader plugs into the Alternate_Diffuse channel of PoserSurface. Nothing else. So, unless I understand things incorrectly, with the Alternate_Diffuse you pretty much get what you plug in. And setting GC to 1 for skin and rendering with rendererGC at 2.2 for skin should yield similar results. Or identical, in a perfect world. Unless Poser's Firefly algorithm IS different, which would then yield different results.

So, either there is a difference in algorithms or Firefly doesn't see Alternate_Diffuse as virginal information as I thought it did.

The process is simple to me (I'm a nurse, so things have to be massively simplified):

-Linearise colours

-Process (do maths on, i.e., add, multiply, blend, whatever) colours

-Gamma-correct colours

No? Am I missing something?

Oh, why do you say material GC is a hack? A hack implies an incomplete solution. How is Bagginsbill's GC solution incomplete?

I used 'hack' in the engineering sense, where it means cobbled together or a quick fix solution. Hacks are not incomplete or bad, in fact they are only way to solve things sometimes, but they are not long term solutions. You should only rely on them till there is a better, more documented way.

And i'm not sure whether alt diffuse is working ok or not, I don't know enough about FF's internals to comment on that.

Quote - I used 'hack' in the engineering sense, where it means cobbled together or a quick fix solution. Hacks are not wrong or bad, in fact they are often the only way to solve things sometimes, but they are not long term solutions. You should only rely on them till there is a better, more documented way. And I dunno whether BBs solution is incomplete or not, I don't know enough about how alt diffuse works to comment on that.

I don't have any documentation on Firefly's GC implementation.

I do, however, have Bagginsbill's documentation. It's all over the threads here. And it appears to be remarkably complete. So, based on your criteria for using a solution, I might stick with the "hack'.

Quote - Personally I would 'trust' render GC more and try and find what's going wrong in it...

...which is impossible to do without a full disclosure on how Firefly's render GC works.

Well since you seem to be happy with the results you're getting i'll concede the point. Personally i'd rather stick with a standard approach cause it reduces the number of variable you have to deal with, but that's just my preference.

Quote - RV says they are different. I think they are nearly identical, but I know that others do not necessarily take into account all of the GC system. For example, if you use a light that is not set to white in the light color, then that color is anti gamma corrected by render GC, since it is non linear. If one were to only deal with shader GC, it would be easy to not remember that a light has a shader as well. The outcome will be different if that detail is ignored. So, if you are using shader GC, but you are being selective about its application (whether intentional or accidental) then a difference will become apparent. If you succeed in getting all the math right, then the outcome is nearly identical. Exceptions include objects with partial transparency, since there is no shader GC technique allowing us to deal with that identically. In such cases, render GC is more accurate. Other very subtle differences have to do with mip mapping and anti aliasing, but these are truly marginal differences, largely of interest only to purists. The big difference where shader GC just fails is when you use global illumination (IDL). With that, the shader becomes part of the lighting equation, and gamma corrected colors throw that off. With Poser Pro 2012 there is also subsurface scattering which is difficult to use right with shader GC. If realism is the goal, then you will want SSS and IDL, and render GC will give correct results more easily.

Sorry, missed all that.

So, how does one explain distinctly less saturation of mask-based makeup colours? Into which section of your explanation does this fall?

My guess is you forgot to anti gc a color.

My makeup colours are all linearised before processing and corrected afterwards in the shader... so you must be referring to lights.

I am referring to something that is different, and, by definition, something you are not aware of. if the lights are whiite, then no, not the lights.

As an example of something you may not be aware of, consider the following x = AGC(Blend(a, b, f)) or x = Blend(AGC(a), AGC(b), f) One of these is identical to render GC, the other is not. Under specific circumstances, these two produce the same output, and in other cases produce diffrrent output. Whey they differ, one of them is identical to render gc and the other is not. Can you say which is identical to render GC? Forgive the typos, I am in Edgartown Martha's Vineyard oa sailboat and only have my ipad which is hard to type on.

Assume that a and b are just a color or a color map.

Just to make sure we're singing off the same page, the problem render (as I see it) is the Firefly rendererGC image. To create it, all non-colour maps are set to GC=1 (so, not linearised or corrected, I take it). I don't linearise any colour  - I take it the renderer handles that.

In the material GC render, all colours (except for lights, which are white) are linearised and corrected in the shader.

None of which explains why the colours in the Firefly rendererGC are washed out. Those colours are affected by 1. a blender setting, 2. a mask (which is not colour information) 3. light (something over which i have nil control except to make sure it is pure white).

So, lost.

Sheesh, enjoy your sail, BB... this can wait! There's something sacrosanct about being on the water... iPads and modern technology notwithstanding.

Taking this sick body to bed.... please enjoy the serenity for me.

Quote - As an example of something you may not be aware of, consider the following x = AGC(Blend(a, b, f))

or

x = Blend(AGC(a), AGC(b), f)

One of these is identical to render GC, the other is not. Under specific circumstances, these two produce the same output, and in other cases produce diffrrent output. Whey they differ, one of them is identical to render gc and the other is not. Can you say which is identical to render GC? Forgive the typos, I am in Edgartown Martha's Vineyard oa sailboat and only have my ipad which is hard to type on.

The first equation is identical to render GC ?

x = AGC(Blend(a, b, f))

Which cases will produce different output? 

I'm rarely successful with render GC.  When I turn on render GC, PP2010 gamma corrects everything in the scene.  There isn't a handy GU interface that would allow me to selectively turn GC off for specific Poser objects.  Will PP2012 allow me to turn GC on for background props but leave GC off for foreground characters?

Quote - > Quote - As an example of something you may not be aware of, consider the following x = AGC(Blend(a, b, f))

or

x = Blend(AGC(a), AGC(b), f)

One of these is identical to render GC, the other is not. Under specific circumstances, these two produce the same output, and in other cases produce diffrrent output. Whey they differ, one of them is identical to render gc and the other is not. Can you say which is identical to render GC? Forgive the typos, I am in Edgartown Martha's Vineyard oa sailboat and only have my ipad which is hard to type on.

The first equation is identical to render GC ?

x = AGC(Blend(a, b, f))

Which cases will produce different output? 

I'm rarely successful with render GC.  When I turn on render GC, PP2010 gamma corrects everything in the scene.  There isn't a handy GU interface that would allow me to selectively turn GC off for specific Poser objects.  Will PP2012 allow me to turn GC on for background props but leave GC off for foreground characters?

On second thoughts, if I were a software developer programming GC in Poser Pro, I would anti-GC each color first before blending them.  So, the second equation is identical to render GC.

x = Blend(AGC(a), AGC(b), f))

Is that indeed the problem? Are we linearising/correcting every node in the shader? Even nodes that we don't want this to be happening to? Inquiring minds, etc... :blink:

Quote - Is that indeed the problem? Are we linearising/correcting every node in the shader? Even nodes that we don't want this to be happening to? Inquiring minds, etc... :blink:

In principle you could only do gamma correction for one node: the PoserSurface node. All other nodes, assuming they get linear color input, should work just fine. But because the PoserSurface node has no output you could gamma correct in the material room, you correct it's inputs instead. The assumption "all node inputs are linear", does not hold in some cases, and only in those cases you need to anti gamma-correct(*) anything. This would be the case, for example, with the reflection node which gets its input from other objects in the scene, and because those other objects are gamma corrected, you have to anti gamma correct the output of the reflection node before using this output for other operations.

Apart from those some special nodes that transfer color from one material to another, the most common case for anti gamma correction is more because of your own choice, for example because of whether you use gamma encoded textures or not, or whether you specify the color of those color chips in the nodes by using R,G,B values (from a reflection chart or so) or by using their visual appearance on your monitor. Only you know if these need to be gamma corrected or not.

(*) i am assuming here that "anti gamma correction" is the same as gamma distortion (or gamma decompression), i.e. AGC(x) = x ^ 2.2

Quote - As an example of something you may not be aware of, consider the following x = AGC(Blend(a, b, f)) or

x = Blend(AGC(a), AGC(b), f)

One of these is identical to render GC, the other is not. Under specific circumstances, these two produce the same output, and in other cases produce diffrrent output. Whey they differ, one of them is identical to render gc and the other is not. Can you say which is identical to render GC? Forgive the typos, I am in Edgartown Martha's Vineyard oa sailboat and only have my ipad which is hard to type on.

It looks like the first and second equations will always yield different results base on my simplistic experimentation.  The first equation seems to consistently yield a higher value than the second equation.  If x is the luminance of the object, then the first equation would be identical to render GC since my poser objects tend to look washed out each time I turn on render GC.

In which specific circumstances will the first and second equations yield the same result?

Quote - Is that indeed the problem? Are we linearising/correcting every node in the shader? Even nodes that we don't want this to be happening to? Inquiring minds, etc... :blink:

Good question.  I myself am pretty uncomfortable with render GC since I have no clue how PP2010 gamma corrects my objects and figures when I turn on render GC.  Perhaps bagginsbill can shed some light on this matter for us?

I'm still on the boat and have great difficulty typing.

Quote - > Quote - As an example of something you may not be aware of, consider the following x = AGC(Blend(a, b, f)) or

x = Blend(AGC(a), AGC(b), f)

...

If x is the luminance of the object, then the first equation would be identical to render GC since my poser objects tend to look washed out each time I turn on render GC.

In which specific circumstances will the first and second equations yield the same result?

The second is render GC.

The specific circumstances when they would do the same are when f, the mask or blending value, is strictly black or white, i.e. 0 or 1. Under these conditions, the Blend is actually just a pass through of one the two inputs.

They differ when the blend is a non-zero weighted sum of the two inputs. That is the heart of the rendering equation - summing values from multiple light sources - summing values from specular and diffuse - and this is why linear rendering matters. The linear some is wrong when using gamma corrected values.

Render GC is simple, yet people insist on saying it isn't.

All incoming material (color chips, image maps) are assumed to be chosen on the basis of how they look. Which means they are assumed to be sRGB numbers, not linear luminance numbers. They are gamma corrected numbers.

Since they are assumed to be gamma corrected, all incoming numbers must be linearized. Thus, they are anti-gamma corrected.

Every color in any color chip in the material room, whether a material or a light or the background, is assumed to be a color you picked on the basis of how it looked. That's a gamma corrected value. It gets changed to linear.

[ Lots of rendering equation in the middle, none of which you need to understand. ]

All the light sources, equations, reflections, etc. (all the factors adding up to a color on a pixel) are added together linearly.

The final value is gamma corrected.

Thanks. Glad you didn't have to explain all that typing on a moving iPad on a starboard tack. This is what you were driving at before: not everything is linearised with material GC. Got it.

Quote - ...

Every color in any color chip in the material room, whether a material or a light or the background, is assumed to be a color you picked on the basis of how it looked. That's a gamma corrected value. It gets changed to linear.

...

All the light sources, equations, reflections, etc. (all the factors adding up to a color on a pixel) are added together linearly.

The final value is gamma corrected.

BB, thanks for the explanations on render GC.  Would you take a look at the example below and let me know if my understanding of render GC is correct (or incorrect)?

I bought a fur product for the Millenium Cat from a vendor at Content Paradise.  The fur is a collection of props that look like hairs.  As expected, the fur shader is not gamma corrected.  Here's the shader in pseudo matmatic notations:

n = Noise();
n.x_Index = 4 * ImageMap("BlueSiamese.jpg");
n.y_Index = 4 * ImageMap("BlueSiamese.jpg");
n.z_Index = 4 * ImageMap("BlueSiamese.jpg");
n.min = 0.3;
n.max = 0.4;

h = Hair();
h.Root_Color = BLACK * n;
h.Tip_Color = WHITE * n;
h.Specular_Color = BLACK;
h.Highlight_Size = 0.01;
h.Root_Softness = 0.25;

s = EmptySurface().Alternate_Diffuse = h;

If I turn on render GC, will it first anti-GC each color and image and then GC the end result, as shown below?

n.x_Index = 4 * AGC(ImageMap("BlueSiamese.jpg"));
n.y_Index = 4 * AGC(ImageMap("BlueSiamese.jpg"));
n.z_Index = 4 * AGC(ImageMap("BlueSiamese.jpg"));

h.Root_Color = AGC(BLACK) * n;
h.Tip_Color = AGC(WHITE) * n;
h.Specular_Color = AGC(BLACK);

s = EmptySurface().Alternate_Diffuse = GC(h);

Will appreciate any advice you provide.  Thanks.

Oops sorry BB.  After re-reading your explanations a few more times, I realize I didn't get all of what you mean.  I also missed a few crucial bits in the cat fur shader.  So here's the original "non-GC" cat fur shader.

n = Noise();
n.x_Index = 4 * ImageMap("BlueSiamese.jpg");
n.y_Index = 4 * ImageMap("BlueSiamese.jpg");
n.z_Index = 4 * ImageMap("BlueSiamese.jpg");
n.min = 0.3;
n.max = 0.4;

h = Hair();
h.Root_Color = BLACK * n;
h.Tip_Color = WHITE * n;
h.Specular_Color = BLACK;
h.Highlight_Size = 0.01;
h.Root_Softness = 0.25;

s = EmptySurface().Alternate_Diffuse = BLACK * h;

s.Diffuse_Color = WHITE * ImageMap("BlueSiamese.jpg");

s.Diffuse_Value = 1.0;

Here's what I'm guessing render GC will do.

n.x_Index = 4 * AGC(ImageMap("BlueSiamese.jpg"));
n.y_Index = 4 * AGC(ImageMap("BlueSiamese.jpg"));
n.z_Index = 4 * AGC(ImageMap("BlueSiamese.jpg"));

h.Root_Color = AGC(BLACK) * n;
h.Tip_Color = AGC(WHITE) * n;
h.Specular_Color = AGC(BLACK);

s.Alternate_Diffuse = AGC(BLACK) * h;

s.Diffuse_Color = AGC(WHITE) * AGC(ImageMap("BlueSiamese.jpg"));

output = GC((s.Diffuse_Color * s.Diffuse_Value) + s.Alternate_Diffuse);

Am I correct or just totally dead wrong?

Blue Siamese.  Left image = Non-GC.  Right image = render GC.

Correction.  In my recent post, the line

      s = EmptySurface().Alternate_Diffuse = BLACK * h;

should have been

      s = EmptySurface().Alternate_Diffuse(BLACK * h);

Sorry about the boo boo.

Quote - That would be one reason - but the bigger reason, one I can't explain the reason for, HBorre - is that my makeup shaders don't behave right with the renderer GC... but work fine with the material based GC. Yes, I've made the gamma correction 1 for all non-colour maps, but what happens is the colours aren't anywhere near as saturated, so I have to turn the values up. I'll show you what I mean.

...

Robynsveil, in the thread below the OP set the custom gamma to 0.1 for the eyebrows and lashes.  I don't know why it worked in render GC but it worked.

http://www.renderosity.com/mod/forumpro/showthread.php?message_id=3810471&ebot_calc_page#message_3810471

might want to be careful on the streagth of the gamma correction it does remove detail from the image, too mush might as well be poser 4 too little might as well be poser 4

cats ears are too red i would use a gamma correction on that to make them a little more skin tone colored looks like an ear infection in both his ears