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So I got inspired by another thread and dinked for about an hour to put this together.

 

[attachmentid=21884]

 

It brings up something we've discussed in other threads for Tin Woodman, reflection and how to make it better in darkly lit situations. Yves is working on solutions (I think) but I wanted to get input on things that might improve reflection in AM and get input on this guy as well ;-)

 

The thing I find I miss most is a reflective color. Is there a way to do this and I'm just missing it? One thing that kills metals is when they reflect to much color from the environment if they have color themselves, like gold or brass or copper.

 

The other thing is how to fake a brighter more reflective surface while keeping the reflection high. If you crank it up and the environment is dark you end up with a dark character (realistic sure but not good for cinematography). being able to add a diffuse element to the shading while still keeping the reflection high could fake this. I don't know how you'd do it and it could really be used in wrong ways, but theres got to be some way to pump up the metals brightness without blowing out your background with lights and bright colors.

 

Any ideas?

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It brings up something we've discussed in other threads for Tin Woodman, reflection and how to make it better in darkly lit situations. Yves is working on solutions (I think) but I wanted to get input on things that might improve reflection in AM

I'm not working on solutions. I think the solutions are already implemented in A:M.

 

Any ideas?
Oh Yeah! I'm glad you ask because this will allow me to explain a couple things about reflections.

 

and get input on this guy as well
The model itself is absolutely awesome. I like the pose. Good use of foreshortening. Something is bothering me with the composition but I can't put my finger on what it is exactly. I have the impression that his body is placed too high and too left in the compositon. But for a one hour work, you certainly didn't take the time to tweak the composition to your liking. The ankle pivot seems placed too high and it is difficult to separate the character from the background. But that is the issue we are going to discuss.

 

The thing I find I miss most is a reflective color. Is there a way to do this and I'm just missing it? One thing that kills metals is when they reflect to much color from the environment if they have color themselves, like gold or brass or copper.
The properties you are looking for are "Reflection Filter" and "Reflective Blend" right under "Reflectivity".

 

Metals will usually have a reflection filter of 100% and a reflective blend of 100%.

 

Reflective Blend controld how the reflected colors are blended into the base diffuse color. At 0%, the reflected colors will be added to the base diffuse color and at 100%, the reflected colors will replace the diffuse colors in proportion to the reflectivity. If reflectivity is set to 40% and blend is set to 100%, the final color will be 60% of the base diffuse color and 60% of the reflected colors. If Reflectivity is 100% and blend is set to 100%, then there will be no contribution coming the diffuse color. For realistic reflective surfaces, reflective blend should be set to 100% but this can be adjusted according to the particular needs of different projects.

 

A Reflective Blend of 0% can produce unrealistic reflections because the reflections are added to the base diffuse color so the reflected colors will be brighter than the actual objects that are being reflected. Say a surface with some diffuse color, 100% reflectivity and 0% blend. because the base diffuse color is added to the 100% reflections, the resulting color will clearly be brighter than the object reflected.

 

Reflective Filter works with the specular color. It will filter the reflected colors using the specular colors. This can allow to imitate several types of materials. Most of the time, you don't need to set a specific specular color. In this case, the reflective color will use the diffuse color and most of the time, for most of the materials, this is exactly what you want.

 

Some special materials where you would want to set a different specular color are plastics or any clear coated materials like varnished wood for instance. Those materials are layered materials and the layer that actually specularly reflects colors is a different layer than the one that diffusely reflects colors. In varnished wood, for instance, the wood is covered with a transparent varnish. In this case, you would want to set the specular color to the color of the varnish. Plastic is layered because you have colored pigments suspended in a clear substrate so the pigments produce a diffuse reflection element and the substrate will produce the specular reflection element. Because the clear coat is usually much smoother than the underlying material or pigments, it is the coating that produce the charateristicly sharp reflections.

 

There exist other types of coated materials that are much more complex than that such as some metal flake car paints. But this is much more involved to simulate in CG.

 

Most other materials just reflect and filter light using the diffuse color. This includes metals too.

 

Layered materials must have their reflectivity set to less than 100% to let the diffuse reflection component coming from the underlying material or pigments to show through. In fact, the reflectivity would be the inverse of the transparency of the clear coat material. That is why, when we set reflectivity to significantly less than 100% on any material, it starts to look like coated materials.

 

The recipe for realistic metals is, Reflectivity, Reflection Filter and Reflective Blend all set to 100% and the particular metal reflectivity color set in the diffuse color. Some metal reflectivity colors can be found on Webmineral.com. For instance here is the Webmineral Silver data sheet. If you scroll down to the section called "Optical Properties of Silver", you will see a spectrum chart along with the RGB representation in the "S R(l)" column. Some metals like Tin are anisotropic and thus have two reflectivities. Anyway, if you use a color picker (or look in the source code of that page) you will find out that the RGB representation is F0EAD7 or R:240, G:234, B:215 or R:94%, G:91%, B:84%. So Silver reflectivity if pinkish and that would be our diffuse color.

 

Why this recipe? By setting Reflectivity to 100% but also both Reflective Blend and Reflection Filter to 100% we get a surface that will reflect the light at the required percentage of reflectivity for each RGB channels. We effectively end up with a surface that have 94% reflectivity on the Red channel, 91% reflectivity on the Green channel, and 84% reflectivity on the blue channel which is the characteristic reflectivity of Silver.

 

If Silver is pure, that is it is not oxidized, nor covered with dirt, then its reflectivity will be R:94%, G:91%, B:84% (or higher because of the Fresnel effect). But the next most important surface property that will affect its appearance is the surface roughness. If the silver surface is perfectly smooth, it will act like a mirror and as the silver surface gets rougher, it will act less like a mirror and start reflect light coming from more distributed locations. In other words, it will look more diffuse. This is where Soft Reflection comes into the picture.

 

Soft Reflection softness is controlled by the Specularity Size. The larger the specularity size, the rougher will look the reflections if Soft Reflections is turned ON.

 

BTW, noticed how many reflectivity attributes are controled by Specularity properties? That is because Reflectivity and Specularity are two different CG tricks to help simulate the same physical surface properties. Reflectivity controls how surrounding objects are reflected off the surface of an object while Specularity controls how the lights are reflected off the surface of an object. For this very reason, for more realistic renders, the Specular Intensity should match the Reflectivity. That is for a 60% reflective surface, its Specular Intensity should also be set to 60%.

 

The other thing is how to fake a brighter more reflective surface while keeping the reflection high. If you crank it up and the environment is dark you end up with a dark character (realistic sure but not good for cinematography). being able to add a diffuse element to the shading while still keeping the reflection high could fake this. I don't know how you'd do it and it could really be used in wrong ways, but theres got to be some way to pump up the metals brightness without blowing out your background with lights and bright colors.

 

If you set the Reflective Blend to 0%, the reflections will add to the diffuse color. This should give you what you are looking for since Silver is quite already a pale color. And you can adjust this Reflective Blend to suit your requirements.

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Wow.. thanks Yves.. you've given me a good education. Part of my problem was coming at it from other 3d apps which break some functions out to multiple settings. I see now that AM has it all there, its just a more fine tuned dance between fewer attributes. I'll see if I can apply this to SS and Tinman to get the effects I want.

 

Thanks again.

 

Oh and you are right about the ankle... it bugged me to.. I actually lengthened his legs in the model and forgot to lengthen the shin bones ;-)

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Yves, this is really great information and a clear, concise breakdown of these various qualities. Thanks!

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Oups! Just rereading my post, I saw that I made an important error. I corrected it in the original post. It was about this statement:

If you set the Reflective Blend to 100%, the reflections will add to the diffuse color. This should give you what you are looking for since Silver is quite already a pale color. And you can adjust this Reflective Blend to suit your requirements.

It is not 100% of course for reflective blend to add the difuse color to the reflections. It should read 0%.

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Hi guys,

 

One thing I wanted to ask about is why not add something to mimic the look of a metal's micro surface bumps and the way they break up the specular elements? This may not be the right name for it, I was also trying to talk about this last night on the TWO chat but couldn't describe it well enough then either! But a picture is worth a thousand words so I've included one, on the left is a photograph of a metal pole, on the right, our beloved Tinman. This metal pole might show the effect too much, but don't metal surfaces exhibit this to some degree no matter how smooth they are?

 

I think when I look at the Tinman this is part of what seems missing. His specular shine is so perfect it's... well, I don't want to say like plastic, but... I'd say it's just a bit too perfect. Would this idea help separate both the Tinman and the Silver Surfer from the background or in general just add to the look of metal?

 

As this is turning into a very educational thread, please jump in and clarify if I'm on the wrong track here.

 

thanks!

 

-Jim

metal_example.jpg

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If you could have a tileable image to use for a reflection map, that might be a good way to get that effect. Another way could be a material that had a combiner and differing reflectivity.

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Jim.. what you are talking about is the surface roughness, i.e brushed metal versus a chrome steel bearing. William is right.. you can mimic that with a texture bump or material. Not all metals have it, or would appear to have it to the naked eye, And it wouldn't be obvious from the camera distance in many thanks to antialiasing.

 

I've been looking at metals all day now and I've noticed one thing related to this that AM doesn't seem to simulate. When the surface is rough and reflections are soft. They are more focused up close and get blurrier and fade more with distance. The fading we can do but the blurring isn't there yet. its a fine point of course, but might add to the realism on TM. Maybe you could have a near and far reflection filter with each having a different blurriness?

 

This brings up another question. Does DOF only apply to the camera? ie.. are reflections of far off objects blurred as well? I know something like this could blow the render times through the roof, but I thought after Yves educational post that we could start getting into specifics.

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First, that was an excellent explanation/lesson by Yves.

 

Second, doesn't the brushed metal material come close (from what I remember) to Jim's question/request?

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One thing I wanted to ask about is why not add something to mimic the look of a metal's micro surface bumps and the way they break up the specular elements? This may not be the right name for it, I was also trying to talk about this last night on the TWO chat but couldn't describe it well enough then either! But a picture is worth a thousand words so I've included one, on the left is a photograph of a metal pole, on the right, our beloved Tinman. This metal pole might show the effect too much, but don't metal surfaces exhibit this to some degree no matter how smooth they are?

You used the qualificative "anisotropic" yesterday. That is the right word for what you are describing with the pole. But the anisotropy is usually not a characteristic of metal per se. It is a characteristic of the manufacturing process. Anisotropy is visible when the scratches on a surface are directionally oriented in one direction more than others. When this is the case, the reflection softness is tighter in one direction then in its perpendicular direction.

 

Metal surfaces come in different smoothness. Some silverware are so buffed that they are almost like mirrors. On the other side of the spectrum, some surfaces are explicitly made rough because we have to handle them and we don.t want them to slip out of our hands. Another cause may be erosion. An initially very smooth silverware could be rendered relatively dull (rough) because its been used and washed so often.

 

Indeed, the dull or rough look is caused by micro (or not so micro) bumps.

 

I think when I look at the Tinman this is part of what seems missing. His specular shine is so perfect it's... well, I don't want to say like plastic, but... I'd say it's just a bit too perfect. Would this idea help separate both the Tinman and the Silver Surfer from the background or in general just add to the look of metal?
That is what soft reflection is supposed to give you. We don't do anisotropic reflections though. We have an anisotropic shader but it is only affects the specularity.

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Jim.. what you are talking about is the surface roughness, i.e brushed metal versus a chrome steel bearing. William is right.. you can mimic that with a texture bump or material. Not all metals have it, or would appear to have it to the naked eye, And it wouldn't be obvious from the camera distance in many thanks to antialiasing.

Depending on the distance we are observing the surface and on the size of the surface bumps, we will simulate them in different ways and each way have a name. There are three types of CG roughness simulations in a continuum from macro to micro: geometric details, textures, BRDF (Bidirectional Reflectance Distribution Function). At the "Geometric level of details, you just model the surface bumps and render. At the texture level, you apply a bump texture and render with antialiasing. At the BRDF level, you just simulate the look.

 

I've been looking at metals all day now and I've noticed one thing related to this that AM doesn't seem to simulate. When the surface is rough and reflections are soft. They are more focused up close and get blurrier and fade more with distance. The fading we can do but the blurring isn't there yet. its a fine point of course, but might add to the realism on TM. Maybe you could have a near and far reflection filter with each having a different blurriness?
If you look closely, soft reflection is doing exactly that, including the bluring with distance. Soft Reflection is not just a post effect. It is the actual simulation of the diffusion of reflections.

 

Soft Reflection is simulating the BRDF of a rough isotropic surface. And yes, it pushes render time through the roof because in order to do that, the renderer must not only shoot one reflection ray but must shoot as many as is required to produce the soft reflection look. The larger the soft reflection spread, the more the number of reflection rays that must be cast in the scene from any pixel. The reflection rays are casted from inside a cone starting on the surface and spreading in the environment. The smaller the specularity size, the tighter the reflection cone and thus the sharper the reflected images. And conversely, the larger the specularity size, the wider the reflection cone spread and thus the blurrier the reflected images.

 

The blur fading with distance is a direct consequence of sampling reflection rays from inside a cone. A reflected object sitting at, lets say 10cm from a soft reflective surface will look twice as blurry as another object sitting at 5cm because the blur radius is twice as large.

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The blur fading with distance is a direct consequence of sampling reflection rays from inside a cone. A reflected object sitting at, lets say 10cm from a soft reflective surface will look twice as blurry as another object sitting at 5cm because the blur radius is twice as large.

 

Awesome! I had a feeling, knowing your predisposition for "realism" that this might be the case. Now I need to test and figure these things out.

 

Thanks for the lesson Yves.

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Ohhh yeah my favorite leesly known hero the silver surfer

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GREAT THREAD!

 

I loved explanations about reflectivity!

 

I love everything about Silver sulfer (one of my favourite superheroes)

 

little remark: his pose could benefit from simpler line of movement (you kow: lilne that describes positions of the body and limbs) it would make better statement and illusion of speed...

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