I'm a relatively new member here (about a month old).
I'm a 3D artist specializing in environments and ArchViz.
I'm seeking to refine my artistic abilities particularly in the realm of photorealistic rendering(which is a monumentally difficult skill).
A big part of that is understanding attributes of real world materials.
In the world of 3D, materials are categorized as either dielectric or conductive.
The logic being that conductive materials such as metals transfer energy, which results in colored specular highlights and/or reflection.
Specular highlights are the simulation of reflected light sources, which in the real world is simply reflectance but when recreating this effect on a computer it's more resource efficient in most cases to use the faked reflectance model of specular highlights.
Then there's dielectric materials such as plastics, which are actually suspensions of colored particles in a clear polymer substance.
These don't transfer energy, so they don't result in colored specular highlights.
I'm not sure if anyone is already familiar with what I'm talking about, which is why I thought that little background explanation was necessary.
What I'm after is simply resources which I can collect and use to gain a better understanding of material properties.
I'm really not too familiar with the physics behind material properties, but I want to change that.
I do scour the web for this information, and have found some helpful data.
What I'm asking for here is if anyone can point me in the direction of some technical resources I can use to further my understanding.
This seems like an excellent place to acquire this knowledge.
I'll be very appreciative of any suggestions or insights that any of you think could help me to achieve this goal.
I'm not asking anyone to teach me about material properties or to do the footwork for me.
Just asking for anyone to point me in some direction where I can find information on the physics behind different materials.
Thanks for your time.
Hi Dtoxxx!
I don't have any site in mind to explain the material's optical properties. But here are a few elements.
Metals reflect light, but not necessarily all colours, and not necessarily in a specular way.
Copper or gold have a pronounced colour because they absorb certain wavelengths instead of reflecting them. Each metal has a distinctive colour (silver for instance) though less marked.
Specular reflection is linked to the smoothness of the surface. Rough metal will create a diffuse reflection.
Some reflection also occurs with insulators. You can notice it on glass, especially at flat angles. By arranging many thin layers of transparent insulators, one can achieve very good mirrors for one colour - far better than any metal.
Many plastics are naturally clear or transparent, others have their own colour. PVC is grey, you won't get it clear. Polyimide is brown. Aramide is yellow.
I don't have any site in mind to explain the material's optical properties. But here are a few elements.
Metals reflect light, but not necessarily all colours, and not necessarily in a specular way.
Copper or gold have a pronounced colour because they absorb certain wavelengths instead of reflecting them. Each metal has a distinctive colour (silver for instance) though less marked.
Specular reflection is linked to the smoothness of the surface. Rough metal will create a diffuse reflection.
Some reflection also occurs with insulators. You can notice it on glass, especially at flat angles. By arranging many thin layers of transparent insulators, one can achieve very good mirrors for one colour - far better than any metal.
Many plastics are naturally clear or transparent, others have their own colour. PVC is grey, you won't get it clear. Polyimide is brown. Aramide is yellow.
You can do what I do: Use high res greyscale bitmaps to model the texture of an object based on high res microscope images of the surface. It turns out pretty well. All the specular, diffuse, ambient tools in 3d modelling programs are really just approximations of this.
It takes forever to render, though. Even with daisy-chained processors.
It takes forever to render, though. Even with daisy-chained processors.
Nice!
So you guys do 3D also?
Yes, in this case I personally find the use of HDRI images to create better diffuse reflections than the specular model.
However, you find yourself in a peculiar situation if the surface has any luminance effect from the light, such as subsurface scattering.
That requires you to create lights that match the HDRI but are also powerful enough to drive the effect.
Very easy to wash out your highlights.
I'm just now getting into using a linear workflow and gamma correction, which makes a huge difference.
I'm kicking myself for not doing it sooner.
Yes, in this case I personally find the use of HDRI images to create better diffuse reflections than the specular model.
However, you find yourself in a peculiar situation if the surface has any luminance effect from the light, such as subsurface scattering.
That requires you to create lights that match the HDRI but are also powerful enough to drive the effect.
Very easy to wash out your highlights.
I'm just now getting into using a linear workflow and gamma correction, which makes a huge difference.
I'm kicking myself for not doing it sooner.
Some reflection also occurs with insulators. You can notice it on glass, especially at flat angles. By arranging many thin layers of transparent insulators, one can achieve very good mirrors for one colour - far better than any metal.
Do you mean this in a "material reality" sense, or from a "simulated reality" sense?
By that I mean are you saying that when creating a shader for a 3D object, place many thin transparent layers with the same properties of an insulator?
Or do you mean when actually working with physical materials?
Because that sounds like something I'd like to try.
I'd like to see a renderer able to deal with light and surface properties in this way.
Where you could use a chart that tells what wavelengths are absorbed/reflected by specific surfaces, and input that value into your material attributes.
Similar to the way you can specify the refractive index of a transparent material using the IOR table available on the web.
I'd like to see a renderer able to deal with light and surface properties in this way.
Where you could use a chart that tells what wavelengths are absorbed/reflected by specific surfaces, and input that value into your material attributes.
Similar to the way you can specify the refractive index of a transparent material using the IOR table available on the web.
Many plastics are naturally clear or transparent, others have their own colour. PVC is grey, you won't get it clear. Polyimide is brown. Aramide is yellow.
What makes them colored though?
Is it diffuse particles suspended in a polymer base?
That sounds fascinating.
How does one acquire high rez grayscales like that? Aside from having access to the equipment?
Do you have any examples of renders produced with this method?
That sounds like exactly what I'm looking for.
What kind of resolution are we talking about here?
8K+?
Higher?
Are they 32bit floating point images?
When you say they take forever to render, what kind of render times do you get?
On what kind of hardware?
I'm on an Apple PowerMac G5 quad.
Still using the older PPC cpu.
What kind of work do you guys do?
What 3D apps do you use, if any?
I use Cinema4D 10.1 studio bundle.
Sadly, I'm limited by the speed and lower quality of the cinema4d advanced render.
Can't afford V-Ray yet.
Thanks alot for the info.
I look forward to hearing more.
So you guys do 3D also?
QUOTE
Specular reflection is linked to the smoothness of the surface. Rough metal will create a diffuse reflection.
Yes, in this case I personally find the use of HDRI images to create better diffuse reflections than the specular model.
However, you find yourself in a peculiar situation if the surface has any luminance effect from the light, such as subsurface scattering.
That requires you to create lights that match the HDRI but are also powerful enough to drive the effect.
Very easy to wash out your highlights.
I'm just now getting into using a linear workflow and gamma correction, which makes a huge difference.
I'm kicking myself for not doing it sooner.
QUOTE (->
| QUOTE |
| Specular reflection is linked to the smoothness of the surface. Rough metal will create a diffuse reflection. |
Yes, in this case I personally find the use of HDRI images to create better diffuse reflections than the specular model.
However, you find yourself in a peculiar situation if the surface has any luminance effect from the light, such as subsurface scattering.
That requires you to create lights that match the HDRI but are also powerful enough to drive the effect.
Very easy to wash out your highlights.
I'm just now getting into using a linear workflow and gamma correction, which makes a huge difference.
I'm kicking myself for not doing it sooner.
Some reflection also occurs with insulators. You can notice it on glass, especially at flat angles. By arranging many thin layers of transparent insulators, one can achieve very good mirrors for one colour - far better than any metal.
Do you mean this in a "material reality" sense, or from a "simulated reality" sense?
By that I mean are you saying that when creating a shader for a 3D object, place many thin transparent layers with the same properties of an insulator?
Or do you mean when actually working with physical materials?
Because that sounds like something I'd like to try.
QUOTE
Copper or gold have a pronounced colour because they absorb certain wavelengths instead of reflecting them. Each metal has a distinctive colour (silver for instance) though less marked.
I'd like to see a renderer able to deal with light and surface properties in this way.
Where you could use a chart that tells what wavelengths are absorbed/reflected by specific surfaces, and input that value into your material attributes.
Similar to the way you can specify the refractive index of a transparent material using the IOR table available on the web.
QUOTE (->
| QUOTE |
| Copper or gold have a pronounced colour because they absorb certain wavelengths instead of reflecting them. Each metal has a distinctive colour (silver for instance) though less marked. |
I'd like to see a renderer able to deal with light and surface properties in this way.
Where you could use a chart that tells what wavelengths are absorbed/reflected by specific surfaces, and input that value into your material attributes.
Similar to the way you can specify the refractive index of a transparent material using the IOR table available on the web.
Many plastics are naturally clear or transparent, others have their own colour. PVC is grey, you won't get it clear. Polyimide is brown. Aramide is yellow.
What makes them colored though?
Is it diffuse particles suspended in a polymer base?
QUOTE
You can do what I do: Use high res greyscale bitmaps to model the texture of an object based on high res microscope images of the surface. It turns out pretty well. All the specular, diffuse, ambient tools in 3d modelling programs are really just approximations of this.
It takes forever to render, though. Even with daisy-chained processors.
It takes forever to render, though. Even with daisy-chained processors.
That sounds fascinating.
How does one acquire high rez grayscales like that? Aside from having access to the equipment?
Do you have any examples of renders produced with this method?
That sounds like exactly what I'm looking for.
What kind of resolution are we talking about here?
8K+?
Higher?
Are they 32bit floating point images?
When you say they take forever to render, what kind of render times do you get?
On what kind of hardware?
I'm on an Apple PowerMac G5 quad.
Still using the older PPC cpu.
What kind of work do you guys do?
What 3D apps do you use, if any?
I use Cinema4D 10.1 studio bundle.
Sadly, I'm limited by the speed and lower quality of the cinema4d advanced render.
Can't afford V-Ray yet.
Thanks alot for the info.
I look forward to hearing more.
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