REAL LIFE EXAMPLES FOR Computer Graphics Imaging

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REAL LIFE EXAMPLES FOR Computer Graphics Imaging

Post by v_wrangler on Tue Sep 07, 2010 11:48 pm

I'm making a thread here to post photos of real-world examples to serve as a starting point when you create materials, lighting or setup your renderings. This will be constantly updated. I will post the first pictures within the day.

Area Shadows

I'm sure you've all heard about it. The concept is simple. Real life shadows from light sources whether they are from natural or artificical lighting tends to blur the farther they are from the occluding object. The blurriness depends on the size, angle and location of the light sources. This is of course the reason why your shadows tend to be sharp during mid-day and the sun is up compared to the early mornings or pre-dawn when the sun is down.

To mimic them in CG all you need to do is use area shadows at the expense of rendering time.





Specular Highlights

Round specular highlights are just remnants of the old pre-raytracing days when rendering raytrace reflections are time -consuming due to the slowness of computer computations back then. So to get around this limitation, software devised the round speculars to mimic the real highlights.

ADD: Another reason for this is the approximation of cg lighting models where all light sources are considered as point lights. This makes sense if the virtual situation you are trying to mimic matches that of the round, bulb light sources. With the advent of planar lights and object lights such as those of vray, round speculars are no longer a limitation or an excuse but more of a sensible choice.

Highlights and specularity are actually reflections of the bright light sources around you. If you take a look at any shiny object in your table, the highlights you see are actually the reflections of the window, the ceiling lights or any other bright light sources in the proximity.

While it is not really bad to use speculars and glosiness from your material setups, you can do away with the CGesque round highlights by masking your specularities with BW images of window openings or anything that would break the round regular shapes of the CG speculars. Most comon way to get over the look is to make sure you model your light sources, get rid of the speculars in the material and instead, raytrace anything that has any slight hint of specularity.

Here's an image of a camera shot in the studio and the actual scene when the shoot was staged. You will notice that the speculars in the real image was actually the reflections of the diffusers and the reflectors in the studio.





And how those shiny reflective car images were shot:




Speculars (Reflections) and Diffuse : The Two Major Component of the Material

The two major component of a material can be summed as the Specular (the reflections of the light source as I mentioned above) and the Diffuse. Their colors, properties as well as their proportion dictates the kind of material the object is made of. Knowing their properties can serve as a foundation when you recreate materials in your favorite cg application.

When light hits an object, that energy is reflected back as one of the two components above. The shiny Specular highlights (reflections of the light source) and the Diffuse energy (the actual color of the object).


The billiard balls above illustrate both the diffuse and the specular components combined. The specular component of non-metals (dialectrics) which I'll discuss in future installments, are actually very mild. This is a very important hint to consider when designing materials.

The most common mistake anong cg artists both old and new ones is to pump the specular reflectance properties of objects way too high making them look unnaturally fake and cg-looking.


The two components (Specularity and Diffuse) make up 100% of a material. (for brevity - I'll be referring to the reflections of the light sources as specular or specularity from hereon)

If 60% of this material is diffuse energy then it can only reflect back 40% of specularity. If the diffuse part increases, then specularity decreases and vice-versa. Remember that no object will reflect back more energy (light) than it receives. Except of course if its a dayglo (daylight bulbs).

The pingpong ball has a very high diffuse component (matte) and very low specularity.



And the mirror can be considered as a highly specular material with almost no diffuse property.




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Just to sum it all, there are so many hints around you that could help you decide in setting up photorealism and lighting in your 3d application of choice. The secret is research and constant observation. You will never be able to mimic anything unless you know how the real thing is staged by nature or by clever photographers. As we always say, Know the rules before you break 'em.


Last edited by v_wrangler on Sun Sep 26, 2010 2:56 pm; edited 12 times in total
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Re: REAL LIFE EXAMPLES FOR Computer Graphics Imaging

Post by v_wrangler on Sun Sep 12, 2010 8:16 pm

I just added a two images. more to come.
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Re: REAL LIFE EXAMPLES FOR Computer Graphics Imaging

Post by arkiedmund on Sun Sep 12, 2010 9:02 pm

Ayan..area shadows, can be set via max's default direct light. Those who started rendering without jumping to vraysun's and vray cameras, know this feature very well.

But for those who started with max using vray's physical sun feature, my best guess to mimicking the area shadows feature that a standard light can offer is to set the sun's size multiplier to a higher value.

Looking forward to the next set of images.

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Re: REAL LIFE EXAMPLES FOR Computer Graphics Imaging

Post by v_wrangler on Sun Sep 12, 2010 9:16 pm

I also added a few about specularities. If there are questions, just post and will try to update the images or explain further.

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Re: REAL LIFE EXAMPLES FOR Computer Graphics Imaging

Post by arkiedmund on Sun Sep 12, 2010 9:24 pm

bookmarked.

Speaking of speculars...different materials have their own specular quality, am i right sir vertex?

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Re: REAL LIFE EXAMPLES FOR Computer Graphics Imaging

Post by v_wrangler on Sun Sep 12, 2010 9:30 pm

Ed, You are correct. It can be summed into two. Metals and non metals. I'll expand on the two later when i find time.

Thanks Neil!

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Re: REAL LIFE EXAMPLES FOR Computer Graphics Imaging

Post by v_wrangler on Sat Sep 25, 2010 7:32 am

I just added some more information about Material Components: the Specular and the Diffuse.

I'll write about metals and non-metals in the next installment.

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Re: REAL LIFE EXAMPLES FOR Computer Graphics Imaging

Post by v_wrangler on Thu Jun 28, 2012 7:38 am

I've almost completely forgotten about this...

time to write the supplements!
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Re: REAL LIFE EXAMPLES FOR Computer Graphics Imaging

Post by jamesalbert on Tue Jan 06, 2015 9:36 pm

Sir please update the images, thanks
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Re: REAL LIFE EXAMPLES FOR Computer Graphics Imaging

Post by v_wrangler on Tue Jan 06, 2015 9:39 pm

Apologies it took years to update I'll try as soon as I find time...
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