Mixed tips for realistic renders

Hi people. I spend a few days searching informations to learn about the big topic in our beloved discipline: realistic renders in our beloved Blender Cycles.

How to make renders feeling like a photography, or like what we see with our own eyes?

Notice that we have two choices: make them look like photos or human eye perception. Different things, different look. The human eyes catch way more color values than usual digital devices. If you want to build a fluorescent tube like a photo, you can leave it uniformly white and full bright. The same fluorescent tube in the human eye’s view is made of gradients of tones and colors. Only the good photographers (when they have time) take HDR pictures to catch details in the highlights to render what the eye can see. It’s a choice to make, but 3D gives us the ability to create world closer to the human eye than photography in this aspect.

First thought: observe the beauty of reality

The philo-spiritual-thing paragraph. It’s not for all a natural thing to take time to watch reality. You have to stop thinking, stop moving, just be present to what you’re looking at. If the phrase beeing present rings a bell to you, I strongly recommend to read The Power of Now from Eckart Tolle. This guy found the most simple, honest and right words to make us be present to ourselves. A key element ot live a good life, and to be a happy a good artist. To me, the quality of art is linked to the quality of living. Beeing a balanced person enlarge the perception of things, visual, sound, touch. Enlarging what we see cannot be a bad thing. It gives the ability to see more in detail and more global at the same time. It gives the ability to learn and to grow, to understand the world better.
Eckart Tolle said once: “Some things are so close to us that we don’t see them anymore”. Observe reality closely, the beauty of it, even the apparent ugliness (that is not so ugly). Detail shadows areas, highlights and all that makes a good photo or a nice spot to look at. That the key part to make any artwork, drawing, painting, photography, sculpting and digital imaging.

Every detail counts

Forget to count only on lighting or texturing. All matters. Everything in the scene add his contribution to the real-feel. Like many art form, every step of the process is a part of the journey ans have its importance to the final result.


Before any test of my own, here is the theory. A list of 10 things to do for a good rendering by Jeremy Birn, technical director at Pixar since 2002 (I think he knows his job), with my own comments. Even if he works with the standard in industry Maya, we can use this knowledge to Blender. 3D is 3D with different tools. Know your tool and you’ll make a great job.
Down I added my own tips.


1 – Use linear workflow

Blender already works linear (1.0 gamma). Read the Blender manual.
It seems that “linear” is a short term to say scene-referred (vs display-referred) workflow. Many detai
ls in the PDF from the cinematic color page. Since version 2.64 Blender uses the ColorIO system for the color management, that is the system used in cinema industry since 2003.

So Blend happy without worrying about this, except for the render. The manual says:
Rendering and compositing is best done in scene linear color space, which corresponds more closely to nature, and makes computations more physically accurate. I’m figuring how to work with .EXR files. Not easy, color and tones goes bezerk. Compatibility with existing files should mostly be preserved. Files that had color management enabled should be entirely compatible.

Anyway, for thos who uses Photoshop, it seems that is not so easy to make color accurate textures in it. Read here how to make an ICC profile for it. And if you want to explode your brain, read this. Then go eat a cookie. But none of this color profiles things matters if you don’t have a calibrated monitor. OK? Further color management ressources here.

About the importance of working with the right gamma.
Here the Renderman Linear Workflow page. Look in the middle of this page, the 3 main color pictures. The 3rd is the correct one and jeeze, suddenly the scene looks real, even with simple non realistic objects.

This slideshow requires JavaScript.

2 – Solo the lights

Test every light source independently to see what the effect of each light. Sometimes we end up adding more light that is necessary. Every light has a purpose, a color, an intensity. Just observe and anticipates what every light does.
The lamp setup can be very simple: a sun light and a skydome (an half sphere with the sky texture on it, equivalent of an HDR environement) in some cases. More often, use a main light, doubled with a spill light, a skydome or any global light, a rim light and what Jeremy Birn call a kick light. It’s a more larger rim light. Graphic to come.
Here some tips from the very good site Chocofur.

3 – Beware of light/object’s names

Just stay practical, name thing to retrieve them later.

4 – Nail the character’s eyes

Very specific to the subject. Good eyes make a living character.

5 – Use extra bounce colors/lights

– Place where necessary an area or a point light to add indirect lighting in specific places. For example where a sun beam hit the floor near a shadow area. Blender Cycles do it well but often miss some power in the bounced light. Add a small area or a mesh/plane, turn it to emitter and choose the color corresponding to the color surface. Maybe more saturated, just try.
– Raise saturation in some cases when the shadows areas becomes too neutral. Here too Cycles tend to make some dark areas losing color information.

6 – Divide scene in different color spaces

It’s about composition an creating mood in the scene. Can be contrast, harmony, both, lines defining areas in the picture, color temperature, anything. If that works, good. If they’re is too much saturation, you can desatureate later. Bringing up saturation makes pixels less good.

7 – Add spill light

Very important and complementary to adding local bouncing lights. Example: duplicate (1 or 2 times) the main sun lamp; move it/them a little bit towards its target to make it/them visible in the interface; make it/them dimmer, warmer or colder and with larger shadows (for ex. main lamp: 1 cm, spill lamp: 50 cm). Make it/them a slightly different color, it adds subtle variation in the spill light inside shadows. Simple efficient trick.

8 – Use natural colors outside extreme levels

Very very important topic. Who practice digital photography knows that the first thing to do before and after the shoot is to adjust the white balance (the temperature color). A photo too cold or too warm is flat. When you find the correct point where you discern the cold from the warms, you are on the good way. A good render must have some cold and warm parts, like any photo. It means an even slightly difference between warm and cold parts. It can be 2 lamps (1 cyan and 1 orange) or 1 warm lamp on a cold texture. Anything that gives us warm to cold gradients.

Look at all these good photos: all contains warm and cold areas. Even at noon, you’ll find them.

Why it’s important? Because this way you see better the volumes, the light directions. Even if you plan to make a final result very cold, warm or stylized in any way: start by finding a 50/50 balance, then go to what you want. A good balance of colors helps to find the magic point where the image feels right.

Also never use 100% black or white colors. Stay between values 0.2 – 0.8 (in a scale of 0 to 1) and 50 – 205 (scale from 0 to 255 RGB). Extreme levels don’t exist in nature, with a few exceptions in flowers, some birds, amphibians, and man-made materials. Don’t worry if the render looks a little too dark in the highlights. Its much easier and faster to correct the curves in the post process. Consider a render like a 80/90% finished process, like a RAW photography you treat after and reveal it.

3 ways to do use natural colors:
1) Use data. Every light source have a numeric value in different ways. Kelvin, nanometers, RGB. But where find the right colors of things? A clear blue sky, a fluorescent bulb? In kelvin temperature with the Blackbody node? No! Why? Because for example the moon has a red color in kelvin. Or we don’t see the moon red.
Kelvins values are not the human eye perceived colors, so it’s useless. Maybe someday we’ll have a node containing color charts under various circumstances.
Today, use this: a color chart by Jeremy Birn. Notice that he have 2 colors for each case, one for indoor and one for outdoor.


There are the RGB values that can be used in Blender. Make your own node group with every of these values and then you can connect what you need to your lights. I don’t stick ultra precisely on these values, sometimes I use 3380 k tungsten lamp for a sky that feel too clod in my scene. Try 2 lamps on a simple scene: 1 main slightly warm for the sun and another cold for the sky. Notice how even a subtle difference have a huge impact on the “right feel”.
If you want more science, read (or try to and then go drink a beer) this article on CIE illuminants. In the middle, there is a similar list of references.

2) Use photographic references (read point 10 below), or the picture inside wich you compose your 3D scene or object. Load an image into Blender and choose the color you want with the color picker, that’s it. To make it real, use real colors. You like this green foliage? Pick-it. You like this grey-blue overcast sky, pick-it. Simple as “Say hello to my little friend”, a well-known phrase in all bedrooms… Or in a famous Pacino movie.

3) Use your own taste, observation and sensibility. More risky for a look that match real world, but remember that a picture IS’NT AND WILL NEVER BE the reality. Professional photographers teach that. A photo is a representation of the reality, so forget the real thing, don’t try to replicate exactly. Even if you get to the absolute match between the reality and your render, it’s still feel wrong. Because a volume scene coming through your eyes is not like pixels coming through your eyes. So make your mourning, cry over pure realism, accept that fact and keep moving.
A picture, painting and a 3D render will feel real in a certain way of its own. What’s real for an RGB picture is not exactly what’s real for what you see looking on the real scenery. So we have to trick a little, to push here and there many small details that brings a flat image to a feeling of reality. In fact, that’s the beauty of every art form: it’s not real but in a strange way, it feel sometime real even if we know that’s not real.

9 – Optimize objects

Bevel all objects, even if its only a small flat face of 1 segment appearing 1 1/2 pixel in the render making a small line on an edge. Almost nothing is sharp in the real world. Use the Bevel Modifier, make this small rounded edges to catch a slim light line on corners. Small details make big picture.
Group objects together, don’t let loose parts wandering when you move the main body part.
Make thick enough walls. Too thick is often better than too thin. Make your object from your observations. What thickness is a glass bottle? Watch a bottle of glass.
– Distribute well the detailed and non-detailed parts of an object. Real object have some big flat planes without any surface or any volume in it, and some part are full of small details. The way of these two zones are distributed helps the sense of the feel right. For example, observe a machine in some factory. There’s come parts with only flat panels with tiny holes in the corners (screws) and some parts are made of corners, angles, buttons panels, tubes, etc. Look how these areas are distributed on the machine and you learn how to create a fake object that feels right.

10 – Collect references

It seems obvious but if you forget it, you don’t have anything to backup your perception. I often see “realistic renders” tutorials (even from the people who make great renders) without any concrete material from the real world to validate their work. It’s true that we can have a feeling of what’s real or not, but without photography, we cannot think of all subtle things that makes reality. Real light behavior is far too complex and rich. Use photography to learn what is real and help you to build something great. Stop thinking that you know what is the reality, be humble, look and search, it makes the job better and you smarter.

Search only for good photos made by professional or good amateur photographers. Forget all the others. Why? because only well processed photos gives you the right colors and tones. Colors that matches the real colors. Poorly processed images will give you only wrong colors. Stay away from it if you want precision.
For interiors scenes, look for architectural photos, they’re great example of how light works in the real world. For example here’s a nice house in  Switzerland but look the photos: all highlights are burned out. No details in it. The color temperature seems good but it lacks values in lights. Not perfect but still useful to learn light/shadows behavior.
CoeLux_OfficeHere an amazing new luminaire technology with nice picture with all in it to learn. look almost like CG. It’s not real sunlight but its a nice look.
For landscape renders, look at the great landscape photographers today. Inspire yourself from the great artists. That way humanity is growing, because we all climb on the giant’s shoulders.

For an exercise: choose a picture that you can reproduce fairly easely (without spending 1 month on it) and make the best render possible to make it match the photo. Then you have an idea how to build scenes that looks real.  To build up reality, mimic reality. If you have to make something totaly non-real (UFO’s, alien skin and so on), you have to search around, find materials that share some common aspects.


 Other things of my own:

11 – Build good shaders

I don’t have time now to detail this but do yourself a favor and learn from Cynicat pro. It’s a major step to get closer to real materials. Watch all the videos and you get smarter than before: Blender Physically Based Shading by Cynicat Pro.
He explains how he came to his shaders. It’s brilliant. With this knowledge you can make your own group of shaders and then your renders will instantly feel much better. I cannot thank him enough for what he did for the Blender community.

12 – Create realistic textures

This is also a primordial part of the job. A good exercise: copy a real scenery near your place. Take this plateform shed:
EIO_model

Now take pictures of every surfaces, concrete, asphalt, tags, wood walls, roof tiles if possible. Build the same model, apply the textures on the right places, and you get this:

EIO_test_hangar_render_scene_sunshine_3

 This feels right? Yes. It’s not because of the artist behind the monitor (maybe a little part), but mainly because of the textures. The light is fairly simple: 1 main sun lamp with soft shadows and cold color; 1 large area lamp for the overcast sky; 1 area lamp under the roof to accentuate de bouncing light from the floor. When you have the right shapes, patterns and colors, all sounds correct.

When time comes to create something without a model, use textures from other similar surfaces and adapt them to your needs. The time spend on Photoshop assembling these textures is worth the stretch. When you apply a photographic texture on a CG model, it comes alive right away.
And if you create a totaly out of ordinary scene, like I wrote above, that’s harder. You have to imagine the materials, the technology, what can feel real while beeing strange. Stick the the real feel.

12 – Create a base file containing your basic materials and lights

When you learn, you try many things to know the tool. You can just copy or download other’s nodes and materials but you will not learn how to do it. Playing with nodes is the part of the fun right? Doing it yourself is the main part of the process, so don’t download anything, make it yourself.
Create a basic scene, with simple volumes but with a few details, add lights with really good colors (think about cold/warm, reproduce a photo that you like wihout all details, just the simplified version of it): sun, sky, ground, some walls, good materials with physically based shaders. Make a few control renders until you’re satisfied with it. Once you have a good base scene, save it as the Startup file (File/Save startup File or Ctrl + U). Dont’ forget to backup the .blend file in another place for safety.

The purpose of it is to have a starting point with already all the basics materials and lamps that will become a more complex and final project.

So now you can start any project with all the basics already there. CG is a loooong enough process to avoid to rebuild shaders and lights every time. Don’t worry, you will move around nodes because every project needs special tuning to be right. The basic scene is a good starting point, then you elaborate from it.

13 – Evaluate and refine every aspects of your scene for each project

Fine tuning
20% of time goes to build the complete scene, and 80% to refine all details (very rough estimation by myself). It seems huge right? Imagine 2 days for the finished scene and 8 for refinements? Once you start to go to the realistic look, you realize that all is about details, and details takes time, period. Refinements in this small shadow, this color, this light position, this object thickness, this texture tone, this trajectory curve, and so on and on and on. It’s along process, but it worth the time and effort. It’s the way to get close to this feeling of reality. How do you think the masters achieve their great work? By working on it.

Constant evaluation
Matching a reality that is so rich and complex demands to observe, build, correct, observe, refine, evaluate at each step. Constant evaluation is the key. Is this color the good one? Is this the right way for this shadow? What did I miss? What sounds wrong in the scene? Don’t scratch your head loosing yourself in wrong beliefs or don’t get mad with yourself, just watch quietly your work.
Sounds self-mutilation? No! It’s the way of the job. It’s like this that we learn and grow, asking ourselves what’s going on. Every professional in every job tells the same thing: you have to do the job the best you can. Do it and enjoy the process, because it’s an adventure to find the golden city in the jungle. The pleasure is in the making, like “the life is the path, not the goal”. You feel much more satisfaction after working hard the right way (right = finding what’s works), and you get much better result. The artisan is always recognized as the master of it’s work, not the guy who push the button in a factory.

Know when to stop
When you work on your computer hours and days, it can be stressing. Stop a while, relax, make yourself a sandwich or a salad, a drink, watch the world (you know, the real one) outside your window, talk to people, go for a walk in the green, do some sport, take a bath (with candles and some nice music or an HBO special of George Carlin) then go back to your scene and watch it with a less noisy mind. You’ll be surprised sometimes how much we blinds ourselves in our head, stucked in what we don’t see when we stay long on a single job. Taking a rest once a while is more efficient on the long run and better for health.

14 – Render passes and recompose later

Only this way you can controls your refinements. A render is (a good) raw material. It’s not the final result, then you finish it in compositor or your photo software.
Younger, I tried really hard to make the best render possible, outside any photoshopping afterwards. And it was painful and useless. The time I spend on the render to look like the final result was much greater than the few minutes in composition. Doing all in the render is really tough. It’s just a matter of being a purist. And purist often get stuck in their limitations. Be flexible, find the right way to get the best result without limiting yourself in a system of belief.


About the famous Pixar’s Renderman.
Pixar’s render engine Renderman is available for free (non-comercial use) as an addon for Blender! Jeeze it’s Christmas! Registration needed. And patience, because before activate the Blender addon, you need to download the installer and wait until it downloads the 500 Mb to 1 Gb of data (!)
From I saw of it, it’s very flexible and rich. It uses for example a simple huge node for material with plenty of options in it. But, I must say that it’s not the orgasmic renderer either. You must work your scene, lights and materials to get a nice image. So nothing magic here. Did you saw some youtube tutorials made with Maya? Some people made crappy images with the most used soft in the industry, so… If you are accustomed to Cycles and know it well enough to build nice layered shaders and put lights in the right place, stick with Blender Cycles.

In my view, Cycles works pretty well, so I like to stay loyal to the free software. Most of the time, its the artist’s eyes that makes the difference. With the good-enough tool, you can get the job done.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s