This is an article I wrote several years ago that I plan to revise soon, so in the interests of posterity, here it is again before I work on it.
Photorealism : ( Fo-to-reel-isum)
the art of making an image look like a photograph. That should be all the definition we need, and it’s how we’re going to work with the term.
It’s entirely possible to render surreal items or bizarre angles and make them look very real.
For example, the kitchen scenes in fight club, or the opening sequence of Panic Room.
But the problem is unless people can easily see what has been done is real, it makes them think about it. This leads to looking for faults. A photo-realistic 3d piece will simply be taken as a photo.
Because you’re using a computer, and not paint, there is a more complicated element to the painting of your scene. The lighting, materials and models all need to be designed with your final shot in mind.
Do you need to model a section completely flat to fake a hard spotlight?
do you need to model an unusual shape to simulate bright light blurring an object?
Remember this when starting out :
A photograph is a captured moment in time. You should begin by planning the answers to two questions:
1. What will the viewer see?
2. What will they feel?
Your lighting and camera angle can have an enormous impact on emotional response.
An empty bedroom for example :
Interior Design magazine - Warm, inviting and cosy
Cinema shot after someone has passed away - cold, empty and lonely.
These could be the same room, identical in every way, but how its shown and where its seen from will change the viewers perception.
The main factors we will cover are:
Modelling Lighting Texture Rendering/post processing
And the order you should approach it.
Plan, Model, Light, Texture, Render, Process
This tutorial covers the basics of each of these points, and information essential to producing a photorealistic image.
One of the most overlooked things in 3d modelling is construction. By construction I mean how an item/object is constructed.
It’s far too easy to make things out of a single object and to forget that in the real world, things have seams, edges, cuts, marks and other indicators of how it’s made.
Our example item for modelling is a microwave.
Simple enough, it’s shaped like a box, how complex could it be.
This is where your goal of photorealism starts to come into play.
A microwave is made of panels, there are vents, inside those vents you can see the inner workings, there are joins, hinges, rounded edges, thick edges, thin edges, layers.
The door for instance could be modelled as a single flat piece. But the edges have thickness, rounding, the window in the door is layers thick, with mesh, Perspex, seams.
The clock is a backlit LCD; there are layers of the LCD, a shell to contain it, a space between the clock and the front panel.
When modelling your object, think about how it was assembled, is it one piece, are there seams, panels, screws, bolts, nails etc.
Do not leave 90 degree edges, as far as normality is concerned they do not appear
I am aware there are straight edges in reality, and they do look unusual when you see them.
Chamfer edges, place imperfections on your edges, consider the age of your object when modelling.
The older an item is the more wear and tear will need to be physically modelled in. Bent edges, dents and broken pieces all form a part of the modelling process.
NB The displacement possible in some rendering systems can all but eliminate the need to model surface detail, but remember displacement is done along the normal of the polygon, so edges still need to be chamfered.
Lighting is one of the most difficult aspects of photorealistic rendering.
Lighting in your scene serves two purposes. To tell the story of what is happening and to simulate reality.
The reality part we’ll cover in a moment.
Every light in your scene MUST serve a purpose.
Changing the position and brightness of a light will affect the mood of a scene.
Dark lighting from behind or smooth even lighting from in front will help to portray your scene.
Think of how lighting is used in an interrogation scene from your favourite movie. The bright light on the subject and the detectives moving in the darkness brings more emotion into the scene. This is more than just simulating what happens in real life, it’s about emoting the scene.
The subject in bright light shows them as the focus, the centre. While the others moving in the dark seem mysterious, powerful, evil.
Use lighting in your scene to bring emotion to objects and places.
Simulating reality:
Light bounces. All light, all the time will be reflected off a surface.
Light is not unidirectional. There are very few circumstances where a scene or an object is lit from a single direction. More often than not there are multiple light sources as well as indirect light.
Light is coloured. Light bulbs, the sun, the sky, a candle, none of these produce pure white light.
The basics of lighting will require you to use an advanced lighting system. Light needs to bounce realistically. You simply cannot fake this by hand. You can use a skylight script for soft shadows, but an intricate shape, scene etc will not look real with a skylight, absorption, colour bleeding, bouncing light etc all occur and need to be simulated or faked.
The important step is not to let the computer do the work for you, it won’t look real. Set parameters correctly, move lights into the correct position.
Lighting includes shadow work. Shadows indicate the 3 dimensional nature of an object. Shadow density also indicates the relative reflective properties of a surface and its geometric position in relation to a light source.
Key tips:
Tint your lights or use blurry images as projection maps.
Turn shadows off on your lights except one “main” light source.
Use falloff on your lights. Even a lighthouse fades at a distance.
Use omnis to simulate bounced light in some areas. Your rendering system will bounce light equally off all surfaces. Instead of attempting to modify material properties, throw some light in where it should be.
This lighting example is a very quick demonstration of coloured light, shadows and variety can add depth to an image. Examples 3 and 4 use either noise or a photograph as the source of light. These subtle variances from one point to another can help bring another level of realism into your image.
The downfall of many otherwise brilliant renders.
Textures and/or materials form the surface and depth of your scene. They indicate how a surface looks, feels and even what’s happening under its surface.
You need to consider how a surface looks. The problem is that 3d software is not arranged the same way as your mind. You know what fabric looks like, and by looking you can tell velvet from satin, but WHY does velvet look different than satin?
There’s its colouring first, the pattern on your lounge suite, the orange of an orange.
Then things get complicated.
Texture, is it rough, smooth, made of millions of tiny lines, or scratched and buffed. This will normally be your bump map.
How does light bounce, reflect or play across the surface? Is it absorbed like skin or wax, or does it reflect bluntly like steel.
Ideally work with every feature of a material except colour.
Set the diffuse channel/colour to medium grey. (128,128,128)
Cloth should look like cloth, wood look like wood, if it doesn’t look the part grey, then you’re modelling or lighting isn’t completed.
Texturing notes: Imperfection is king, reality is seldom perfect, edges don’t always match up, patterns don’t flow seamlessly, paint doesn’t go on evenly. Consider the texture/colour/glossiness etc while working on each of the others.
Has colour faded where it’s exposed to the sun? Was the object painted a different colour at one stage?
You can also double back into your modelling at this point. Model a fleck of paint peeling off and texture in the colour underneath to help with the impression of age.
This is where it starts to shine through, the step where you get to correct for and make use of the other steps along the way.
NB: This section of rendering technically comes before everything else, as your final render angle dictates modelling detail, texture, etc
Firstly choose a camera angle and lens size, what are you trying to show, how should the shot line up. Use the same ideas you would for a normal photograph. Is an object half into the scene, can you see emptiness where another room should be etc.
Rendering and post processing will vary greatly between 3d applications; however some features will remain the same.
Blur/Depth of field: not everything in your image will be in focus, you simply cannot have everything from here to infinity in focus at the same time, and you can cheat and place a wall behind your shot, so everything from here to there is in focus. Each shot will decide if blurring is minimal in the background or extreme DOF to show off a product render.
Bloom: The spreading of light, the effect of how your retinas or a film reacts to a bright area. The lightness “bleeds” and expands, giving a soft haze or halo over a larger area. This is one of the easier touches to bring the rendered image closer to a photograph.
Colour correction: RGB monitors and film do not display colour in the same way, to get closer to a final print style, I normally desaturate the image with a gradient. Left to right, or angle it to match dark and light areas. Not a lot, 3-10% maximum from one extreme to the other, but it looks more natural than a direct render from a lighting plug-in.
Noise: If the image wasn’t created on the computer, and it arrived via a camera or scanner, each of these will bring micro errors, tiny bits of noise imperfections etc. Apply noiseor scratches on another layer in your image editing application; adjust the blending mode and opacity to give a subtle break-up of pixels.
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