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Introduction to the creation of photorealistic synthetic images





1.      Imitation of natural perspective in photorealistic tridimensional representations.

The gretest artists of the italian Renaissance were among the first ones to focus on the use of special tecniques that could be deceptive for humans eyes, by simulating depth on bidimensional surfaces. This illusion is based on a whole of geometrical knowledges that dates far back to Greek civilizations.

Renaissance artist learned to turn these knowledges into works of arts which were characterized by an impressive realism. Up to the artists had been using art to represent ideas, Renaissance artist besides began to consider art as a particular device which could be used in order to simulate reality. That marked a huge fundamental changing.  

By this time, more than a century of cinema and photography has deeply explored the tridimensional space representation on straight surfaces. Movies mixing up animation and tridimensional images with photographic and cinematographic traditional tecniques led our attention towards a subject whose aim is to accuraty shape phisicaland optic proprieties of the real word.

Again, art and mathematics  joined together to charm and guide the observer into the unreal but sinthetic imaginary, allowing human mind to be able of a fantastic creation of the immaterial.

Photorealis describes images created by computers using phisical and optic proprieties of the real world, mathematically translated, so that an observer find himself deceived at the point that he experiences a hard time in telling an artificial image from a photograph.

The ability of the computer operator and of the computer itself in simulating photographics images particularly striknes all those persons thinking to computer just as aseptic instruments, exclusivelly mathematics, without any regard to their real potentiality on this topic; they can be considered as tools that could substituite brushes and palette of past artists.

Anyone having ever found himself in drawing a tridimensional form, certainly experienced difficulty while creating depht illusion on a stright surface. By the way, tridimensional space concept is likely to be so abstract that even children don’t have an innate comprehension of concepts like depth and volume themselves.  

Learning of objects shaping in the space is, in a way, so important that basic principles are often forgotten; even if not so much time haspassed since artits began to appreciate and exploit the potentialities.

Passage was almost istant : panel on the left shows a Cimabue work (1240-1302 , 1280 ); panel on the right a Giotto work ( 1266-1336, 1310 and than 30 years later ). We can see them placed together on the same wall at the Uffizi Gallery of Florence; though separated by a huge conceptual difference.



Cimabue was interested in tridimensional representation ( one can easily deduce that observing the form of the throne and arches below ), nevertheless it hasn’t obtained a realistic simulation: in fact, in a photograph it would’n be possibile appreciate, at the same time, the internal wall of all the three arches. Therefore it comes out the impossibility in finding a correct point where we could place our observation point; so, the painting itself, in its entire forms, is likely to seem unrealistic if to a well used to tridimensional eye observation.  

Within the thirty years passed from Cimabue fron Giotto works, artists has discovered a new powerfull method in order to guide the observer while comparing different paintings. Giotto painting is seen with a more relaxing sensation, thogh it isn’t perfect yet.  

It is necessary to wait till Renaissance (1450-1500) to gain mathematic codification of perspective and its correct graphic application.

Piero della Francesca ( Pala Urbinate – 1472 ), Giorgione, Leonardo da Vinci, Correggio and later on all subsequent artists considered perspective and tridimensional draw tecniques as a philosophical thought, where order of things is likely to coincide within the mathematics of the form and, therefore, an extract measure of the real world.

Escape point is clearly determinated, tridimensional solidities are conspicous, background is a lettle hazy, foreground is brighter and more contrasted, volumes and dimensionals are correct with regards of depth. 

These statements convince human eye to imagine a depth right where it can’t exist and the artistic collocation light up natural world to the same level of spiritual world typical of the religious content. Therefore, we can say : a perfect mathematic coordination between divine and earthy.  

Since technology takes place between artist and his work, it would be likely that one easily thinks that art is turning into something too mechanic, without any sort of inspiration. However, the Renaissence ‘happy matrimony’ of science, technology and art contradicts this hypothesis.  

To reach a clearer comprehension of the matter above an example follows: the well-known ‘Calice’ from Paolo Uccello ( 1465 ). It results composed of segments when subdividing the surface into rectangular geometric forms. These last seem to us definitely similar to polygons abtained with nowadays computerized images ( wireframe );
it is quite striking thinking that this happened six centuries before computer elaborations.


The 'Calice' of Paolo Uccello (1465)    Computerized elaboration of the 'Calice'


1.      Creation of synthetic images with the computer graphics.

At the beginning, computerized tridimensional images were created by means of mainframe computer using direct mathematic formulations. Currently, a lot of softwares allow us to manage complex graphics by means of a ‘frendly interface’, that simplifies access to several functionalities of program and makes objects elaborations, scene and lights much more openly intuitive.

Creations process can be schematized with the following 4 phases :


1.1   Planning

This is the creation of storyboard . One has to define the ideation of the scene just like an artist creates with a preliminary sketch, the work he is going to realize. In computerized elaborations storyboard is mainly usefull while planning the complexity and to obtain an overall approval before the productive process gets on the way.


1.2   Shaping

Shaping is the process of creation of objects geometry and assignation of surfaces to objects themselves. At the moment, many different tecnicques allow us to accelerate this kind of procedure that, otherwise, would be very complex: extrusion from 2D, interpolation, sculpting from 3D, procedural methodology, etc. with care of the program we are going to use. Therefore, 3D objects resulted from the work above can be composed of polygons in the space similar to an iron cage, or bidimensional surfaces in the space ( Bézier’s, spline,etc. ) or solid massive compounds i.e. with barycenter of masses.

In any case, a pixel surface is applied on these objects, using a reference map in different ways: assignation of a pictorial texture (winding), assignation of procedurale textures (fractal algorithms) or by simple shading ( color plus light ).  

1.3   Scene

The preparation of the scene is carried on with the tipicall way adopted for theater productions, i.e. with the collocation of objects within definite space, camera, equipping of lights and, eventually, animation actions ( frames ). The planning out of the scene can also place with the simoultaneous partecipation of an aesthetic evaluation of composition that will be, afterwards, the final resul on this elaboration 

1.4   Rendering

It is the operation for automatic conversion of objects and their attributes turned into one or more fit-to-print and file syntetic images. During this work-period, computerized systems make    plenty of calculation and even the most sofisticated computer  potentiality is put to a hard test. This is definitely the most complicated computer elaboration man has ever conceived and since
 just few years we are able to create synthetic images of great sophistication in moderately brief periods of time


Utah Teapot

(object of reference for comparison of the qualities of the algorithms)


1. Algorithms for 3D  visualization.

Light and shandings are the main parameters that define higher or lowel of photoreality in a scene. There are several methods for shading; they can be condensed as follows:

  ·     Wireframe  

Objects have diaphanous surfaces that allow us to see hidden lines and points. This method is exclusively geometric , not photorealistic, and permits a real-time visualization while moulding the scene.

  ·   Flat  

A single level of illumination is assigned to the entire polygonal surface of objects, so that single faces ( mesch ) show a uniform dull color and differents each others. This definition doesn’t produce so natural results, but it requires a little time for elaboration. It is mainly used for preview visualization.  

  ·  Gouround

The power of light is shed over the entire polygonal, allowing to fade side edges but, still, surface remains not continuous and little realistic if we don’t make use of other corretive algorithms. Calculation time is quite fast.  

·   Phong


This definition produce a surely more realistic result. Each pixel of the surface is calculated with regard of the luminous source by means of reflection effects. The number of necessary calculations is much greater if compared to previous method and it increases if the image resolution increase.


Commonly used standard algorithms are 3 :

·   Scanline

Where the color of a point of an object is determined through its relationship with the observer and with the luminous sources of the scene itself. Reflections, refractions and shades are not moulded.

·   Ray-tracing

Each pixel of the object is calculated on the basis of the whole light involving it ( reflected one included ) by tracing luminous ray path from a point of the screen to all the objects of the scene and, afterwards, to the luminous source. Reflections, refractions and shades are moulded.

·   Radiosity 

All the object iterations, lights and screen are defined, including luminous rays not reaching the screen. This is the most precise modality but a so high calculation time ( few ours  ) restricts its usage just to great systems and for particular necessities.

·  'unbiased rendering'

with once of enough rendering ( to the endless one), the final render will always converge toward the correct solution without the introduction of artifices. The other motors of rendering or other methods of interpolation always produce ‘biased renders, they cannot independently guarantee consequently the convergence toward the correct solution from the planned computational time. This algorithm is what produces the most elevated quality and  is currently used by the most greater producers of CAD 3D professional (3dsMax, Viz, Maya, Lightwave, Rhino, Solidworks, ArchiCAD, Cinema 4D, Blender, etc.).


Photorealistic effects of reflection and shading of an algorithm of ray-tracing.

Which are the real photo and the images photorealistic created with an algorithm of radiosity ?


TILECAD  foresees the use of the following computational algorithms for the creation of images 3D:


-          OpenGL ( MESA ) : algorithm phong for the immediate calculation enriched with effects of shades

-          POV-Ray : procedures for the calculation in ray-tracing

-          MEGAPOV : enrichment for the calculation in radiosity

-          INDIGO : procedures ‘unbiased rendering


Each of these technologies has his specificities and characteristics and their use it is tightly in operation of the necessities of the consumer. we don't enter the complexity mathematics-physics to understand the conceptual differences among the single procedures but we appraise rather some parameters that qualify  the synthetic image final. The computational time (consequent also of the computational abilities of the computer system) it is certainly a parameter to consider with attention:

This diagram allows to appraise that having available a greater computational time they are always gotten greater quality to condition to change the typology of rendering. Opposite with low availabilities of time it is not worthwhile to use algorithms that require for them nature of strong potentialities of elaboration.The consumer has to appraise in advance the ‘s resources that you  intends to use and the availability of attended before getting the result. In operation of this decision can activate the consequent procedure. He could for instance reassume this way:

  • low computational abilities and immediate application: Phong

  • averages computational ability and application within some about ten minutes: Ray-tracing and/or Radiosity

  • tall computational abilities and application without limits of time: ‘Unbiased '



Example of render  with algorithm ‘unbiased' in an inside: to get the effect of external solar light that penetrates from the window and it radiates him in the environment and on the objects, reflecting itself and refracting itself, necessary 12 hours of elaboration have been with a workstation of averages ability.


TILECAD software links.

The program 2D/ 3D of plain’s composition TILECAD laying, you in his releases of distribution customize, it use Flat algorithms for the visualization in real time 3D, algorithms of Gouround and Phong, altered and adulterate, for the visualizations to average and tall definition.

POV-Ray, MEGAPOV e INDIGO  it foresees be algorithms of ray-tracing that of radiosity for the creation of synthetic images, as like other software of visulisation 3D.

I use it practically it of all the algorithms of visualization allows to the consumer of obtain levels of photorealism  to his discretion: from that simpler and foreseeable up to that more adulterate but with times of very tall elaboration.


Of succession see the general structure that we foresee for an I use optimal of these tools:


That the structure of the scene 3D has given birth to automatically from TILECAD, I for him use of software with algorithms of ray-tracing / radiosity, the consumer must stop particularly on the correction of the lights/ shades and on the procedural texture that such software allows.


In fact also if TILECAD inserts in the preparation of the line of conversion all the graphic information and you of visualization  that has been use that for the visualization to his inlan it is not said that it am sufficient for obtain synthetic optimal images, sight the modification of the used algorithms.


It is advised to read the documentation that we allege and of experiment directly with the present examples. Additionally seen the long times of calculus and the informatic weight of these modes consults:

Foresee systems hardware of elevated power.

 Creation of preliminary images to lower part number of pixels.

  Uses of the algorithm of alone radiosity like conclusive process.

Accurate control of the points light.

Attention to the effects of perspective that they could be deforming.

Uses procedural respect to the maps of  bits of the texture.

Threshold the complexity of the scene especially on the backgrounds.


For download POV-RAY
Licenze and terms and conditions of use - Persistence of Vison©

3D-Stereoscopic images (Anagliph)

The 3D-stereoscopic images are known from beyond 100 years and they am corporate beginning from 2 different superposed images in such way that each eye sees only ‘his’ image.

Because of the finite resolution of the monitor, the best manner for realize 3D-images on a computer it is that said of the ANAGLIPH: an image comes ‘encoded’ in red, the other in blue or green, after of that it is proceeded with the overlap.

For see (‘decipher’) the images are necessary of the special glasses with red and blue lenses (or red and green). Such glasses, realized in plastics or carton, they are very economic and  they could be acquired for few money.


TILECAD create the anagliph images  with a specific option to the inland of the program. An example of this elaboration is the inferior image. For preview it you bring the glasses to the eyes (the red lens must be to the left hand) and gather on the image. You should have the impression of a three-dimensional vision of the surrounding. A 10% of population of the world is not in degree of see three-dimensional images neither with this method neither with other more sophisticated (for a genetic limitation of the left part of the brain that checks the sight) we hope that you are not in this statistics.



6.   Visualization 'Sketch - no photorealistic render'  (hand drafting / cartoons)


After a long codifies and test has been produced completely from OMNI DATA a new algorithm of visualization 3D for TILECAD© of the type ' not-fotorealistic render - Sketch' and that he already adds to the 7 existing typologies.

Totally in automatic and immediate way, the procedure transforms the visualization 3D in a fac-similar of sketch ' hand drafting' / comic strip, in tonality of grey with sbording of the straight lines, loss of the colors on you furnish to him and outline of the images in transparency.


The result is saving  in one file or printable for the following elaborations that the user you can effect using very quickly or computerized programs of color-draw or the usual tools artistic manuals (ink, pencils, pieces of chalk, tempers up to the use of the aereograf). To drive the algorithm and to get the most consistent image to necessities, the user can choose between 3 typologies of impression of writing:

  • China Ink
  • Pencil
  • Charcoal pencil

also intervening on the choice of visualization of you furnish 3D to him and on the layings of the tiles. Some algorithms studied on purpose for this new visualization are also proposed in the typology ' Phong' to low quality.

To conclusion it is gotten totally practically an indistinguishable sketch from one appreciated production of impression manual and artistic losing so the computer connotation.