Synthetic images, as we are calculating with Blender, are rendered with different types of algorithms; results vary the final representation of the objects in the scene.
We must distinguish between two different aspects when it comes to study in detail the process of image creation, from the point of view of the computer program that we use or we are programming, and that leads us to structure in computational techniques or methods.
From the point of view of a user, these notions allow us to understand the options afforded us a program and anticipate the effect thereof.
From a point of view of application programming your understanding is essential for its proper implementation.
- With respect to the idealization of the problem
- Methods based on image space
- Paths of x-ray techniques.
- Regarding the ways of programming
- Classical algorithms incorporated in programs
- Modern shading languages, that can be compiled independently.
The representation of a surface can be performed by projecting the surface on a projection plane or ray tracing and analyzing intersecting the collision of these rays with the elements of the scene. This allows us to propose two types of working methods:
We distinguish between the model of idealization and implementation as algorithms, programs languages and.
As always, we will do a first visual approach to the concepts; We will subsequently develop them by applying them to case studies with blender as a synthesized image generation tool and finally we will see practical calculation models.
The initial objective therefore is to get accustomed us to a new vocabulary (typical of these themes) In addition to creating a at the same time expectations that stimulate our creativity.
The first step is to see some examples to analyze differences that occur in images, as a technique that us close to the concept of “Shading”.
Suppose we have a simple model as a head consisting of a small number of polygons. (We will use the “Monkey” having how primitive blender)
We have added material to the object, in which you can define the same color. We will also indicate that surfaces softened to give it a more realistic look. The lighting and the background must be the same to better appreciate the differences.
What will we change then? Simply shading model. This is normally set associated with a concrete material, so the final image, If it contains multiple objects, It can be formed due to multiple “lighting models”.
Particularly in Blender is important n previously defined a material for the object and, then, Select the tab rendering algorithm “Shader” in mode of editing of materials.
The algorithm may affect the lighting in general, and particularly in the specular light, being able to perform different combinations depending on the effect that you want to get.
In the following examples the difference between one or another algorithm applied. The model used is specified in each one of the images and if at the same time, If the object is light emitter (autoiluminado)
Lambert
It is the classic model of lighting, In addition didactically as a reference used in the study of shaders or Shaders. It can be implemented both at the level of basic as with shading languages programming, being the most simple of all models.
It provides the basic ideas of diffuse lighting to the object.
The first model has a more dark colour clearly determining the used lighting (see glitters)
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Lambert
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Fresnel
The amount of diffuse reflected light depends on the angle of incidence of the light. The surfaces facing the light are dimmed, surfaces that are perpendicular to the direction of illumination therefore appear brighter.
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| Fresnel Emit |
Minnaert
It uses the model of “Lambert” como en los sombreados más básicos matizando la zona de brillo, obscureciendo el centro o aclarando los bordes.
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| Minnaert Emit |
Oren – Nayar
Implementa un modelo de iluminación que tiene en cuenta el comportamiento microscópico de la rugosidad del material.
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| Oren Emit |
Cartoon
Es un renderizado no realista, en el que se usan pocos colores con fronteras entre la luz y la sombra muy definidas. Su aplicación en dibujos animados es común.
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| Toon Emit |
Una interesante página explicativa de cada uno de estos modos de sombreado se encuentra en la documentación de Blender: Diffuse Shaders
