ARTICLES: Non-Photorealistic rendering (NPR)

First of all, let’s talk about Photorealistic Rendering (PR)

Computer Graphics (CG) has a target: Reach realism in images and animations render. This concept is called Photorealistic Rendering or PR. The render, composition, texture, materials and models quality that several artists reached nowadays can, easily, confuse our perception.

Autodesk has created a website called “Fake or Foto” where we are invited to see some pictures and to respond if that picture is a computer graphics result or a real photograph. Test yourself here . My score was 55%.

One of my favorite artists in Blender community is Andrew Price. He is the founder of the BlenderGuru.com website. He has reached an amazing level of quality and he is one of the best artists in Photo-realism Rendering! See some examples:

andrew-price-bathroom-whole2 Japanese bathroom by Andrew Price
Font: BlenderGuru.com

 andrew-price-lounge-whole Lounge by Andrew Price
Font: BlenderGuru.com

 

andrew-price-oakville-wide
Oakville by Andrew Price
Font: BlenderGuru.com

This is definitely the state of art in Photo-realistic rendering. I suggest you to follow Andrew’s website. There is a lot of tutorials and he is a great teacher.

Now: Non-Photorealistic Rendering (NPR)

According to VILANOVA, Non-Photorealistic rendering (NPR) is the creation of images that are not and do not want to be realistic. According to her, there are several motivations for this application:

  • Artistic motivation: Express feelings, attitudes, expressions impossible to be transmitted through photo realism and, of course, much more …
  • Understanding and clarityDrawings and illustrations that are manual or look like hand-made material are often used in manuals to technically inform the functionality of an equipment. These drawings show what is essential and the user does not get lost in unavoidable detail in photographs of the same equipment.
  • Aesthetic: Often, NPR can be used to show the aesthetics of an environment, a combination of items, without worrying about the actual appearance of the objects, or even where the actual appearance is avoided when it is not the focus of the product.

There are some NPR categories that we would like to define for this website. In his article, PENNING defines five categories that, I believe, are more than adequate for us to follow on all materials for this website.

NPR categories according to PFENNING:

  • Pen-and-Ink illustration
  • Painterly rendering
  • Cartoons
  • Technical illustrations
  • Scientific visualization
So, let’s make it clear that we are not looking for one of the categories, but we will try, as much as possible, to include materials, tutorials, documentation on all of them. Although the site name is “BlenderToon”, we do not want to be focused on the Cartoon category, neither the low poly techniques (in current trends), but we will talk about these, too.
Whatever your motivation to move forward with NPR is, we would like to help you with the information you need to move forward and grow. So, please, always participate, comment and leave your suggestions.

Now, let’s try to describe the NPR categories:

  1. Pen-and-Ink illustration
This is literally the creation of images similar to the illustrations created with pen and ink.
In this type of illustrations, some techniques are used. PFENNING points out the following techniques:
  • Cross-stitched
  • Contour
  • Line Art
This category has some important elements and we will use the concepts presented by VILANOVA:
  • Strokes
  • Tone
  • Texture
  • Contourn
  • Indication

One example of this category is:

pen_and_ink Font: VILANOVA

  1. Painterly rendering

In this type of rendering, the goal is to represent what painters achieve on their canvases. Painting styles guide CG artists in this category: Impressionism, Expressionism, etc …

One example of this category is:

painting
Font: VILANOVA

  1. Cartoon

This is probably the best-known category of NPR. Our site has your name because of this category. Most of the cartoons are from this category. In this category, one looks for the color, the exaggeration, the distortion, often solid colors.

One example of this category is:

CARTOON

  1. Technical illustrations & Scientific visualizations

In this category, we present scientific and / or technical information by illustrating important properties of the presented object. Excluding any unnecessary detail for the purpose for which the image was created. According to PFENNING, there are four conventions for this category:

  • Lines must be black (edge lines)
  • The colors used should follow a cold color scale for warm colors
  • Only one light source should be used.
  • Shadows are rarely used

One example of this category is:

TECHNICAL
Fonte: VILANOVA

The site BlenderToon aims to include information on the five categories. We hope this short article has set some important things about NPR and that we can continue together on this journey.

Leave your comment, your review and suggestion.

Leo BlenderToon!


References

PFENNING, Frank. Non-Photorealistic Rendering. 15-462 Computer Graphics I, Lecture 22. Disponível em <http://www.cs.cmu.edu/~fp/courses/graphics/>. Acesso em 07-Agosto-2017.

VILANOVA, Anna.  Non-Photorealistic Rendering. Disponível em <https://www.researchgate.net/profile/Amy_Gooch/publication/220695277_Non-photorealistic_rendering/links/0deec51b60866b7afd000000.pdf> Acesso em 07-Agosto-2017

WIKIPEDIA. Non-photorealistic rendering. Disponível em https://en.wikipedia.org/wiki/Non-photorealistic_rendering . Acesso em 07-Agosto-2017

HERTZMANN, Aaron. Introduction to 3D Non-Photorealistic Rendering: Silhouettes and outlines. Media Research Laboratory, Department of Computer Science – University of New York. Disponível em: <http://www.mrl.nyu.edu/publications/npr-course1999/hertzmann-intro3d.pdf>.  Acesso em 07-Agosto-2017

 

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