1. Non-photorealistic rendering
Marko Täht

2. Topics
Rendering
Photorealism
Non-photorealistic rendering

3. Rendering
Rendering is the process of generating an image from a 2D or 3D model by means of computer programs.
Multiple models are collectively called a scene file.
Scene file contains: geometry, viewpoint, texture, lighting and shading.
Data in scene files is passed to rendering program to be processed and output as digital image or raster graphics.
Rendering image from scene file is called graphics pipeline along rendering device.

4. Graphics pipeline
Graphics pipeline or rendering pipeline refers to sequence of steps in order to make 2D raster representation of a 3D scene.

6. Photorealism

9. Photorealism is a genre of art that encompasses painting, drawing and other graphic media, in which an artist studies a photograph and then attempts to reproduce the image as realistically as possible in another medium.

10. Clay-render
Final picture

11. “If photorealism is the holy grail of CG, then a photorealistic face
Face made in blender
“If photorealism is the holy grail
of CG, then a photorealistic face
must be the holy, HOLY grail.”

12. Non-photorealistic rendering
Non-photorealistic rendering (NPR) is an area of computer graphics that focuses on enabling a wide variety of expressive styles for digital art.
It is inspired by artistic styles.
In movies and video games NPR has appeared in form of “Toon shading”. Modern use of this is cel-shaded animation.

13. Paint brush

14. Technical drawings Photorealistic images not reasonable
Give better overview
Exploded view

17. Exploded view

18. Leonardo da
Vinci
Reciprocating
motion machine

19. Wireframe Only edges are drawn Used in making models
Visualizes the structure of object
Simple and fast to calculate
Often used when high- framerate is needed

22. Pen and ink Strokes - wavy lines of varying thickness
Texture - collection of strokes
Tone - lines of equal weight and spacing
Outlines – Boundary line of the structure to separate it from background

25. Watercolor
Suspension of pigment particles in water, binder and surfactant
Each stroke needs fluid simulation
Paper affects fluid flow

28. Toon shading Also known as cel-shading
Designed to make models look flat by using less shading color
The name comes from cels (short for celluloid), the clear sheets of acetate, which are painted on for use in traditional 2D animation.
Spongebob Squarepants season 4-8

31. Sobel filter Creates image emphasizing on edges.
It is a discrete differentiation operator, computing an approximation of the gradient of the image intensity function.
Operator is based on convolving the image with a small, separable, and integer-valued filter in the horizontal and vertical directions and is therefore relatively inexpensive in terms of computations.

33. Why not in real life

34. Games that use cel-shaderQ

35. Borderlands

36. Antichamber

37. The Simpsons Game

38. Creating cel-shader Vertex shader:
uniform vec3 lightDir; //Defined in world space
varying float intensity;
void main() {
intensity = dot(lightDir, gl_Normal);
gl_Position = ftransform(); }

39. Fragment shader: Sets the fragment color based on intensity
varying float intensity;
void main() {
vec4 color;
if (intensity > 0.95)
color = vec4(1.0, 0.5, 0.5, 1.0);
else if (intensity > 0.5)
color = vec4(0.6, 0.3, 0.3, 1.0);
else if (intensity > 0.25)
color = vec4(0.4, 0.2, 0.2, 1.0);
else
color = vec4(0.2, 0.1, 0.1, 1.0);
gl_FragColor = color; }

40. Result