1 3D –graphics and animation Shading and Surface Characteristics Harri Airaksinen

2 Shading and surface normals  Shading = the moment in the rendering process when visible surfaces are assigned a shading value  Shading is depend on object surface and lights  Calculating the surface reflection is done by using surface normals  Common surface shading techniques include : faceted smooth specular shading

3 Faceted Shading (polygonal shading, tai constant value faceted shading )  Simplest and fastest – one shading value located in the middle of the polygon, direction is surface normal. Value tells how much light is received at the center of the polygon only. (how light it is)  take into account parameters of ambient light only (some diffuse)  do not handle complex surface characteristics such as texture and transparency well or not at all

4 Smooth Shading (Gouraud shading, intensity interpolation shading )  continuous shading value; blends throughout the visible polygons on the surface -> idea: to average the surface normals of adjacent polygons, creating a smooth transition of shading between polygons : sampling the amount of light reaching the surface normals in the center of polygons creating a vertex normal, averages the values of the surface normals of adjacent polygons blending the intensifies of the vertex normals in a polygon  No reflective surfaces and only surfaces with a matte finish.  take into account ambient and diffuse lighting parameters, and handle some of the complex surface characteristics well.

5 Specular Shading (normal vector interpolation shading,Phong, Blinn, Cook)  Mirror –like shading  calculates the shading at every point on the surface of a polygon  done by interpolating the vertex normals, and shading every point on the surface of the polygon by computing the relation between the angle of its normal and the angle of the incident light  can handle ambient, diffuse, and specular lighting, and detailed surface characteristics extremely well

6 Surface Shader  Material editor  tool for simulating materials  The shaders includes: reflectivity color texture transparency

7 Material Editor and 3D Studio Max Double-click Drag&Drop

8 Surface libraries or material databases Differences between applications

9 Surface Layers by adding layers and compounding their effects to determine the final look of the surface Makes it possible to build complex surface materials

10 Image mapping  2D image and mapping it on the surface of a three-dimensional object by projecting or wrapping  Very efficiently simulate not only the texture of a three-dimensional surface, but also other surface attributes such as reflectivity, transparency, and roughness

11 Image mapping  Images maps can modulate the surface characteristics by linking the brightness or color of a pixel in the image map to the characteristics of the point in the surface where that pixel is mapped -> the brightness of a pixel in an image map can control the reflectivity of the point on the surface where the pixel is mapped, or its color, or its transparency.

12 Creating the Map  2D -images that can be mapped onto 3D - surfaces: painted images photographic images abstract patterns (rule-based)  Input devices: recording a live image with a digital camera scanning an existing photograph painting with a flatbed laser digital scanner image libraries (software vendors, net …)

13 Own image maps and 3D Studio Max Double_click Drag & Drop

14 Projection Methods How the picture/ pattern is projected over the 3D object? Modifier  UV-mapping

15 Projection Methods  Most useful projection methods include: The flat projection method (planar) applies maps onto surfaces in a flat way - identical results as long as the three-dimensional surface is parallel to the projection plane The cubical projection method (box) is a variation of the flat projection method that repeats the map on each of the six sides of a cube - effective with cubes but only as long as one of the planes of the cube is parallel to the projection plane The cylindrical projection method applies maps onto surfaces by wrapping the sides of the map around the shape until the two ends of the map meet behind the object – bottom & top problem The spherical projection applies a rectangular map by wrapping it around a surface until the opposite sides meet, and then pinching it at the top and bottom and stretching it until the entire object is covered

16 Projection Methods - wrapping -  Textures to be projected onto 3D objects in a straight way, but also be stretched until the four sides of the map are pressed against each other

17 Positioning the Map - local coordination -  Not use XY –coordination, but surface local coordination system, U, V, W  U = horizontal, V = Vertical  Offset control how the picture is located on the surface, example and 0.5 locate the picture in half way in both directionn

18 Positioning the Map  Tiling  Map Blending = mixing images Using tiling: 3 times U- and V- axels.

19 Image map as a mask - Blending with matting techniques - Using ALPHA –image to mask holes to object surface Alpha –channel use: a CREYSCALE image file a that is linked to an image map saved with an image file in the form of a fourth channel in a RGB image determine degree of blending of the image map with a surface based on the intensity of brightness values of the pixels  file used=alpha channels

20 Surface Reflectivity  The basic three types of surface reflectivity are: ambient diffuse specular  Surface reflectivity types: Matte surfaces can be simulated by using a combination of ambient and diffuse reflections. Metallic surfaces can be simulated with ambient and specular reflections. Plastic surfaces are typically simulated with a combination of ambient, diffuse, and specular reflections

21 Environment Maps  They are special type of reflection map because they reflect not only the objects surrounding the mapped object, but also the environment surrounding the reflective surfaces  Environment maps can be animated: if something happened around the object, the movement is reflected to the object surface

22 Environment Maps  Spherical environment mapping

23 Environment Maps  Cubical environment mapping

24 Environment Maps – 3D Studio Max Rendering  Environment 2-click

25 Environment Maps – 3D Studio Max Render

26 Surface textures  Texturing techniques can be grouped : Visual textures are flat simulations of 3D -texture and no affect the geometrical surface of the object; they look textured but they are not. Example, a visual texture bricks is like brick wallpaper, and different from a real wall of bricks with relief textures that can be felt by touch. A benefit of using visual textures is make possible the creation of complex and rich textures with a minimal investment of polygons. Like color and procedural maps, environment, bump, and transparency maps Spatial textures exist in 3D and affect the spatial integrity of the smooth surface of an object.

27 Bump Maps  1978, developed by James Blinn  Simulates the bumps or wrinkles in a surface without the need for geometric modifications to the model  The surface normal of a given surface is perturbed according to a bump map. The perturbed normal is then used instead of the original normal when shading the surface using the Lambertian technique

28 Displacement Maps  Provide a unique way to use an image map to actually modify not only the shading but also the geometry of the surface being mapped  Displacement maps are often used to create 3D terrain. Terrains can be built with displacement maps that are based on photographic images of aerial views where the different elevations are coded with different colors or shades of gray.

29 Three-Dimensional Procedural Texture Maps  Solid textures  if you cut the object, cutline is presented in “correct” way  Rules control texture creation

30 Transparency  Surface feature  how the light penetrate the object  Can be faked or using ray tracing and real materials  transparency map  consists of a monochromatic 2D - image that is applied to a 3D -surface with the purpose of making all or some of the surface transparent

31 Controlling environment- dependent variables  Antialiasing – When the spatial resolution of an image is too low, its details are often lost

32 Controlling environment- dependent variables  Fast movement  Motion Blur  Needed feature when animation include fast object movements  not a default setup  Usually speeds of 1/250th of a second are necessary to freeze fast-moving objects.  30 fps (frame per sec = 1/30 seconds per picture)

33 Controlling environment- dependent variables  Fog  system add white color or transparency based on object and camera distance - depth-fading  Needed feature  not a default setup