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Game Programming 06 The Rendering Engine

Game Programming 06 The Rendering Engine. 2010 년 2 학기 디지털콘텐츠전공. Rendering in Video Games. Depth-Buffered Triangle Rasterization Virtual Scene Virtual Camera Various Light Sources Visual Properties. Solving the Rendering Equation (Shading Equation). Rendering in Video Games.

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Game Programming 06 The Rendering Engine

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  1. Game Programming 06The Rendering Engine 2010년 2학기 디지털콘텐츠전공

  2. Rendering in Video Games • Depth-Buffered Triangle Rasterization • Virtual Scene • Virtual Camera • Various Light Sources • Visual Properties • Solving the Rendering Equation (Shading Equation)

  3. Rendering in Video Games • Purpose of the rendering: • Photorealism • Stylized look (cartoon, sketch, watercolor and so on)

  4. Describing a Scene • Scene is composed of objects: • Opaque (solid) object • Surfaces (triangles) define its shape • Don’t care about inside • Transparent object

  5. Representing object (surface) • Surface: a two-dimensional sheet composed of an infinite number of points in 3D • Representation • Analytical form (parametric surface equation) • Collection of Patches • Triangle mesh

  6. Representing object (surface) • Analytical form (parametric surface equation) • Ex.) Sphere equation

  7. Representing object (surface) • Collection of Patches • Patch: a simple rectangular surfaces • Similar to a quilting • Ex.) NURBS, Bezier Surfaces, Subdivision Surface Quilt NURBS surface NURBS modeling

  8. Representing object (surface) • Triangle mesh • A piece-wise linear approximation to the surface Piece-wise linearapproximation to a function Piece-wise linearapproximation to a surface

  9. Representing object (surface) • Triangle mesh • Using a triangle because: • It is the simplest type of polygon • It is always planar • It still remains a triangle after transformations such as affine (projective) transformation • All graphics card support a hardware acceleration to draw it

  10. Triangle Mesh • Tessellation • A process of dividing a surface up into a collection of triangles • LOD (Level-of-detail)

  11. Triangle Mesh • Winding Order • How to define the front/back face direction • Counterclockwise (CCW) / Clockwise(CW) Counterclockwise winding order Computing normal direction

  12. Triangle Mesh • Representation of mesh • Triangle list : 점의 좌표

  13. Triangle Mesh • Representation of mesh • Indexed Triangle List : 점의 좌표 0 1 2 3 4 5 6 7 Vertex list: Indexed triangle list:

  14. Triangle Mesh • Other representation of mesh • Triangle strip • Triangle fan Vertex list: Triangle strip Triangle fan

  15. Model space • Positions of a triangle mesh’s vertices are usually specified relative to a local coordinate system. (front/left/up) up left front

  16. World space and mesh instance • Individual meshes are located in a scene (world) • Mesh instance: • Any one mesh might appear many times in a scene • Representation: • Reference mesh, and its transformation matrix red: model coord. black: world coord.

  17. Visual properties of a surface • Information needed to define a final color in the rendered image: • Direction of surface normal • Diffuse color • Shininess/reflectivity • Roughness • Texture • Opacity or transparency • Other optical properties : How light should interact with the surface

  18. Introduction to Light • What we see is a result of complex interactions of light with matter. • Four main interactions of light • Absorption • Reflection • Transmission / refraction (bent) • Diffraction

  19. Introduction to Light • Absorbed by a surface Why does red look red?

  20. Introduction to Light • Reflected by a surface

  21. Introduction to Light • Transmitted through a media • Partially absorbed or refracted

  22. Color model • Color model: how to represent a color • RGB (Red-Green-Blue): • RGB888 (8 bit for each channel: 0~255 integer) – 24 bit • RGB565 (5 bit for red, and blue, 6 bit for green) – 16 bit • HSV (Hue-Saturation-Value) • LDR (Low Dynamic Range) vs. HDR (High Dynamic Range) • HDR: RGB in a higher precision (float value)

  23. Color model • LDR with various exposes and tone mapping

  24. Alpha channel • Representing opacity • A fourth channel to RGB  RGBA or ARGB • RGBA8888 – 32 bit per pixel • RGBA5551 – 16 bit per pixel

  25. Vertex Attributes • Position vector (x, y, z) • Vertex normal (nx, ny, nz) • Diffuse color (dr, dg, db) • Specular color (sr, sg, sb) • Texture coordinates (u, v) • Skinning weights (w1, w2, …)

  26. Attribute interpolation • Flat shading and Gouraud shading Gouraud Shading: Inside color is interpolated from the vertex colors

  27. Texture maps • To overcome the per-vertex attribute, using image to fill-in the polygons

  28. Texture maps • To overcome the per-vertex attribute, using image to fill-in the polygons + =

  29. Texture maps • Texture coordinates: • 2D coordinate system defined on an image • Denoted as (u,v): uv-coordinate u u v v

  30. Types of textures • Types of textures • Diffuse map • Bump map • Normal map • Gloss map • Environment map

  31. Types of textures • Diffuse map • describing diffuse surface color

  32. Types of textures • Bump map (similarly displacement map) • Describes small perturbations in height A sphere without bump mapping (left). A bump map to be applied to the sphere (middle). The sphere with the bump map applied (right)

  33. Types of textures • Normal map: encodes normal vectors Low vs. high res. Low res. + diffuse map Low res. + diffuse + normal

  34. Types of textures • Gloss map (similarly specular map) • encoding how shiny a surface should be

  35. Types of textures • Environment map • containing a picture of surrounding environment for reflection

  36. Mipmapping • Different resolution of the texture with respect to the distance between an object and a camera

  37. OGRE::Mesh in action • Get the sample file at our home page • Create your own cylinder mesh from scratch.

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