Computer Graphics Seminar

Transcription

1 Computer Graphics Seminar MTAT Spring 2015 Raimond Tunnel

2 Conclusion

3 Geometry Point location in space Vector direction in space Polygons Simple vs non-simple Convex vs concave F ce a f t ron e? c a f ck a b r o

4 Transformations Matrices represent transformations: Linear Affine Projection?????

5 Transformations Matrices represent transformations: Linear Affine Projection Linear transformation Translation column Affine transformation Used for perspective projection Point

6 Transformations Matrices represent transformations: Linear Affine Projection Linear transformation? Translation column? Affine transformation? Used for perspective projection Point

7 Transformations Shift, move, add to coordinates Linear transformation Translation column Rotation x, y, z by fixed angle Shear x, y, z by fixed angle Scaling Affine transformation Preserves straight lines. Parallel lines stay parallel. Used for perspective projection Point

8 Shading What shading models are used here? Hint: Per-???

9 Lighting Basic lighting model consists of: Ambient Diffuse (Lambertian) Specular (Phong, Blinn-Phong) Where are they here? c I =max (0, n l ) 0.4+ max (0,(r v)) What are n, l, r, v and c?

10 Lighting Very important control question! Given diffuse reflection, which surface is more brighter? a) b)

11 Field Trip 3D Scanning Constructed model in Blender Pointcloud in MeshLab

12 Physics Simulation Rigid body What is it? Rigid body transformations Name them? Real-time rigid body collision algorithm: Approximate the object with a set of particles Detect the collisions between the particles Real-Time Rigid Body Simulation on GPUs:

13 Physics Simulation Soft body What is it? Simulation algorithms: Spring-mass models Finite element method... Collisions Discrete a posteriori, detected after collisions Continuous a priory, detected before collisions

14 Physics Simulation Physics Engines PhysX by Nvidia Havok by Intel Windows (free) Consoles Bullet library Blender LightWave 3D

15 Artists vs Programmers Art asset pipeline: Start with high-poly model? retopo? Use in a game? What model is used here? How? System Shock 2, Enhanced Dark Engine, poly w o ith l w t r sta -poly y l l a gh on Opti ake it hi and m here? g n i s s i m s i What

16 Blending When multiplying with the projection matrix, we try to also preserve the depth information. Z-buffer is used to draw objects in the correct order. Unfortunately, with a perspective projection, the resulting depth information is not linear (projection is not a linear transformation). This causes...?

17 Blending Depth information can be used for: Fog Depth of field Screen space ambient occlusion (SSAO) Shadows Soft particles Particle Chopper task, CGLearn Shadow mapping, CGLearn

18 Blending Objects can be semi-transparent and blended Conventional alpha blending Premultiplied alpha blending Which is which? blend (src, dest)=(src 1)+(dest (1 src alpha )) blend (src, dest)=( src src alpha )+(dest (1 src alpha )) New value to blend Value already in the buffer src source dest destination

19 Blending Different other combinations for the blending equation: Multiplicative blending Additive blending... General blending equation: World Remade by Jaanus Jaggo ex.php?topic= blend (src, dest)=( src src factor )func(dest dest factor ) Configurable parameters Try it yourself:

20 Shadows Shadow has 3 parts: Umbra Penumbra Antumbra What is the difference between a hard shadow and a soft shadow?

21 Shadows Static shadows objects that cast shadows do not move. Dynamic shadows objects that cast shadows do move. Lightmap static shadows and lights also do not move, this means that we can...?

22 Shadows Projected shadows shadows are just semi- transparent objects projected under other objects. Projection shadows project everything in the scene onto a plane (squash them). Shadow mapping use the depth information from a light source to determine if in the shadow. Shadow volume create separate shadow volume meshes by: Finding the silhouette of an object Projecting that from the light to infinity Count the number of times we pass the volumes

23 Shadow Mapping

24 Shadow Volume

25 Distance Fields 3D texture around the object that specifies, how far you are from the borders of that object.

26 Distance Fields Useful for font rendering, decals (logos) etc. Enlarging the distance field keeps the border in place. If this is the alpha, then we get a blurred edge If this is a distance field, then the borders stay the same

27 Distance Fields Unreal Engine 4.3 uses them for distance field ambient occlusions (DFAO).

28 Distance Fields Unreal Engine 4.5 uses them for soft shadows. Ray traced distance field soft shadows (RTDFSS) Shoot a ray from the fragment to a light source. March with the smallest distance in all the distance fields at the current step. If we hit an object instead, we are in full shadow. If we are close to some surface, approximate a cone trace to see, how much in the penumbra we are. Pick some n points along the ray to approximate. Details from the year Quote: It will very soon be realtime.

29 3D Fractal Generated Worlds with Cellular Automata Mathematical patterns are everywhere. 1, 1, 2, 3, 5, 8, 13, 21, 34, 55,...

30 3D Fractal Generated Worlds with Cellular Automata Fractal mathematical set that exhibits a pattern at every scale. The pattern can be self-similar The Mandelbrot set

31 3D Fractal Generated Worlds with Cellular Automata Cellular automation discrete mathematical model. Consists of cells, each of which has a state. States can change in time following some rules. Example: Convay's Game of Life Alive & <2 neighbours alive dead Alive & 2 or 3 neighb. alive alive Alive & >3 neighbours alive dead Dead & 3 alive neighbours alive

32 3D Fractal Generated Worlds with Cellular Automata Different rules? Different visualization? 1D Cellular Automata Pattern Generator (v 1.0) By John Henry Avila Perez

33 3D Fractal Generated Worlds with Cellular Automata 2D Cellular Automata Pattern Generator By John Henry Avila Perez

34 3D Fractal Generated Worlds with Cellular Automata 3D Cellular Automata Pattern Generator John Henry Avila Perez,

35 Natural Simulation with JavaScript using Processing.js Simulation imitation of the operation of a realworld process over time. Processing.js JavaScript port of Processing language. Used for: 2D and 3D visualizations Interactive applications (eg games) Animations...

36 Natural Simulation with JavaScript using Processing.js Randomness lack of predictability or pattern random(high), random(low, high) Noise can be used for natural looking textures Eg Perlin noise noise(x), noise(x, y), noise(x, y, z)

37 Natural Simulation with JavaScript using Processing.js Vector object with magnitude and direction PVector class (has methods for operations) Object preserves its speed and direction, unless acted upon by an unbalanced force. Force=mass acceleration Angular movement Oscillation...

38 Natural Simulation with JavaScript using Processing.js Moshpit Simulation Seems to use JS context drawing only

39 Natural Simulation with JavaScript using Processing.js My Life Aquatic, BitTorrent visualization, Delaunay Triangulation:

40 Animation Key principles: Squash and stretch Anticipation Staging Straight ahead & pose to pose Follow through & overlapping Slow in and slow out Arcs Secondary action Timing Exaggeration Solid drawing Appeal

41 Animation Interpolation of vertex groups between stances Linear Using curves why? Types of animation: Morph target Skeletal meshes Kinematics Key frame animation Motion capture

42 Game Development in JavaScript Game cycles Which is better? Why?

43 Game Development in JavaScript JavaScript n-body benchmark Faster than: Lua Python PHP Slower than: C++ C# Fortran Haskell Clojure Go php?test=nbody

44 Game Development in JavaScript Sometimes a bit weird behaviour RequireJS + OOP Three.js graphics library Some physics libraries (with bad doc) Cannon Ammo Box2D PhysiJS

45 Game Development in JavaScript Back to collision detection: Broad phase find candidates for testing Need to partition the space to avoid O (n 2 ) Narrow phase test the candidates Bounding objects Test path intersection

46 Game Development in JavaScript GTA 2 remake in JS by Erich Jagomägis

47 CGLearn Computer graphics learning environment Has interactive examples in JavaScript

48 Feedback How did you like the seminar organization? Did you found our activities interesting / useful? Which ones especially? What would you change?

49 Thanks for listening!