Computer Graphics Seminar MTAT.03.296 Spring 2014 Raimond Tunnel - - PowerPoint PPT Presentation

Computer Graphics Seminar

MTAT.03.296 Spring 2014

Raimond Tunnel

Conclusion!

Geometry & Algebra

(

cos(0.6) −sin(0.6) 1 sin(0.6) cos(0.6))

= ?

Geometry & Algebra

(

cos(0.6) −sin(0.6) 1 sin(0.6) cos(0.6))

= =

Geometry & Trigonometry

Geometry & Trigonometry

Lighting Models

(r

T⋅v) c⋅LSpecular⋅M Specular

(n

T⋅ v+r

∣v+r∣)

c

⋅LSpecular⋅M Specular

? ? ?

Lighting Models

(r

T⋅v) c⋅LSpecular⋅M Specular

(n

T⋅h) c⋅LSpecular⋅M Specular

Phong Blinn

h= v+r ∣v+r∣

Lighting Models

c=0 c=30 c=300

No specular, Only diffuse Soft and wide specular Sharp and narrow specular

Phong's model I=L A⋅M A+ 1 d light

2 ⋅(n T⋅l⋅L D⋅M D+(r T⋅v) c⋅LS⋅M S)

Physically Based Shading

f microfacet(l ,v)= F (l ,h)⋅ G(l ,v ,h)⋅D(h) 4⋅ (n⋅l)⋅ (n⋅v)

Returns how much light reflects Geometry function Distribution function Fresnel effect

Physically Based Shading

G(l ,v ,h ,n)

• How much light is

not blocked?

• How much surface

is not blocked from a viewer?

• How much points

are visible from both a viewer and a light source?

Shadowing Masking

Physically Based Shading

• How much microsurface normals point

towards the macrosurface normal?

D(h)

Particle Systems

Particle Systems

Particle Systems

http://chrisp.gr/projects/boids/

• Particles can have more

interesting logic (e.g. the Boids algorithm)

• Many particles may

cause performance issues.

Unreal Engine 4

Procedural Generation

• Let the computer generate our content via procedures

(methods, functions, rulesets etc).

• Particles are also procedurally generated.
• Other things can be generated, like worlds, houses,

weapons, NPCs, trees.

Procedurally generated Terraria map

Procedural Generation

Terraria

Procedural Generation

• Lindenmayer systems (1968).
• The Algorithmic Beauty of Plants (1990)

http://algorithmicbotany.org/papers/abop/abop.pdf

• Aristid Lindenmayer (1925 – 1989)
• L-system – Parallel rewriting system, formal grammar
• Deterministic 0-context L-systems
• Stochastic L-systems
• Context sensitive L-systems

Procedural Generation

F → FG G →GF F F FG FGGF FGGFGFFG

Iteration 1 Iteration 1 Iteration 1 Iteration 2 Iteration 3 Ruleset Starting axiom Procedure

• Parallel rewriting

system

• Formal grammar

Procedural Generation

Symbol Interpretation F Draw a segment [ Push current state into stack ] Pop state from stack + Turn 30 degrees left around z-axis

• Turn 30 degrees right

around z-axis

Turtle graphics http://en.wikipedia.org/wiki/Turtle_graphics

Procedural Generation

F

0.5

→ F [^ F [+F ][−F ]] F

0.5

→ F [& F [+F ][−F ]]

Ruleset

F

Starting axiom Iterations: 3 S t

• c

h a s t i c s y s t e m

3D Scan Data

• Large amount of points
• Model filled with holes and noise

3D Scan Data

• Remove outliers
• Surface

Reconstruction (e.g. Poisson)

• Reconstruct parts
• f the surface

individually with different parameters

3D Scan Data

• Lower the vertex count (decimation).

3D Scan Data

• Export from Geomagic Studio, MeshLab, ...
• Import into Blender

Realtime Realistic Rendering

Motion Blur Depth of Field R e f l e c t i

• n

s P h y s i c s OctaneRender 2.0

Realtime Realistic Rendering

• Voxel Octree Cone Tracing
• NVIDIA, 2011

https://research.nvidia.com/sites/default/files/publications/GIVoxels-pg2011-authors.pdf

• Algorithm for indirect illumination

Glossy reflections, color bleeding Indirect diffuse lighting

Realtime Realistic Rendering

• Voxel Octree Cone Tracing
• Distribute radiance from light sources
• Distribute radiance inside octree
• For a viewed point, cone-trace indirect illumination

Images taken from the article... Maybe??

Non-(photo)realistic Rendering

• Cel-shading / toon shading

Non-(photo)realistic Rendering

• Cel-shading / toon shading
• Quantize the colors, illumination, pixel values
• Black border

float binCount = 6.0; frag_color.x = floor(frag_color.x * binCount) / binCount; frag_color.y = floor(frag_color.y * binCount) / binCount; frag_color.z = floor(frag_color.z * binCount) / binCount; gl_FragColor = frag_color;

F r a g m e n t s h a d e r ( + 4 l i n e s

• f

c

• d

e )

Non-(photo)realistic Rendering

• Black border
• Any edge detection algorithm on the depth texture

and on the normal texture

Quantized render Depth texture (z-buffer) Normal vector texture Detected edges Result with black border

Non-(photo)realistic Rendering

• Black border
• Any edge detection algorithm...

– Sobel (first order derivative) – Laplacian (second order derivative)

√

1 (1+x

10)

Butterworth

( f ∗g)[ x , y]=∑

i=−d d

∑

j=−d d

f (x+i , y+ j) ⋅g (x+i , y+ j)

Convolution of an image with a kernel (d x d) 1 1 1 1

• 8

1 1 1 1 1 1

• 4

1 1

• 1

1

• 2

2

• 1

1

• 1
• 2
• 1

1 2 1 Laplacian kernels Use only one Sobel kernels for x and y Use both and sum absolute values from results

Non-(photo)realistic Rendering

• Jot, FreeStyle, ...

Computing on the GPU

http://www.mathworks.se/company/newsletters/articles/gpu-programming-in-matlab.html

Computing on the GPU

• Use frame-buffer object (FBO) and do dummy rendering
• OpenCL
• CUDA (for NVIDIA cards)

Platform Device 1 Device 2 CPU GPU Data: [0.0, 1.0, 2.0, 3.0, ...] Data: [0.0, 1.0, 4.0, 9.0, ...]

Computing on the GPU

Other activities

• Martti Savolainen

(3D Technologies)

• Fille Mazendacus

(Tartu Art School)

• 3D scanning

(Institute of Technology)

The End

The End

• How was the seminar?
• Did it correspond to your expectations?
• What should we do differently?
• Was there anything you would have like to have done

that we didn't have time for?

• Are you joining us again next semester?