graphics graphics lab @ korea university cgvr.korea.ac.kr 1 chapter 6 special effects 강 신 진강...

Graphics

cgvr.korea.ac.kr 1 Graphics Lab @ Korea University

Chapter 6 Special Effects

강 신 진

2002.04.242002.04.24

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2 Graphics Lab @ Korea University

What?

What is Special Effects? Relative term in computer graphics New way of performing old algorithms

온라인 게임 - 뮤

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Index

Image-Based Rendering Lens Flare and Bloom Billboarding Full-Screen Billboarding Particle System Fixed-View Effects

Motion Blur Depth of Field Reflections

Planar Reflections Glossy Effects Reflections from Curved Reflectors

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Polygon-Based Rendering Use polygon to portray image Can represent the object in any view

Image-Based Rendering Use images to portray image Can gain speed advantage

Image-Based Rendering

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Image-Based Rendering - Sprite

What is Sprite? An Image that moves around on the screen Simplest image-base rendering primitive

Implementation An image texture on a polygon with the use of alpha

channel

+ =

배경화면 스프라이트 결과화면

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Example

Matrox Graphics Power of 3D Demo

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Example


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Image-Based Rendering – QuickTime VR

QuickTime VR Use a 360` panoramic image surrounds the viewer

as a cylindrical image Optimized for cylindrical environment mapping

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Image-Based Rendering

Limitation When to Warp and When to Regenerate?

Microsoft Chicken Crossing

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Index




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Lens Flare and Bloom

Sample

nVIDIA Effect Browser

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Lens Flare Phenomenon caused by the lens of the eye or

camera when directed at bright light Consist of Halo and Ciliary Corona

Bloom Phenomenon caused by scattering in the lens and

other part of the eye Halo

Ciliary Corona

Bloom

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Sample

nVIDIA Effect Browser

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Billboarding

Billboarding Orienting the polygon based on the view direction

Billboard The polygon which is oriented

Direct3D Billboarding Tree

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Billboarding – Screen-Aligned

Screen-Aligned Billboarding Billboard face the screen Billboard normal is negation of the view direction Rotate n to align with –Vdir, the rotate u’ to align with

Vup

u’

Vup

Vdir

n

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World-Aligned Billboarding Billboard face the screen but aligns with the world’s

up-vector Wup

Billboarding – World-Aligned

dirup VWr rVt dirup

tup

Wup

Vdir

rn

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Axial-Aligned Billboarding Billboard rotate around fixed world-space axis and

align with viewer as possible within range

Billboarding – Axial-Aligned

updir WVs sWt updir

tdir

WupVdir

s

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Full-Screen Billboarding

Full-Screen Billboarding A Screen-align billboard that covers the entire view Can change the look of an environment

id Software Quake III

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Index




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Particle Systems

Particle System A set of separate small objects that are set into

motion using some algorithm Creating, moving, changing, and deleting particles

nVIDIA Particle Demo

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Fixed-View Effects

Fixed-View The view is fixed to one location and orientation Using depth information from a real scene to be seen

more realistic Static image can be made to look more realistic

3D 수족관 화면 보호기

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Index




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Motion Blur

Blurring Can add the feeling of motion Average a series of images using accumulation

buffer

Motion Blur created by accumulation buffer

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Index




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Depth of Field

Depth of Field Objects which is out of focus are blurry

nVIDIA Depth of Field

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Index




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Reflections

Reflection and Shadows Generated by lighting equation Can increase realism Used by viewer as a cues to determine spatial

relationships between objects

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Reflections

Reflector and Reflected Geometry Reflector: a reflecting surface Reflected Geometry: Geometry reflected in the

reflector

Ray Tracing Solution in which the reflection ray is emitted from a

reflector and recursively traced Computationally intensive for real-time system Need real-time solution

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Reflections – Planar Reflections

Planar Reflection Reflection off a flat surface - Mirror reflection Execute more rapidly than general reflection Follows the law of reflection

Can be Implemented by Copy & Transforming

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Reflection Matrix F = R (n, (0,1,0))T(-p) M = F-1 S(1,-1,1) F

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Reflectivity factor Applied by changing transparency

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Stencil Buffer Support selective Planar Reflections

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Problem Area Culling

Turn off face culling or front face culling

Clipping Clipping Plane

Another Technique Reflection image can be treated as a texture

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Glossy Effects

Glossy Effects Object face to black as the distance from the reflector

increase Distance calculation is needed

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Reflections from Curved Reflector

Traditional Solution Ray-Tracing Not good for real-time system

Selective Trace Ray Trace rays only from the reflector’s vertices into

environment Significantly reduce computation time but still suffer

from Gouraud-Shading artifacts

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Question





graphics graphics lab @ korea university cgvr.korea.ac.kr 1 chapter 6 special effects 강 신 진강...

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