Graphics Graphics Korea University cgvr.korea.ac.kr 1 Chapter 6 Special Effects 강 신 진강 신 진

CGVR Graphics Korea University cgvr.korea.ac.kr 2 What? What is Special Effects? Relative term in computer graphics New way of performing old algorithms 온라인 게임 - 뮤

CGVR Graphics Korea University cgvr.korea.ac.kr 3 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

CGVR Graphics Korea University cgvr.korea.ac.kr 4 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

CGVR Graphics Korea University cgvr.korea.ac.kr 5 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 스프라이트결과화면

CGVR Graphics Korea University cgvr.korea.ac.kr 6 Image-Based Rendering - Sprite Example Matrox Graphics Power of 3D Demo

CGVR Graphics Korea University cgvr.korea.ac.kr 7 Image-Based Rendering - Sprite Example Matrox Graphics Power of 3D Demo

CGVR Graphics Korea University cgvr.korea.ac.kr 8 Image-Based Rendering – QuickTime VR QuickTime VR Use a 360` panoramic image surrounds the viewer as a cylindrical image Optimized for cylindrical environment mapping

CGVR Graphics Korea University cgvr.korea.ac.kr 9 Image-Based Rendering Limitation When to Warp and When to Regenerate? Microsoft Chicken Crossing

CGVR Graphics Korea University cgvr.korea.ac.kr 10 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

CGVR Graphics Korea University cgvr.korea.ac.kr 11 Lens Flare and Bloom Sample nVIDIA Effect Browser

CGVR Graphics Korea University cgvr.korea.ac.kr 12 Lens Flare and Bloom 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

CGVR Graphics Korea University cgvr.korea.ac.kr 13 Lens Flare and Bloom Sample nVIDIA Effect Browser

CGVR Graphics Korea University cgvr.korea.ac.kr 14 Billboarding Orienting the polygon based on the view direction Billboard The polygon which is oriented Direct3D Billboarding Tree

CGVR Graphics Korea University cgvr.korea.ac.kr 15 Billboarding – Screen-Aligned Screen-Aligned Billboarding Billboard face the screen Billboard normal is negation of the view direction Rotate n to align with –V dir, the rotate u’ to align with V up u’ V up V dir n

CGVR Graphics Korea University cgvr.korea.ac.kr 16 World-Aligned Billboarding Billboard face the screen but aligns with the world’s up-vector W up Billboarding – World-Aligned t up W up V dir r n

CGVR Graphics Korea University cgvr.korea.ac.kr 17 Axial-Aligned Billboarding Billboard rotate around fixed world-space axis and align with viewer as possible within range Billboarding – Axial-Aligned t dir W up V dir s

CGVR Graphics Korea University cgvr.korea.ac.kr 18 Full-Screen Billboarding A Screen-align billboard that covers the entire view Can change the look of an environment id Software Quake III

CGVR Graphics Korea University cgvr.korea.ac.kr 19 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

CGVR Graphics Korea University cgvr.korea.ac.kr 20 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

CGVR Graphics Korea University cgvr.korea.ac.kr 21 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

CGVR Graphics Korea University cgvr.korea.ac.kr 22 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

CGVR Graphics Korea University cgvr.korea.ac.kr 23 Motion Blur Blurring Can add the feeling of motion Average a series of images using accumulation buffer Motion Blur created by accumulation buffer

CGVR Graphics Korea University cgvr.korea.ac.kr 24 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

CGVR Graphics Korea University cgvr.korea.ac.kr 25 Depth of Field Objects which is out of focus are blurry nVIDIA Depth of Field

CGVR Graphics Korea University cgvr.korea.ac.kr 26 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

CGVR Graphics Korea University cgvr.korea.ac.kr 27 Reflections Reflection and Shadows Generated by lighting equation Can increase realism Used by viewer as a cues to determine spatial relationships between objects

CGVR Graphics Korea University cgvr.korea.ac.kr 28 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

CGVR Graphics Korea University cgvr.korea.ac.kr 29 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

CGVR Graphics Korea University cgvr.korea.ac.kr 30 Reflections – Planar Reflections Reflection Matrix F = R (n, (0,1,0))T(-p) M = F -1 S(1,-1,1) F

CGVR Graphics Korea University cgvr.korea.ac.kr 31 Reflections – Planar Reflections Reflectivity factor Applied by changing transparency

CGVR Graphics Korea University cgvr.korea.ac.kr 32 Reflections – Planar Reflections Stencil Buffer Support selective Planar Reflections

CGVR Graphics Korea University cgvr.korea.ac.kr 33 Reflections – Planar Reflections Problem Area Culling  Turn off face culling or front face culling Clipping  Clipping Plane Another Technique Reflection image can be treated as a texture

CGVR Graphics Korea University cgvr.korea.ac.kr 34 Glossy Effects Object face to black as the distance from the reflector increase Distance calculation is needed

CGVR Graphics Korea University cgvr.korea.ac.kr 35 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

CGVR Graphics Korea University cgvr.korea.ac.kr 36 Question 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 Matrox Graphics Power of 3D Demo