Architectural Walkthroughs

CG Lab

박사 3 차류승택

발표 내용

가상공간에서의 실시간 렌더링 관련 논문 (UNC)

“Architectural Walkthroughs Using Portal Textures”, 1997 년 (IEEE Visualization 97)

“3D Image Warping in Architectural Walkthroughs”, 1998. 3 (VRAIS ‘98)

“Efficient Warping for Architectural Walkthroughs using LDIs”, 1998. 10 (IEEE Visualization 98)

“Image for Accelerating Architectural Walkthroughs”, 1998. 12 (CG&A)

기본 개념

High quality architectural walkthroughs require large and complex models reducing rendering time

• Subdividing it into cells and portals– Using Portal Culling– do not reduce the amount enough

• Portal Texture– the use of images at portals as replacements for the geometry

seen through the portal

Portal Culling vs Portal Texture

<Portal Culling> <Portal Texture>

Portal Texture: Image

Portal Texture

Portal Texture 의 표현 using conventional texture using image based rendering

• using image warping

• using Layered Depth Image

Conventional texture: Texture selection

Conventional texture: Constrained Model

Define values Viewing Height Sampling Distance Transition Distance Viewing Angles

Conventional texture: Morphing

Conventional texture: visibility-determination algo.Visibility(cell, frustum) {

Mark cell visibleCull cell to frustumForeach portal {

Cull portal to frustumif (portal is visible) {

if (portal in transition)Initialize transition

else if (portal is texture)Choose best texture sample

else if (portal is geometry)Visibility(portal’s adjacent cell, culled frustum)

}if (portal in transition) {

Next transition stepif (portal->texture finished)

Choose best texture sampleif (texture->portal finished)

Visibility(portal’s adjacent cell, culled frustum)}

}}

Conventional Texture : Problem

Texture single texture

• 커다란 그림이 벽에 걸려 있는 듯한 느낌 Multiple textures

• switch between them as we move

• disadv: – popping effect, motion parallax

• solution

– image warping

Portal Warping: Image Warping

Image Warping

Portal Warping: Exposure

Solution increase the number

of reference image per portal warp multiple reference images

• three visibility cases – both reference image contains information about the same

geometry– one image contains information absent from the other image

» resolve visibility----> use z-buffering– information about some geometry is missing from both images

Portal Warping: Problem

Problem Incorrect visibility

• Do not guarantee correct visibility when multiple images are warped to the desired view

• using expensive z-buffering

redundant works• warping two images incurs redundant work since many of the

samples are identical.

Layered Depth Images

Construction LDIs• central image is stored in the LDI

• remaining images are warped to the plane of the central image

– sample lands at an empty location» Store

– sample lands at an occupied location

» store only if it represents a different surface

» Threshold or Color

Warping LDIs• it behaves like like a single image

when warped

Images:Single reference vs Two references

Images:LDI vs Geometry

Images:Layers of a LDIs