View-Dependent RefinementView-Dependent Refinementof Progressive Meshesof Progressive Meshes

Hugues HoppeHugues HoppeMicrosoft ResearchMicrosoft Research

SIGGRAPHSIGGRAPH 97 97

Rendering complex meshesRendering complex meshes

860,000 faces!860,000 faces!860,000 faces!860,000 faces! VV FF

Traditional level-of-detailTraditional level-of-detail

50,000 faces50,000 faces

progressive meshprogressive mesh representation representation [SIGGRAPH96][SIGGRAPH96]

10,000 faces10,000 faces2,000 faces2,000 faces

view-independent LODview-independent LODlinear sequencelinear sequence

poppop poppop

View-Independent LOD: DifficultiesView-Independent LOD: Difficulties

100,000 faces100,000 facesoutsideoutside

view frustumview frustum

distantdistant

backfacingbackfacing

SS

View-dependent LODView-dependent LOD

29,400 faces29,400 faces different LOD’s coexistdifferent LOD’s coexistover surfaceover surface

Applications & Related workApplications & Related work

heightfields

parametricsurfaces

arbitrarymeshes

[Cignoni etal 95][De Floriani etal 96][Lindstrom etal 96]

…

[Rockwood etal 89][Abi Ezzi etal 93][Kumar etal 95]

…

[Xia-Varshney 96]

SS

ContributionsContributions

Progressive meshProgressive mesh vertex hierarchy vertex hierarchy selective refinement selective refinement

Dependencies Dependencies consistent framework consistent framework

View-dependent refinement criteriaView-dependent refinement criteria

base meshbase mesh original meshoriginal mesh

150150

MM00 MM11

152152

Review of Review of progressive meshesprogressive meshes

… … MM175 175 ……

500500 13,54613,546

MMnn

vvll vvrr

vvuu

vvtt

vvssvvll vvrr

edge collapseedge collapse

vertex splitvertex split

150150

MM00 MM11

vsplvspl00

152152

The PM representationThe PM representation

MM175175

500500

… … vsplvsplii … …

13,54613,546

vsplvspln-1n-1

MMnn

progressive mesh (PM)progressive mesh (PM) representation representation

vsplvspl00 … … vsplvsplii … … vsplvspln-1n-1

MM00

MM00 MMnnMMii

MMnn

Idea: Selective refinementIdea: Selective refinement

MM00 vsplvspl00 vsplvspl11 vsplvspli-1i-1 vsplvspln-1n-1

[SIGGRAPH 96]: incremental update not possible[SIGGRAPH 96]: incremental update not possible

Parent-child vertex relationsParent-child vertex relations

vvss

vvttvvuu

vsplitvsplit

vv22

Vertex hierarchyVertex hierarchy

vsplvspl00MM00 vsplvspl11 vsplvspl22 vsplvspl33 vsplvspl44 vsplvspl55

vv11 vv33MM00

vv1010 vv1111

vsplvspl33

vv11 vv22

vv44 vv55

vsplvspl00

vv88 vv99

vsplvspl22

vv33

vv66 vv77

vsplvspl11

vv55

vv1212 vv1313

vsplvspl44

vv1010

vsplvspl55

vv1414 vv1515

vv66

PM:PM:

MMnn

[Xia & Varshney 96]

MM00

vsplvspl22

vv1111

vv11 vv22

vv44 vv88 vv99

vv33

vv77

vv55

vv1212 vv1313

vv1010

vv1414 vv1515

vv66

vv22

Selective refinementSelective refinement

vsplvspl00MM00 vsplvspl11 vsplvspl33 vsplvspl44 vsplvspl55

vv11 vv33MM00

vv1010 vv1111

vsplvspl33

vv11 vv22

vv44 vv55

vsplvspl00

vv66 vv77

vsplvspl11

vv55

vv1212 vv1313

vsplvspl44

vv1010

selectively refined meshselectively refined mesh

vv88 vv99

vsplvspl22

vv33

vv88 vv99

vsplvspl22

vv33

Restrictions?Restrictions?

Legality conditions?Legality conditions?

vvll vvrr

vvuu

vvtt

vvssvvll vvrr

vsplitvsplit

ecolecol vsplitvsplit legal if: legal if:

– vvss is active is active– vvll and and vvrr are active are active

ecolecol legal if: legal if:– ? problem: consistent?? problem: consistent?

[SIGGRAPH96][SIGGRAPH96]

[Xia&Varshney96]: legal if identical neighborhood

New vspl/ecol parametrizationsNew vspl/ecol parametrizations

vsplitvsplit

ecolecol

ffn1n1

ffn0n0

vvss

ffn3n3

ffn2n2

ffn1n1

ffn0n0

vvuu

vvtt

ffn3n3

ffn2n2

vsplitvsplit legal if: legal if:– vvss is active is active– ffn0n0,f,fn1n1,f,fn2n2,f,fn3n3 are active are active

ecolecol legal if: legal if:– vvtt,v,vuu are active are active– ffn0n0,f,fn1n1,f,fn2n2,f,fn3n3 are adjacent are adjacent

previous meshprevious mesh

vv55vv1010 vv1111 vv44 vv88 vv99

vv77vv1212 vv1313

vv11 vv22 vv33

Runtime algorithmRuntime algorithm

MM00

vv66

vv1414 vv1515

vv1212 vv1313vv1212

vv1010 vv1111vv1010 vv1111 vv44vv44

vv66

vv1414 vv1515

vv66

vv1414 vv1515

vv88 vv99

vv33

vv1515

vv77vv77

vv88vv88 vv99vv99

new meshnew mesh

dependencydependency

Algorithm:Algorithm: incremental (frame coherence)incremental (frame coherence) efficient (~15% of frame time)efficient (~15% of frame time) amortizableamortizable

vv1111vv1010 vv44

vv1414 vv1515

vv77

vv88 vv99

View-dependent refinement criteriaView-dependent refinement criteria

3 criteria:3 criteria:

view frustumview frustum

surface orientationsurface orientation

screen-space geometric errorscreen-space geometric error

See paper for details.See paper for details.

SS

(1) View frustum(1) View frustum

too hightoo high too far righttoo far rightview is unchangedview is unchanged

(2) Surface orientation(2) Surface orientation

view is unchangedview is unchanged oriented awayoriented away

(3) Screen-space geometric error(3) Screen-space geometric error

refinement near refinement near silhouettesilhouette

coarser in coarser in distancedistance

tolerance=0.5 pixelstolerance=0.5 pixels

All three criteria togetherAll three criteria together

69,473 faces 69,473 faces 10,528 faces 10,528 faces1.9 frame/sec 1.9 frame/sec 6.7 frame/sec 6.7 frame/sec

SS

Fast rendering: triangle stripsFast rendering: triangle strips

Greedy algorithm:Greedy algorithm: IRIS GL:IRIS GL:

avg. 10-15 faces/stripavg. 10-15 faces/strip

OpenGL:OpenGL:avg. 4.2 faces/stripavg. 4.2 faces/strip

32 Bezier patches32 Bezier patches

Application: Parametric surfacesApplication: Parametric surfaces

PMPM

MM00

pre-pre-processprocess

vsplvspl

25,44025,440

VV FF

MM vv11MM00 vv22

vv33 vv44 vv55 vv66

vv77 vv88

MMnnloadload

10,00010,0001,8001,800

GeomorphsGeomorphs

M A

v8 v9v4 v5

v6 v7

v12 v13

v1 v2 v3

v10 v11

v14 v15

M B

M G

smooth visual transitionssmooth visual transitions

VIDEOVIDEO

view frustum (2-window terrain)view frustum (2-window terrain)screen-space error (2-window terrain)screen-space error (2-window terrain)

silhouette refinement (sphere)silhouette refinement (sphere)all 3 criteria including orientation (teapot)all 3 criteria including orientation (teapot)

arbitrary mesh (gameguy)arbitrary mesh (gameguy)geomorphgeomorph

flythrough of gcanyonflythrough of gcanyon

SummarySummary

Selective refinement frameworkSelective refinement framework

View-dependent refinement criteriaView-dependent refinement criteria

Real-time algorithm (fast, amortizable)Real-time algorithm (fast, amortizable)

Arbitrary progressive meshesArbitrary progressive meshes

geometrically optimized refinement! geometrically optimized refinement!

Future workFuture work

Memory management for large modelsMemory management for large models

Runtime generation of geomorphsRuntime generation of geomorphs

Refinement criteria for surface shadingRefinement criteria for surface shading

Animated modelsAnimated models