pop: a hybrid point and polygon rendering system for large … · 2015. 11. 25. · may 17, 2001...

May 17, 2001

POP: A Hybrid Point and Polygon Rendering System for Large Data

Baoquan ChenMinh X. Nguyen

Computer Science & Engineering DepartmentUniversity of Minnesota at Twin Cities

http://www.cs.umn.edu/~baoquan

This work is to appear in IEEE Visualization 2001

2Baoquan Chen 2001 4 millions samples

3Baoquan Chen 200114 millions samples

4Baoquan Chen 2001

Volumetric DataVolumetric Data

MRICTPETUltrasonography

Confocal Microscopy

Micro-Tomography

Simulated DatasetsVoxelized

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Mixing of Polygons and Volumes

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Surface model Novel view

Key view

Texture mapping

Image-based Rendering

Filling holes(ray casting)

7Baoquan Chen 2001

Architecture Design

UnifiedPipeline

Texture

Me

mo

ry

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3D Volume Rotation

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x

y

z

a y

b z

x beam shear:

x = x + a y + b z

Rotation by 4 2D Beam Shears

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Rotation by 4 2D Beam Shears

original

1. y beam shear 2. z beam shear

3. x beam shear 4. y beam shear

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x

y

z

a y

b y

y slice shear:

x = x + a yz = z + b y

Rotation by 4 2D Slice Shears

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Rotation by 4 2D Slice Shears

1. y slice shear 2. z slice shear

3. x slice shear 4. y slice shear

original

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x

y

z

b y

g z

a y x-beam y-slice shear:

Rotation by 3 2D Beam-Slice Shears

x = x + a y + g z z = z + b y

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Rotation by 3 2D Beam-Slice Shears

3. y beam shear2. x beam y slice shear

1. y beam x slice shear

original

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x

y

z

y-slice

z-slice

x-beamR = Sx Sz

3D 3D

Rotation by 2 3D Beam Shears

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Rotation by 2 3D Beam Shears

original gazebo after interpolation

first 3D integer shear second 3D integer shear

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POP System

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Goals

•Maintain interactive frame rate for large models (108 – 109 samples) on commodity graphics hardware

+

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Previous Systems (I)

•Level of detail representation and control [Funkhouser 93] [Duchaineau 97] [Hoppe 96, Hoppe 97][Xia 97] ……

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Previous Systems (II)• Visibility Culling

[Greene & Kass 93][Zhang et al. 97] ……

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Previous Systems (III)•Point representation and rendering

Levoy & Whitted 1985Shade, et al. 1998 (LDI)Grossman & Dally 1998Rusinkiewicz & Levoy 2000 (Qsplat)Pfister, et al. 2000 (Surfel)……

Wand, et al. 2001Zwicker, et al. 2001Pauly & Gross 2001

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Qsplat (I)

•Place a sphere at each node, large enough to touch neighbor spheres

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Qsplat (II)

•Build-up a bounding sphere hierarchy to facilitate efficient rendering

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Surfel• A given mesh is sampled on multiresolution

rectilinear grids.• Points on the same level have the same size.

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Problems (I)

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Problems (II)

Polygon Point

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PointsPolygons

Polygons vs. Points

Good for large, flat orsubtly curved regions

Good for models withdetail everywhere

Incremental rasterization Independent rasterization

LOD data structuresmore complex (expensive)

LOD data structures straightforward

Backward processing Forward processing

Connectivity ensuresinterpolation

No connectivitythus, holes/splats

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POP system

PreprocessingView Information

Rendering Engine

Screen Image

MeshPreprocessed

Data

• Preprocessing: Build-up data hierarchy

• Rendering: traverse tree and render points or polygons

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Hierarchical structure of POP

V 0V 2V 1 V 0V 4V 1 V 0V 3V 2V 0V 4V 3

V 2

V 1

V 3

V 4

V 0

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QSplatPOP

POP vs. Qsplat

Works best when the faces of models have uniform size

The topology of the mesh is discarded

The topology of the mesh is partially kept

Works for arbitrary models

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Node Structure

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V 0V 2V 1 V 0V 4V 1 V 0V 3V 2V 0V 4V 3

32Baoquan Chen 2001

Node Structure

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• Tight bounding sphere• Error can be accumulated• Compact representation

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Node Structure

• Number of children (0, 2, 3, or 4)• Rendering flags

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34Baoquan Chen 2001

Node Structure

• Average of children’s normals• Or, if leaf child, average of the normals

of the leaf triangle’s three vertices• Normal quantized to grid on faces of a

cube

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35Baoquan Chen 2001

Node Structure

• Each node contains bounding cone ofchildren’s normals

• Hierarchical backface culling [Kumar 96]

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CulledCulled Not CulledNot Culled

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36Baoquan Chen 2001

Node Structure

• The intermediate node color is the average of children nodes’ colors

• The leaf node color is the average of the whole triangle (pre-texture mapping)

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37Baoquan Chen 2001

Rendering Algorithm (I)

•T raverse hierarchy recursively

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38Baoquan Chen 2001

Rendering Algorithm (II)

• Utilize coherence

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Source image

Target image

High Quality Texture Mapping

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magnification

mixed

minification

mixed

Four-Region Subdivision

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Forward Footprint Projection (Splatting)

Source image Target image

Texture Mapping Methods (I)

ExpensiveExpensive(Ellipsoid evaluation)(Ellipsoid evaluation)

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Forward Point Projection

Source image Target image

Texture Mapping Methods (II)

•• Efficient (Circular filter)Efficient (Circular filter)•• Good forGood for minificationminification

regionregion

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Backward Footprint Projection (EWA)

Source image Target image

Texture Mapping Methods (III)

ExpensiveExpensive(Ellipsoid evaluation)(Ellipsoid evaluation)

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Backward Point Projection (BiLin or MIPMAP)

Source image Target image

Texture Mapping Methods (IV)

•• Efficient (Efficient (bibi-- or trior tri--linear interpolationlinear interpolation))

•• Good for magnification Good for magnification regionregion

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•• For For minificationminification region: forward point region: forward point projection (projection (splattingsplatting) )

•• For magnification region: backward For magnification region: backward point projectionpoint projection

Hybrid Order Rendering

Point renderingPoint rendering

Polygon renderingPolygon rendering

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Backward Bilinear Interpolation

AliasingAliasing

Good qualityGood quality

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Pure Point Rendering

Good qualityGood quality

Bad qualityBad quality

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Hybrid Polygon-Point Rendering

Good qualityGood quality

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Results

•Hardware: 800 MHZ Pentium III PC w/ 256 MB

•NVIDIA GeForce2 GTS

1,087,716 triangles654,666 triangles

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Results

51Baoquan Chen 2001QSplat POP

Results

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QSplat POP

Results

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Results

QSplatPOP

Thres = 1.0272,047 pts,255,708 tris,1.62fps

Thres = 1.0317,557 pts,

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Results

Thres = 2.0267,567 pts,48,143 tris,2.84 fps

Thres = 3.4147,263 pts,7,348 tris,5.43 fps

POPPOP QSplat

Thres = 1.0317,557 pts,