An Enhanced Splatting MethodAn Enhanced Splatting Method

Graphics and Visualization Group

Department of Computer Science

The University of Auckland

Peter Kulka & Richard Lobb

ACSC’99 - An enhanced splatting method - Peter Kulka & Richard Lobb

OverviewOverview

• Direct volume rendering

• High resolution splatting

• Results

• Conclusions and future work

ACSC’99 - An enhanced splatting method - Peter Kulka & Richard Lobb

Direct volume renderingDirect volume rendering

• Research area within visualization

• Rendering of 3D volume data sets– Volume reconstruction– Calculating an illumination model

• Two classes of algorithms:– Ray casting– Projection methods (splatting)

ACSC’99 - An enhanced splatting method - Peter Kulka & Richard Lobb

Volume reconstructionVolume reconstruction

• Problem:– Finding values between sample points

ACSC’99 - An enhanced splatting method - Peter Kulka & Richard Lobb

Illumination modelsIllumination models

• Assigning optical properties to the volume

• Emission-absorption model:– Volumes consist of light emitting particles– Particles also attenuate light from behind them

• Such a system can be described by:

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ACSC’99 - An enhanced splatting method - Peter Kulka & Richard Lobb

Ray castingRay casting

• Image order method

• Simulation of light flow along viewing rays

• Sharp images

ACSC’99 - An enhanced splatting method - Peter Kulka & Richard Lobb

SplattingSplatting

• Object order method

• Projection of each volume element onto the view plane

• Fast

ACSC’99 - An enhanced splatting method - Peter Kulka & Richard Lobb

MotivationMotivation

• Want:– Rendering speed of splatting– Image quality of ray casting

• Approach:– Correct errors in splatting

• Leads to three separate modifications

• Result: sharper images– We call this method high resolution splatting

ACSC’99 - An enhanced splatting method - Peter Kulka & Richard Lobb

Modifications to standard splattingModifications to standard splatting

• Reordering reconstruction and illumination calculations

• Correcting view angle distortions

ACSC’99 - An enhanced splatting method - Peter Kulka & Richard Lobb

Modifications (cont.)Modifications (cont.)

• Slicing the reconstruction kernel

ACSC’99 - An enhanced splatting method - Peter Kulka & Richard Lobb

High resolution splattingHigh resolution splatting

• Summary:

ACSC’99 - An enhanced splatting method - Peter Kulka & Richard Lobb

ComparisonComparison

• Test data set: CT scan of a human pelvis– Size: 256 256 110 sample points

ACSC’99 - An enhanced splatting method - Peter Kulka & Richard Lobb

ResultsResults

• Various rendering methods (close-up):

ray casting splatting high resolution splatting

ACSC’99 - An enhanced splatting method - Peter Kulka & Richard Lobb

ConclusionConclusion

• Three modifications to splatting:– Explicit volume reconstruction and illumination– Correcting of view angle distortions– Reconstruction along the line of projection

• Rendering times comparable to splatting

• Image quality comparable to ray casting

ACSC’99 - An enhanced splatting method - Peter Kulka & Richard Lobb

Future workFuture work

• More use of texture mapping hardware

• Perspective views

• Hierarchical versions– Building octrees– Wavelet splatting