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Introduction to Scientific Visualization

CS 4390/5390 Data VisualizationShirley Moore, Instructor

October 13, 2014

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SciVis aka Spatial Data Visualization

• SciVis emerged as a discipline in the 1980s in response to the large amount of data produced by numerical simulations of physical phenomena (e.g., fluid flow, heat convection, material deformation).

• Primary concern is visualization of 3D phenomena with emphasis on realistic renderings of volumes, surfaces, illuminations source, etc.

• Depiction of datasets that have a natural spatial embedding• Relies heavily on computer graphics• Reference: Data Visualization: Principles and Practice, by

Alexandru Telea, 2nd edition, CRC Press, 2014.

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SciVis Pipeline

Image credit: Alexandru Telea, Data Visualization: Principles and Practice, 2nd edition

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DataSet

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Simple Example: Visualization of a Scalar Function of Two Variables

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Sample 1: Single-color Gridded Surface

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Sample 1 Code in C++ and GLUT

• sample1.cpp• What happens if we use fewer sample points?• Viewpoint of virtual camera

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Sample 2 Plot))2^2^/(1sin()( yxxf

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Rendering Equation

• Describes relationship between incoming light, outgoing light, and material properties at a given point

• Approximate lighting effects to varying degrees of realism

• Global illumination methods– radiosity methods– ray-tracing methods

• Local illumination methods– Phong lighting model

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Phong-Blinn Lighting Model

• Bui-Tuong Phong, “Illumination for Computer-Generated Images”, 1973

• Jim Blinn, “Models of Light Reflections for Computer Synthesized Pictures”, 1977

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Phong-Blinn Lighting Model (2)

Image from Wikipedia

Phong lighting equation:I(p, v, L) = camb

Il(cdiffmax(-L . n, 0) + cspecmax(r . v, 0)α)

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Phong Lighting Model in OpenGL

• With flat shading: sample3.cpp• With Gouraud shading: sample4.cpp

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Transparency

• Draw domain grid: sample5.cpp• Draw elevation plot with transparency factor:

sample6.cpp

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Texture Mapping

• Map 2D texture image onto 3D elevation plot• Sample7.cpp

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ParaView

• http://www.paraview.org/ • Open source tool for scientific data visualization• Collaborative project between Kitware, Los Alamos National

Lab, Sandia National Lab, and Army Research Lab• Can run in parallel to process large datasets• Built on top of the Visualization Toolkit (VTK), which is a

portable open source C++ library for computer graphics and visualization– http://www.vtk.org/

• Flat and Gouraud shading examples in ParaView:– Gaussian (flat).pvsm– Gaussian (Gouraud).pvsm

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Preparation for Next Class

• Finish Lab 3• Study for quiz