Your Depths

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AIC 2008Defining 3D Astronomical ImagingV1.1 November 2008AIC 2008


Movement Zones (RMZ, SMZ, IMZ)Observer positionStars spaced along the line of sightToo close to objectTarget objectReal Observer(You)RealisticMovement Zone(RMZ)The camera can be moved to anyvantage point without losing thevisual fidelity of the original imageSpeculativeMovement Zone(SMZ)Visual fidelity starts to break downbut full data accuracy is still possiblethrough physical models andreasoned assumptionVirtualObserverImaginary MovementZone (IMZ)The camera moves too far beyondwhat can be observed from Earth soimagination must fill in the gapsV1.1 November 2008AIC 2008


3D Astronomical Visualization“To create accurate 3D representations ofastronomical objects and their environmentsthat are spatially and geometrically accurate,visually faithful to the original image, and canbe visualized from alternative viewpointsthrough still images, animation, andstereoscopy”V1.1 November 2008AIC 2008


So…. Explore your depthsStephan’s Qunitet: Hybrid rendered image. (Author: Wide field star-field, selected galaxies, Gemini 8 meter: NGC7320, other galaxies)V1.1 November 2008AIC 2008


AIC 2008Fundamental TechniquesV1.1 November 2008AIC 2008


Analyzing astronomical depth cuesObvious Foreground ObjectsOcclusions: Foreground objects that block othersAngle of observed object: Correct proportions canbe derived from similar typesSource:Hubble Gallery – Interacting Galaxies AM 0500-620Source:Hubble Gallery – M17Perceived Detail: Closer objects show more detailthan distant onesBoundary crossing elements (Gas/Dust) thatcontinue across multiple objectsCentral directional lighting: defines shapeV1.1 November 2008AIC 2008


Misleading astronomical depth cuesNon-Directional (emission nebula) lighting definesdetail but not necessarily the true shapeShading provides clues to shape and form but isnot comparable to a solid objectOther missing cues:Absence of binocular disparity (But can besimulated)Absence of proper motion derived depth cues(Except for very close objects over yearsSource: Hubble Gallery – M16V1.1 November 2008AIC 2008


Separating the visual elements of an image• Photoshop Methods• Selection Toolset (Color Range etc)• Repair with Color Replacement, Healing,Clone Brush etc• A lot of copy and paste!• Camera Filter Methods• Narrow band filters reveal different levels ofstructural detail• Continuum filters to remove non-required data• Plate Solving methods• 3D Paint &Compositing Methods• Z-depth layering of specific elements• Depth mapsV1.1 November 2008AIC 2008


Applying distance data to scene elements• Sources of astronomical distance data• Ground or satellite based parallax measurements• Physical modeling from parameters such as size,mass, angular distance etc• Stellar photometry data• Standard Candles• Cosmological Red Shift data• CephidsCombining distance data with scene elementsenables the simulation of a virtual 3D universeboth along and off the line of sightV1.1 November 2008AIC 2008


A 3D rendering primer1 Modeling 2 Animation 3 Rendering 4 Post-ProductionObjects in the scene are createdand positioned in spaceThe camera and the objects in thescene are animatedShaders and lights are applied and thescene is rendered frame by frameThe rendered frames are composited,recorded to video etc…Creating ShadersTextures are created from sourceimagesDisplacements (If needed) arecreated from source imagesDisplacementThe shaders are test rendered beforeapplication and final renderingLights are created and positionedaround the objects in sceneV1.1 November 2008ShaderAIC 2008


The Famous Teapot Nebula (Fake!)Rendered with Aqsis to the RenderMan standardV1.1 November 2008AIC 2008


4 methods for simulating 3D depth2D Multi-Plane Rendering:2D layered image planes scaled and panned tosimulate 3D in a non-perspective environment3D Multi-Plane Rendering:2D image planes arranged or animated in a 3Denvironment with full perspective*3D Multi-Plane Displacement Mapping:3D detail extracted from 2D image planes in a 3D perspectiveenvironment3D Forced Perspective Rendering:Simulating 3D by warping 2D image planes in 3D space tocreate the illusion of parallaxV1.1 November 2008*AIC 2008


AIC 2008Source image:Starfield and QuintetChris Ford (Author)Other Quintet and NGC73208 Meter Gemini3D Multi-Plane RenderingV1.1 November 2008AIC 2008


Stephan’s Quintet describedNGC7317c. 347 MLYNGC7320c. 41 MLYNGC7318Ac. 349 MLY(Tidally Disrupted)Tidal Tail ripped out byNGC7320C(Off Image)NGC7318Bc. 304 MLY(Passing Through)NGC7319356 MLYStarfield(In Milky Way)Source Image: GEMINI 8 Meter TelescopeV1.1 November 2008AIC 2008


Dissecting the image into separate elementsForeground Star Field Tidal Tail NGC7320 NGC7318bNGC7318a NGC7319 NGC7317• Components separated into Texture Map layers in Photoshop• Grayscale Opacity maps derived from Texture Maps• Foreground star-field imaged by author (For sufficient camera motion space)V1.1 November 2008AIC 2008


Spacing scene elements for depthOrthographic CameraAnimated Line Of SightTexture Map controlsfinal image color and detailKey Frame TimelineOpacity Map controlsimage plane transparency• Separated image elements texture mapped onto image planes• Image planes spaced from camera (along Z-Axis) by red shift distance data• (Spacing shown above is for illustration and not to scale)V1.1 November 2008AIC 2008


A Journey to NGC 7320 (And Back)V1.1 November 2008AIC 2008


AIC 2008Original image data:Chris Ford (Author)3D Multi-Plane Displacement MappingV1.1 November 2008AIC 2008


Displacing the Crab Nebula• Displaced surface• Regular diffuse lightingavoids inaccurateshading artifacts• Color image is texturemapped onto the displacedsurface• Grayscale image drivesvertical displacement ofgeometry normal to thesurface orientation• White = High• Black = LowSource images: Chris Ford (Author)Animation of the Displacement Scale Factor• Crab Nebula Assumptions• Cloud topography is illuminated from acentral point light source• Obvious occlusions show depth orderof image elementsV1.1 November 2008AIC 2008


Squeezing 6500 light years in your computerStarfieldMulti-PlanesCameraFrustrumCameraDisplacement PlaneV1.1 November 2008AIC 2008


Animating the Crab• Wide field star-field imaged separately and combined and aligned in 3D• Camera traverses a “constrained” baseline 8 Light years acrossV1.1 November 2008AIC 2008


Integrating Hubble data…• HST image displaced and combined with star field imaged by author• Crab split into multiple displaced layers to illustrate interior luminosityV1.1 November 2008AIC 2008


AIC 2008IC1396 (3D reconstructionfrom an original source image byNeil Fleming)3D Nebula Rendering (1)V1.1 November 2008AIC 2008


Analyzing a nebula image (M17)Source: Hubble Gallery – M17Ultra violetradiation from hotyoung stars (offimage) providesdirectional lightingfor displacing gasand dust cloudsForeground starsBackground nebulastructure (2)Semi-Transparentgaseous and dustveil (Streaming offthe gas and dust)forms a translucentlayerOccluded nebulalayers sculpted byultra-violet radiationfrom top leftBackground nebulastructure (1)Occluded nebulalayer boundarycloser to observerTotal: 2 star layers, 5 foreground nebula layers, 1 semitransparentveil, 2 background nebula layers, 1 farbackground layerV1.1 November 2008AIC 2008


Reconstructing 3D depthDisplaced image layers are spacedalong the Z-Axis• Image width is 3 light years• Camera traverses orbital path 1 light year in diameterSide view of displaced multi-planesillustrating build up of depthV1.1 November 2008AIC 2008


Nebula case study 1 - IC 1396IC1396 source imagecourtesy of Neil FlemingExisting images can be processed into 3D!V1.1 November 2008AIC 2008


Nebula case study 1- analyzing IC1399Narrow band Source image: Neil FlemingV1.1 November 2008Multiple gas/dust occlusionlayersWispy dust tendrils“Hollowed” area receding fromobserverHa Source image: Chris Ford• Ridiculous numbers of stars!• Star density of 40 visible starsper 100 pixels square average• Star density analysis reveals c.25,000 stars in whole imageAIC 2008


Nebula case study 1 - element separationMask1: Displaysforeground nebulaelementsOriginal imageMask2: Displaysmiddle ground nebulaelementsMask3: Displays backgas and dust elementsBackground image with stars andupper layers removedGrayscale for displacements(White = further away)V1.1 November 2008AIC 2008


Nebula case study 1 - IC1396 test renderingTotal star count under-sampled (Smallest stars removed to reveal nebula detail)V1.1 November 2008AIC 2008


The problem section!• Scintillating stars as they pass over each other• Bloated stars• Over exposed stars look horrible when you get too close• Limitations on getting close due to low resolution• Color bleeding from stars into background objects and viceversa• Photoshop processing artifacts• Noise in image obscuring faint background detail• Lack of intuitive reference objects for proper depth perception• Intergalactic objects can be hard to orient yourself toV1.1 November 2008AIC 2008


AIC 2008Globular ClusterSimulation combinedwith M13 star field3D Star Rendering TechniquesV1.1 November 2008AIC 2008


3D star rendering - layer methodsZ-Axis Multi Plane Star MappingThe “Star Lens” MethodIndividual stars can be mapped at correctdistance along Z-AxisClosely packed curved star planes with starsdisplaced into interior volume• Suitable for stars with known distances• Suitable for foreground stars when targetobjects are very distant (ie: galaxies)• Ideal for large clusters of stars where individualdistances are unknown or approximately the same• Need minimum 5 closely spaced planes to achieverealistic distributionV1.1 November 2008AIC 2008


3D star rendering - particle substitution• A star-field texture can be used toemit particles• Each white star emits one particlenormal to the texture surface sothat visual alignment with theoriginal image is maintained• Each particle is sized according tothe FWHM of the original star• Each particle is displaced a randomdistance along the normal for realisticdepth spacing, OR assigned a realdistance where known• Each particle inherits the color of theoriginal star• Particle stars are rendered withrealistic glowsV1.1 November 2008AIC 2008


3D Star Rendering – growing globs• The 3D form of globular clusters can be predicted• Distribution of stars in this image of M13 determined bystatistical analysis of color and visual density• Globular “grown” from particle stars released and bound intoa simulated gravity field60% white stars30% red stars10% blue starsM13 SimulationV1.1 November 2008AIC 2008


AIC 2008IC1396 (3D reconstructionfrom an original source image byNeil Fleming)3D Nebula Rendering (2)V1.1 November 2008AIC 2008


Nebula rendering with star substitution (1)Soft star rendering – fully sampled original imageV1.1 November 2008AIC 2008


Nebula rendering with star substitution (2)Added star glowV1.1 November 2008AIC 2008


Case study 2 - Tarantula NebulaLarge numbers of foreground starsWell defined nebula occlusionsCentral illumination defines shapeHuge numbers of dim backgroundstarsSource Image: NGC 2070 Tarantula Nebula, Courtesy of R Jay GabanyV1.1 November 2008AIC 2008


Nebula case study 2 - element separationImage texture with stars extractedOriginal image„ 5 Foreground Star Layers„ 1 Nebula Layer„ 3 Background star layers„ Animation Camera„ Camera orbital motion pathV1.1 November 2008Arrangement of image elementsAIC 2008


Nebula case study 2 – orbiting the TarantulaV1.1 November 2008AIC 2008


What tools do I need?• A Paint Application• For separating image elements into layers• For creating stereoscopic still images• Recommendation: Photoshop• A 3D Application• For positioning scene elements in 3D space• For establishing alternate camera view points• For creating video and stereoscopic animation• Recommendation: Maya, 3ds max, XSI, Cinema4D, Hash,Blender etc• A Editing and Compositing Application• For editing, assembling, and outputting animation• For creating stereoscopic animation• Recommendation: After EffectsV1.1 November 2008AIC 2008


AIC 2008StereoscopicAstronomicalImagingV1.1 November 2008AIC 2008


Stereoscopic viewing methods• Cross your eyes!• Anaglyph Glasses• Shutter Glasses• Shutter Glasses and Projector• Polarized Projection• Head Mounted Displays• Lenticular/Barrier TFT• All sorts of strange devices…!V1.1 November 2008AIC 2008


Simple stereoscopic cinematographyToe-In Cameras• Toe-in cameras• Positive parallax• Objects appear behind the screen• Requires tweaking to avoid trapezoidaldistortion• Not recommended for astronomicalobjects except extreme close ups, closefly bys, and zoom shotsParallel Cameras• Parallel cameras (Recommended)• Negative parallax• Objects appear in viewer space or infront of screen• Easy to set up by simply displacingcamera along X axis (It’s how your eyeswork)• Suitable for most astronomical objectsV1.1 November 2008AIC 2008


A sample stereoscopic anaglyphLeftInter-Ocular rule of thumb• 30 to 1 rule• Image offsets < 15%Right• Inter-Ocular Distance = 120,000 Light Years! CORRECT – 3D is BACK TOFRONT!V1.1 November 2008AIC 2008


Creating anaglyphs in Photoshop• Open separatelyrendered Left andRight images• “Select All” in leftimage• “Copy” (left image)Red Channel and“Paste” into (rightimage) Red Channel• Select RGBChannel and testwith 3D effect withanalgyph glasses• If 3D is “inside out”paste Right into Leftor reverse theanalglyph glasses• Inter-Ocular Distance = 120,000 Light Years! CORRECT – 3D is BACK TOFRONT! Paste left Red Channel into Right Red ChannelV1.1 November 2008AIC 2008


Creating stereo animation in After Effects• Separately render Left and Right animation frames of the object• Use After Effects to merge Left and Right sequences and test the resultsUse “3D Glasses” in Effects->PerspectiveSelect Red Channel and Right RedChannelExperiment with the image convergencewearing anaglyph glassesTest at full resolution. Swap Left andRight if positive parallax results(Objects inside out)Export in desired formatV1.1 November 2008AIC 2008


Put on your 3D glasses!Left Eye = RedRight Eye = BlueV1.1 November 2008AIC 2008


The “Coming right at ya” shot!”V1.1 November 2008AIC 2008


Stereo rendering with displacement maps (1)V1.1 November 2008AIC 2008


Stereo rendering with displacement maps (2)V1.1 November 2008AIC 2008


Nebula rendering in stereo (IC1396)Original stars - SampledV1.1 November 2008AIC 2008


Nebula rendering in stereo (IC1396)All stars present via particle substitutionV1.1 November 2008AIC 2008


Summary• 3D astronomical imaging is a synthesis of imaging, processing,current knowledge, real data, theory, interpretation, andcreativity• The flood of data anticipated over the next decade requires amore sophisticated display format• The tools are accessible to anyone who has masteredPhotoshop and other image processing applications• It is an ideal medium to interpret objects and vistas in a mannermore intuitive to the human visual system• Parallels the ongoing evolution in display technologies that willbe accessible to the consumerV1.1 November 2008AIC 2008


AIC 2008EndContact: cford81@comcast.netV1.1 November 2008AIC 2008

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