NPR TodayStylized Rendering Techniques for Scalable Real-Time 3D AnimationPaper InformationSlide 4ContributionsStylistic ShadingSlide 7Slide 8Slide 9Slide 10Slide 11Slide 12Stylistic InkingStylized InkingSlide 15Slide 16Slide 17Slide 18Slide 19Motion LinesPerformanceSlide 22Future WorkQuestions?Slide 25“Computer-Generated Pen-and-Ink Illustration of Trees” (SIGGRAPH 2000)MotivationRelated WorkRelated Work ExamplesTraditional Illustration of TreesDrawing the SkeletonDrawing the FoliageDepth DifferencesDepth Differences Continued…Abstract Drawing PrimitivesLevel-of-AbstractionLevel of Abstraction Continued…Software ImplementationResultsSlide 40Slide 41Slide 42Sketchy DrawingsPrevious WorkAlgorithm OverviewG-BuffersEdge MapShade MapAdding UncertaintyEnd ResultStyle VariationsIssuesUpdating Depth InfoShower-Door EffectProcess SummarySlide 56Slide 5703/30/05 © 2005 University of WisconsinNPR Today•“Stylized Rendering Techniques for Scalable Real-Time 3D Animation”, Adam Lake, Carl Marshall, Mark Harris and Marc Blackstein, NPAR 2001•"Computer-Generated Pen-and-Ink Illustration of Trees", Oliver Deussen and Thomas Strothotte, SIGGRAPH 2000•"Sketchy Drawings", Marc Nienhaus and Jurgen Dollner, AfriGraph 200403/30/03 © 2005 University of WisconsinStylized Rendering Techniques for Scalable Real-Time 3D AnimationPaper OverviewLeo Chao03/30/03 © 2005 University of WisconsinPaper Information•Published–NPAR 2001•(Non-Photorealistic Animation and Rendering)–Authors•Adam Lake•Carl Marshall•Mark Harris•Marc Blackstein•Graphics Algorithms and 3D Technologies Group–Intel Architecture Labs•UNC – Chapel Hill03/30/03 © 2005 University of WisconsinPaper Information•Prior Work–No novel techniques, adapts from prior works to hardware•Motion Lines–Maic Masuch. “Speedlines: Depicting Motion in Motionless Pictures.” ACM SIGGRAPH 99 Technical sketch.–Siu Chi Hsu and Irene H. H. Lee. "Drawing and Animation using Skeletal Strokes". In Proceedings of ACM SIGGRAPH 94, pages 109-118. 1994.•Silhouette Edges–Lee Markosian, Michael Kowalski, Samuel Trychi, Lubomir Bourdev, Daniel Goldstein, and John Hughes. Real-Time Nonphotorealistic Rendering. In Proceedings of ACM SIGGRAPH 97, pages 113-122. 1997.•Cartoon Shading–Philippe Decaudin. Rendu de scenes 3D imitant le style dessin anime. Rapport de Recherche 2919, Institut National de Recherche en Informatique et en Automatique. 1996.03/30/03 © 2005 University of WisconsinContributions•Hardware Implementation of NPR Techniques–Stylistic Shading•Cartoon Shading•Pencil Sketch Shading–Stylistic Inking•Silhouette Edge Detection•Stylized Silhouette Rendering–Motion Lines03/30/03 © 2005 University of WisconsinStylistic Shading•Fundamentals–Preprocess colour textures–Render as normal–Except:•Modify lighting/shading calculations•May require texture coordinate processing•“Painter” – Modified Shading Step–Cartoon Shading–Pencil Sketch Shading03/30/03 © 2005 University of WisconsinStylistic Shading•Cartoon Shading–Reducing detail aids comprehension–No Smooth Shading•Color Reduction•Hard Transitions•Variants Simple03/30/03 © 2005 University of WisconsinStylistic Shading03/30/03 © 2005 University of WisconsinALGORITHM Cartoon ShadePreprocess:1. Calculate the illuminated diffuse color for each material:2. Calculate the shadowed diffuse color:3. For each material, create a texture with two colors- u=1 is coloured Ci- u=0 is coloured CsStylistic ShadingmlmlmgiddaaaaC mlmgsaaaaC Ci Vertex Color Cs Shadow Diffuse Coloral Light Ambient dl Light Diffuseam Material Ambient dm Material Diffuseag Coefficient of Global Ambient Lighting03/30/03 © 2005 University of WisconsinALGORITHM Cartoon ShadeRuntime:1. Calculate the one-dimensional texture coordinate at each vertex2. Render the model using a standard graphics API - Lighting disabled- Enable texture mappingStylistic Shading}0,{ nLMax L normalized light vectorn unit surface normal03/30/03 © 2005 University of WisconsinStylistic Shading•Pencil Sketch Shading–Extends cartoon shading to 2D textures–Extends cartoon shading to multiple textures–Multiple textures to represent light density–Associate texture coordinates•Project texture from the viewport onto the model03/30/03 © 2005 University of WisconsinStylistic Shading03/30/03 © 2005 University of WisconsinStylistic Inking•Fundamentals–Identify “important” edges•Silhouette•Border•Crease–Modify drawing of these edges•“Inker” – Modified Line Drawing–Visually important edge detection–Stylized edge drawing03/30/03 © 2005 University of WisconsinStylized Inking•Visually important edge detection–Silhouettes•Front-Face and Back-Face share an edge–Borders•Edge shared by two materials•Unshared polygon edge–Creases•Large dihedral angle between polygons03/30/03 © 2005 University of WisconsinStylized Inking03/30/03 © 2005 University of WisconsinStylized InkingALGORITHM SEDPreprocess:1. Create edge-list structure with Edge Type flagsa. Create a unique edge list using a hash table. b. Edge Hash Function: sum the two vertex indicesc. Border Flag-Edges with only one neighboring face-Two neighboring faces with different materialsd. Set crease flags-Non-deformable geometry-Dihedral angle of two faces > threshold03/30/03 © 2005 University of WisconsinStylized InkingALGORITHM SEDRuntime:1. For deformable meshes:a. Calculate face normalsb. Detect crease edges from face normalsc. Set Crease Edge flags2. Detect silhouette edges a.03/30/03 © 2005 University of WisconsinStylized Inking•Stylized “Important” Lines–Emphasis on these lines–Option 1: Straight Line•Fast/Easy–Option 2: Texture Maps•“Artistic” Style•Curvature driven “strokes”•Involves a graph driven search•This is a HACK03/30/03 © 2005 University of WisconsinStylized Inking03/30/03 © 2005 University of WisconsinMotion Lines•Gives the appearance of motion•For fast moving objects•Simple algorithm•Not much overhead–One circular buffer to maintain position data03/30/03 © 2005 University of WisconsinPerformance•Claim: Maintain Real-Time Speeds–30 fps, in 2001•Tests:–Integrated with a level of detail scheme–Altered model complexity to maintain FPS03/30/03 © 2005 University of WisconsinPerformance03/30/03 © 2005 University of WisconsinFuture