ERC Expressive Seminar

Transcription

1 ERC Expressive Seminar March 7th Models and Intuitive Modeling Loïc Barthe VORTEX group IRIT Université de Toulouse

2 Plan Context and introduction Intuitive modeling Modeling with meshes only Other representations then meshes Sketching On an ideal system? Well some insights... But what about highly complex topology and more general objects? Conclusion

3 Displays / 3D Printers => 3D content => Geometric modeling

4 What to avoid for a modeling session? Boring and fastidious No undo and unpredictable Complex and non-intuitive

5 Intuitive modeling? Ideally System fonctionnalities fast and easy to learn / understand Shape corresponding to user expectations when responding to user input Freedom in shape variety Obvious construction of the modeling process Accessible interaction Fast object creation Interactive feedbacks

6 Surface Properties Ideally Continuity : C0, C1, C2, Oscillations only if desired Planar or not Different level of details Fair / elegant Arbitrary genus

7 Triangle meshes Fast and easy rendering of 3D objects require the use of triangle meshes Virtual environments are essentially composed of triangle meshes

8 Triangle meshes Whatever the modeling process, at the end, we want the surface to be fairly represented by a mesh, preferably 2D Manifold

9 Surface = a 2D Manifold Mesh What it is good for : Fast rendering Represent complex objects Multi-resolution modeling Subdivision Simplification Deformations Control net Smooth surface Finite element Parametrizable Remeshing Material

10 Surface = a 2D Manifold Mesh What it is NOT good for : Changes in object topology In/out queries Collisions Inter-objects self-intersections CSG Highly deformable objects Fluids

11 Meshes and Geometric Modeling Non dedicated software Total freedom But : Blender 3DS Max Maya

12 Meshes and Geometric Modeling Dedicated software Dedicated to a specific context User friendly => Mostly planar surfaces User friendly => Organic / Smooth surfaces SketchUp Sculptris Meshmixer

13 Mesh from another representation Dedicated software Dedicated to a specific context User friendly => Organic / Smooth surfaces Teddy - sketching Z-Brush - Z-Sphere

14 Zoom : Z-Brush vs Sculptris Prototyping : Z-Spheres Intuitive modeling vs Large deformations Complete Surface properties Intuitive modeling Shape thickness Surface properties Globally C2 continuous Continuity C>0 Genus? Genus 0

15 Zoom : Z-Brush vs Sculptris Detail modeling with brushes and mesh deformations : Subdivision surfaces Intuitive modeling Local remeshing Becomes complex Surface properties vs Complete Intuitive modeling Becomes complex Surface properties Continuity C>0 Genus 0

16 Zoom : Z-Brush vs Sculptris Detail modeling with brushes and mesh deformations : Subdivision surfaces vs Local remeshing Quads Triangles Multiresolution Adaptive resolution Sharp edges Sharp edges Isotropic refinement Anisotropic refinement

17 And Sketching? Surface reconstruction from contours Teddy's process : contour => chordal axis => Mesh Incrementally add new object parts Prototypes, Smooth surfaces

18 Sketching + Implicit Surfaces Surface reconstruction from contours General process : contour => chordal axis => Implicit Surface => Mesh => Prototypes, Smooth surfaces Advantages : => Arbitrary genus Easier and more stable implementation Composition operators Oscillations hard to avoid Surface deformations non trivial But

19 Implicit Surfaces Different families of field functions RBF = contour + additional points + normals HRBF = contour / lines (unorganized) + normals Soft Objects = contour + medial axis Oscillations Thickness hard to control Convolution Surfaces = contour + medial axis Oscillations Thickness hard to control But for oscillations : But for thickness : Triangle skeletons Radially varying radius

20 Implicit surfaces in general What they are NOT good for : Fast rendering Represent complex objects Multi-resolution modeling Subdivision Simplification Deformations Control net Smooth surface Finite element Parametrizable Remeshing Material

21 Implicit surfaces in general What they are good for : Changes in object topology In/out queries Collisions Inter-objects self-intersections CSG Highly deformable objects Fluids Represent smooth surfaces Automatic thickness

22 An ideal system? Z-spheres vs sketching The first is the user providing the beginning of the reconstruction for the second Could work together? «Dog Labrador drawing» in google image :

23 An ideal system? Accept more approximative reconstruction Oscillations Fairness Deformations for shape adjustment Deformations for pose adjustment Skinning at joints Contact deformations Non centered skeleton Use animation skeleton to enable pose modification and skinning

24 An ideal system? But also, what about Mindcraft Blocks

25 An ideal system? Blocks / skeletons of different forms (cubes, cylinders, spheres, others?) Implicit surfaces for reconstructing the surface with a correct topology High quality approximation with a mesh

26 Conclusion An ideal solution : nothing obvious Apparently, different models / interactions for different steps : prototype / adjustment / details Sketching is the solution : it is one, but I guess, not alone Z-Spheres : not really explored => nothing else to do? Explore other ways for building a 3D object Intuitive modeling is still an open problem

27 Questions

28 Implicit surfaces Can they compete with meshes? In general : NO Is there an interest to use them alone? Yes for volume manipulation Yes for fluid rendering Yes for representing highly dynamic objects changing topology Yes for fast prototyping by sketching Otherwise No. But why not mixing meshes and implicit surfaces? Good suggestion but It is a complex problem Several moderatly successful attempts in the years around 2000 Recent works on skinning will maybe be a first step.

29 Implicit surfaces What could I expect from an efficient and effective research? TO DO Fast rendering Fine details representation Parametrization Efficient dual mesh/implicit-surface representation Would allow you to end up with A robust functional representation An efficient high level model for mesh generation, deformation and topology modifications

30 Parametric patches They will not help you : They share the same limitations They have aditional limitations