Image Synthesis. Fur Rendering. computer graphics & visualization

Transcription

1 Image Synthesis Fur Rendering

2 Motivation Hair & Fur Human hair ~ strands Animal fur ~ strands

3 Real-Time CG Needs Fuzzy Objects Name your favorite things almost all of them are fuzzy!

4 Motivation

5 Previous work on fur Particle systems [Reeves 83] Volume textures [Kajiya & Kay 86] Special surface shader [Goldman 97] Geometry [Van Gelder & Wilhelms 97] Volume textures using CG Hardware [Meyer and Neyret 98] [Lengyel 00]

6 Geometric Models Cones too slow on current hardware Lines interactive for sparse fur Poor filtering

7 Previous work on fur Volume textures using CG hardware [Meyer and Neyret 98] Shell textures [Lengyel 00]

8 Shell Textures

9 Shell Textures Shells: Extrude model outwards and texture each shell it with progressively higher slices from a 3D fur texture

10 Generating the Textures Geometric model Seed surface with curl starting points. Grow as particle system

11 Generating the Textures Interpolate to generate more seed points. Ignore hair-to-hair collision.

12 Generating the Textures Sample volume Keep: Color Opacity (normal)

13 Generating the Textures Wide range of fur possible with different seed colors and curl parameters

14 Problems with shell textures (1) Surface parametrization (given arbitrary surface)? (2) Texture memory usage (several shells, over entire surface, at hair resolution!) lapped volume textures

15 Problems with shell textures (3) Poor silhouettes (shells break apart at oblique angles) fin textures

16 Review of Lapped Textures surface texture patch

17 Key Idea: Patch Pasting surface texture patch

18 Lapped volume textures Simple idea: each shell is a lapped texture. opaque skin transparent shells composite

19 Issues Rendering order innermost outermost shell Texture alpha Lapped textures: splotch outline Volume is semi-transparent alpha = splotch outline volume alpha

20 Poor silhouette offset shells original mesh

21 Fins offset shells original mesh extruded fin

22 Fin Textures skin & shells fins skin, shells & fins

23 Fin Texture Single fin texture Interval region for each edge. edge2 edge1

24 Fin rendering Rendering order: skin fins shells shells, fins : no Z buffer write! alpha blending Fade static fins based on viewing angle (or use a geometry shader to create fins on the fly)

25 Results