1. Modeling, CG, and others Jyun-Ming Chen Fall 2001

2. Contents Modeling geometric modeling model segmentation LOD Image-based vs. geometry-based systems Primers on Computer Graphics Kinematics

3. Geometric Modeling how 3D objects are described in the geometric database shape primitives: box, cylinder, sphere, cone, indexed face set  watch for the face orientation (used for backface culling) procedurally defined shape: extrusion, sweep, in rendering, all objects are converted to triangles

4. Computer Graphics Primer

5. Animation displaying a sequence of rendered scenes frame rate: number of scenes displayed per second movie: 24-30 NTSC: 29.97 VR: at least 16 to be flicker-free; the higher the better factors affecting frame rate size of rendering area model complexity: retrieving, rendering hardware displaying/shading mode

6. Model Segmentation especially important for walkthrough applications in a large geometric database 1-500 million polygons; 10 frames/sec

7. Cell Segmentation manage model complexity by grouping objects visible from different rooms Leaf nodes store corresponding links to visible objects Visibility problem auto-segmentation separating plane priority priority = 0.5*occlusion + 0.3*balance + 0.2*split

8. Level of Detail (LOD) Change based on: distance or image size multi-resolution model automatic model simplification  Borrel & Rossignac (92)  Edge Collapsing  …

9. LOD (cont) Model flickering problem: Hysteresis Model morphing Mipmap: LOD concepts applied to texture mapping Implement this in VRML Proto

10. Rational Reducer (Systems in Motion) Price: 4,950 USD !!

12. Generating Mipmaps

13. Image-based VR compared to “ geometry-based ” VR able to keep constant frame rate regardless of the scene complexity authoring tools camera setup procedure “ hybrid ” -VR

14. Image Acquisition

15. Image Warping

17. Stitched Panorama

18. Kinematics Primer

19. Kinematics in VRML Syntax of Transform Node (partial) usually interpretation using local axes is easier the two-link arm in VRML take advantage of “ short hand notation ” center t + r explore other fields (scale, scaleOrientation) on your own

20. Transform in VRML97

21. Exercises sketch the 3D model of the given VRML file Biped model: Construct each rigid part at default position Use transform to take them to due places Animate joint angles using OrientationInterpolators Coordinate your animation using ScalarInterpolators