![Cont…
– Step 4: Reorder the face and priority
lists so that the highest priority is on top
of the list.
– In this case, the face and priority lists
are [F1, F2, F3, F4, F5, F6] and [1, 1, 1,2,
2, 2], respectively.
– Step 5: In the case of a raster display
hidden line removal is done .
– Step 6: In the case of a vector display
the hidden line removal must be done
by the software by determining
coverings.](https://image.slidesharecdn.com/visualrealismhiddenremoval-180902020031/85/Visual-realism-HIDDEN-REMOVAL-METHODS-23-320.jpg)
Visual realism -HIDDEN REMOVAL METHODS
- 1. ME 6501 COMPUTER AIDED DESIGN Unit 3: visual realism By Viswaaswaran.J 16me105 III MECH-C
- 2. CONTENTS HIDDEN LINE REMOVAL HIDDEN SURFACE REMOVAL HIDDEN SOLID REMOVAL
- 3. VISUAL REALISM – Visual Realism is a method for interpreting picture data fed into a computer and for creating pictures from difficult multidimensional data sets. – It is technique for creating images or animation to communicate ideas.
- 4. What is the need of visualization? – The need of visualization is to convert 3D data in 2D screen. – The basic problem of the visualization is how to display 3D data on a 2D screen. Visualization Geometric Techniques Scientific computing
- 6. Problems in visualization – 3D models are used to create the visual real effect. – The object may consist of number of vertices, edges, surfaces which are represented realistically in 3D modelling. – Projection 3D object into 2D screen displays the complex lines and curves which may not give a clear picture to interpret.
- 7. Algorithms – To eliminate the problems we use algorithms. – Algorithms eliminate the ambiguities of rendering 3D models and are considered the first step towards the visual realism – ALGORITHMS TOWARDS VISUAL REALISM – HIDDEN LINE REMOVAL – HIDDEN SURFACE REMOVAL – HIDDEN SOLID REMOVAL
- 8. REMOVAL ALGORITMS – Removal algorithms are classified into hidden line and hidden surface algorithms. – There are two types of displays raster and vector displays
- 9. Cont… – The hidden line removal deals with the visibility problem of edges of polyhedral models; these are models with orientable flat polygon faces. – The hidden surface removal with the visibility problem of edges of polyhedral models; these are models with orientable curved surfaces.
- 10. Classification OBJECT SPACE METHOD. It compares the object and the parts to rach other within the scene definition to determine which surface are visible IMAGE SPACE METHOD The visibility is decided point by point as each pixel position on the view plane
- 12. Minimax test
- 13. Cont…
- 14. Containment test
- 15. Cont…
- 16. Cont…
- 17. Cont…
- 18. Cont..
- 19. sillhouettes
- 21. Hidden line removal Priority Algorithm – This algorithm is also known as Depth or Z algorithm. – This algorithm is based on sorting all the faces in the scene according to the largest z coordinate. – Step 1: Utilize the proper orthographic projection to obtain the desired view(whose hidden lines are to be removed) of the scene. – Step 2: Utilize the surface test to remove back faces to improve the efficiency of the priority algorithm.
- 22. Cont.. – Step 3: Assign priorities to the faces in the face list.
- 23. Cont… – Step 4: Reorder the face and priority lists so that the highest priority is on top of the list. – In this case, the face and priority lists are [F1, F2, F3, F4, F5, F6] and [1, 1, 1,2, 2, 2], respectively. – Step 5: In the case of a raster display hidden line removal is done . – Step 6: In the case of a vector display the hidden line removal must be done by the software by determining coverings.
- 25. STEPS INVOLVED 1. Identify the silhouette polygon 2. Assign quantitative hiding values to silhouette polygons. 3. Determine the visible silhouette segments. 4. Visible silhouette segments with partially visible face. 5. Display the interior partially visible polygons.
- 27. Cont…
- 28. Hidden Surface Removal – Hidden surface algorithm uses image –space techniques. Types of algorithms Z-Buffer algorithm. Watkin’s algorithm (scan line coherence). Warnock’s algorithm (area coherence). Painter’s algorithm (priority algorithm).
- 30. Z-BUFFER
- 33. Cont…
- 34. Warnock’s Algorithm – 1. Surrounding Polygon - One that completely encloses the (shaded)area of interest – 2. Overlapping or Intersecting Polygon - One that is partly inside and partly outside the area – 3. Inside or Contained Polygon - One that is completely inside the area – 4. Outside or Disjoint Polygon - One that is completely outside the area
- 40. RAY TRACING
- 46. THANK YOU