Visible surface detection methods
- 2. Classification of Visible Surface Detection Algorithms 1) Object-space Methods: Compare objects and parts of objects in a scene and to determine which surfaces are visible in a scene.
- 3. Classification of Visible Surface Detection Algorithms 2) Image-space Methods: Visibility is determined point by point at each pixel position on the scene.
- 4. 1) Painter's Algorithm Painters paints the distant parts of a scene before parts which are nearer thereby covering some areas of distant parts.
- 6. ALGORITHM FOR PAINTERS ALGORITHM 1) Sort al the Polygons in the decreasing depth. 2) If overlap is detected in the polygon it must be sorted net.
- 7. 2) Binary space partitioning Alg It is defined as “polygon is drawn if all the polygons which is away from the viewpoint is drawn first, then the polygon which is closer to the viewer is drawn next”.
- 8. Binary space partitioning Alg 1) Find the distance of position Camera 2) If the distance is greater than 0 then a. Go to Back node b. Note down the polygon vertices 3) If step 2 is false then a. Go to Front node b. Note down the polygon vertices
- 9. 3) Back Face Detection In an object, there are 2 surfaces namely Front face and Back faces. Each surface has a vector. If this vector is pointing in the direction of the center of projection, it is a front face and can be seen by the viewer. If it is pointing away from the center of projection, it is a back face and cannot be seen by the viewer.
- 11. A BUFFER METHOD Each position in the A-buffer has 2 fields Depth field − It stores a positive or negative number Intensity field − It stores surface-intensity information
- 12. A BUFFER METHOD
- 13. A BUFFER METHOD If depth >= 0, It is a single surface. The intensity field stores the RGB components of the surface color at that point and the percent of pixel coverage. If depth < 0, it indicates multiple surface. It also includes 1)RGB intensity components 2) Depth 3) Percent of area coverage