1. HSR & Scan conversion
신승영

2. Hidden Surface Removal
Whenever a picture contain opaque objects, those that are closer to the viewer and in the line of sight of other objects will block or occlude those farther objects from view. Blocked or hidden surfaces must be removed to provide realistic images

3. HSR - Object Space Object Space
Considering the objects pairwise, as seen from the center of projection computation done in object coordinates at object precision level.
Loop :
compare( object_k, object_k-1)

4. HSR – Image Space Image Space Follow our viewing and ray-casting model
Consider a ray that leaves the center of projection and passes through a pixel

5. HSR – Back Face Removal Back Face Removal
For a polygonal model, we see the front of a polygon if the normal, which comes out of the front face, is pointed toward the viewer.

6. HSR – Z buffer Removal Z-buffer Removal
Storing a depth value at every pixel
Maintain two screen sized arrays
Color buffer for storing color value for each pixel
Depth or z-buffer for shorting nearest polygons

7. Scan Conversion Definition Problem
Specification of geometric entities in an application program to the setting of pixel in the frame buffer.
Problem
Compute value : real numbers
Display value : fixed numbers

8. Scan conversion - DDA Method Advantage : easy
Get slope
Round other value
Advantage : easy
disadvantage : real numbers calculations
for( ix = x1; ix<=x2; ix++) {
y += m
write_pixel( ix, round(y), line_color); }

9. Error of DDA
Inversed Slope

10. Bresenham’s Algorithm
Avoids all floating-point calculations
Standard algorithm used in hardware and rasterization.

11. Bresenham’s Algorithm
d = b-a
d < 0 : lower pixel
d > 0 : upper pixel

12. Bresenham’s Algorithm

13. Antialiasing Polygons look jagged Cause The number of pixels is fixed
Pixel locations are fixed on a uniform grid
Pixels have a fixed size and shape
Aliased line segment
Anti-aliased line segment
Ideal raster line

14. Dithering and Halftoning
원래는 더 많은 색상으로 되어 있던 영상을 제한된 더 적은 색상으로 표현하기 위한 방법
Halftoning
검정색과 하얀색을 섞어서 회색을 표현하는 방식
Digital halftone patterns