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Circle & curve clipping algorithm
This document discusses algorithms for clipping circles and curves to a bounding region. It describes a fast circle clipping algorithm that uses an accept/reject test to determine whether points are inside or outside the clipping region. It also discusses a midpoint circle algorithm that uses incremental steps to scan convert circles. Finally, it explains that curved objects can be clipped by first testing if their bounding rectangles overlap the clipping region before solving nonlinear equations to find curve-window intersection points.
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Circle & curve clipping algorithm
- 1. Circle & CurveClipping AlgorithmPresented By : Mohamed El-Serngawy
- 2. OutlineFast Circle Clipping AlgorithmClipping Circle By Accept/Reject Test
- 3. Fast Circle Clipping AlgorithmIntroduction:
- 4. Fast Circle Clipping AlgorithmAlgorithm
- 5. Fast Circle Clipping AlgorithmAlgorithm
- 6. Fast Circle Clipping AlgorithmAlgorithm
- 7. Fast Circle Clipping AlgorithmAlgorithm
- 8. Fast Circle Clipping AlgorithmAlgorithm
- 9. Clipping Circle ByAccept/Reject Test1-Scan Conversion of Circles 2-Write Points(x,y)3-Clipping Circles
- 10. MidpointCircle AlgorithmChoose E as the next pixel if M lies inside the circle, and SE otherwise.d =d<0: Select Ednew = d + (2xp+3)d>0: Select SEdnew = d + (2xp–2yp+5)EMSExpxp+1
- 11. MidpointCircle AlgorithmStart with P (x = 0, y = r). Compute d for the first midpoint at (1, r - ½): d = F(1, r - ½) = 5/4 - rWhile (x < y) { If (d <= 0) // E is chosend = d + 2 * x + 3 Else // SE is choseny = y – 1d = d + 2 * x – 2 * y + 5 x = x+1; WritePixel (x, y)}
- 12. Write Points(x,y)Writes pixelsto the seven other octants
- 13. Clipping CirclesAccept/Reject test – Does bounding box of the circle intersect with clipping box?If yes, condition pixel write on clipping box inside/outside testAlso we can test Circle points by Point Clipping .-the point P=(x, y) is display in clipping Boundry if xmin< x <xmaxandymin<y<ymax
- 14. Curve ClippingAreas withcurved boundaries can be clipped with methods similar to those discussedin the previous .sections. Curve-clipping procedures will involve nonlinearequations, however, and this requires more processing than for objects withlinear boundaries.The bounding rectangle for a circle or other curved object can be used firstto test for overlap with a rectangular clip window. If the bounding rectangle forthe object is completely inside the window, we save the object. If the rectangle isdetermined to be completely outside the window, we discard the object. In eithercase, there is no further computation necessary. But if the bounding rectangle testfails, we can look for other computation-saving approaches. For a circle, we canuse the coordinate extents of individual quadrants and then octants for preliminarytesting before calculating curve-window intersections. For an ellipse, we cantest the coordinate extents of individual quadrants. Figure blew illustrates circleclipping against a rectangular window.
- 15. Curve ClippingSimilar procedurescan be applied when clipping a curved object against a general polygon clip region. On the first pass, we can clip the bounding rectangleof the object against the bounding rectangle of the clip region. If the two regions overlap, we will need to solve the simultaneous line-curve equations to obtainthe clipping intersection points.