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61 lines
1.9 KiB
61 lines
1.9 KiB
3 years ago
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%*******************************************************************************
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% function: p_poly_dist
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% Description: distance from pont to polygon whose vertices are specified by the
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% vectors xv and yv
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% Input:
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% x - point's x coordinate
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% y - point's y coordinate
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% xv - vector of polygon vertices x coordinates
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% yv - vector of polygon vertices x coordinates
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% Output:
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% d - distance from point to polygon (defined as a minimal distance from
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% point to any of polygon's ribs, positive if the point is outside the
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% polygon and negative otherwise)
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% Routines: p_poly_dist.m
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% Revision history:
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% 7/9/2006 - case when all projections are outside of polygon ribs
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% 23/5/2004 - created by Michael Yoshpe
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% Remarks:
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%*******************************************************************************
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function d = p_poly_dist1(x, y, xv, yv)
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% If (xv,yv) is not closed, close it.
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xv = xv(:);
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yv = yv(:);
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Nv = length(xv);
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if ((xv(1) ~= xv(Nv)) || (yv(1) ~= yv(Nv)))
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xv = [xv ; xv(1)];
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yv = [yv ; yv(1)];
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Nv = Nv + 1;
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end
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% linear parameters of segments that connect the vertices
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A = -diff(yv);
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B = diff(xv);
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C = yv(2:end).*xv(1:end-1) - xv(2:end).*yv(1:end-1);
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% find the projection of point (x,y) on each rib
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AB = 1./(A.^2 + B.^2);
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vv = (A*x+B*y+C);
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xp = x - (A.*AB).*vv;
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yp = y - (B.*AB).*vv;
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% find all cases where projected point is inside the segment
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idx_x = (((xp>=xv(1:end-1)) & (xp<=xv(2:end))) | ((xp>=xv(2:end)) & (xp<=xv(1:end-1))));
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idx_y = (((yp>=yv(1:end-1)) & (yp<=yv(2:end))) | ((yp>=yv(2:end)) & (yp<=yv(1:end-1))));
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idx = idx_x & idx_y;
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% distance from point (x,y) to the vertices
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dv = sqrt((xv(1:end-1)-x).^2 + (yv(1:end-1)-y).^2);
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if(~any(idx)) % all projections are outside of polygon ribs
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d = min(dv);
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else
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% distance from point (x,y) to the projection on ribs
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dp = sqrt((xp(idx)-x).^2 + (yp(idx)-y).^2);
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d = min(min(dv), min(dp));
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end
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if(inpolygon(x, y, xv, yv))
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d = -d;
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end
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