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92 lines
3.0 KiB
92 lines
3.0 KiB
function [new_n_1,new_n_2,new_Xi_1,new_Xi_2,new_P,new_w] =...
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NURBS_Surface_Refine(d,add_Xi_1,add_Xi_2,p_1,p_2,n_1,n_2,Xi_1,Xi_2,P,w)
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% Determine what new_Xi should look like:
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new_Xi_1 = sort([Xi_1, add_Xi_1]);
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new_Xi_2 = sort([Xi_2, add_Xi_2]);
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% Do all the calculation in projective space: That is multiply the control
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% points by their weights:
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for i = 1:d
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P(:,:,i) = P(:,:,i).*w;
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end
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P(:,:,d+1) = w;
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% Knot Interstion:
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% We know what we want our final knot vector to look like, so we'll do knot
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% insertion until our KV matches our KVF.
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for i = 1:length(new_Xi_1)
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% Check to see if the current knot in KV matches the current knot in
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% KVF. If it does, great, move on to the next knot, if not, calculate
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% new control points and insert KVF(i) into KV(i).
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if new_Xi_1(i) == Xi_1(i)
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continue
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else
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% Correct for the algorithm indexing by zero
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ki = i-1;
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% Calculate the new control points
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% Loop through indexes from k-p+1 to k and calculate the new control
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% points
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for j = ki-p_1+1:ki
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a(j) = (new_Xi_1(i)-Xi_1(j))/(Xi_1(j+p_1)-Xi_1(j));
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Q(j,:,:) = (1-a(j))*P(j-1,:,:) + a(j)*P(j,:,:);
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end
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% Move control points below ki-1 down by 1 space to
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% make room for the p new points;
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P(ki+1:size(P,1)+1,:,:) = P(ki:size(P,1),:,:);
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% Insert the new control points
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P(ki-p_1+1:ki,:,:) = Q(ki-p_1+1:ki,:,:);
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% move the knots to the right of the knot to be inserted over one
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% index
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Xi_1(i+1:end+1) = Xi_1(i:end);
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% Insert the knot to the knot vector.
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Xi_1(i) = new_Xi_1(i);
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end
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end
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for i = 1:length(new_Xi_2)
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% Check to see if the current knot in KV matches the current knot in
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% KVF. If it does, great, move on to the next knot, if not, calculate
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% new control points and insert KVF(i) into KV(i).
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if new_Xi_2(i) == Xi_2(i)
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continue
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else
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% Correct for the algorithm indexing by zero
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ki = i-1;
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% Calculate the new control points
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% Loop through indexes from k-p+1 to k and calculate the new control
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% points
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for j = ki-p_2+1:ki
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a_2(j) = (new_Xi_2(i)-Xi_2(j))/(Xi_2(j+p_2)-Xi_2(j));
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Q_2(:,j,:) = (1-a_2(j))*P(:,j-1,:) + a_2(j)*P(:,j,:);
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end
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% Move control points below ki-1 down by 1 space to
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% make room for the p new points;
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P(:,ki+1:size(P,2)+1,:) = P(:,ki:size(P,2),:);
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% Insert the new control points
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P(:,ki-p_2+1:ki,:) = Q_2(:,ki-p_2+1:ki,:);
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% move the knots to the right of the knot to be inserted over one
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% index
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Xi_2(i+1:end+1) = Xi_2(i:end);
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% Insert the knot to the knot vector.
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Xi_2(i) = new_Xi_2(i);
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end
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end
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new_w = P(:,:,d+1);
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for i = 1:d
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new_P(:,:,i) = P(:,:,i)./new_w;
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end
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new_n_1 = size(new_P,1);
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new_n_2 = size(new_P,2);
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return
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