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I'm trying to understand what happens when the isovalue is the same as the data value when using a marching "squares" algorithm. So for example, if you have the following 2D grid:

enter image description here

Now if you take an isovalue of 5 and draw the lines when it encounters blocks like these?

5----10  10----0  0----10
|     |  |     |  |     |
|     |  |     |  |     |
0-----0, 5----10, 0-----5

I've attempted drawing it here, but I'm not sure it's correct:

enter image description here

Mosbas
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  • Although it technically does not make much difference, I find it more intuitive to imagine the values to be stored at the grid points (and not in the "center of the cell"). The result is (just one of the first websearch results: ) http://media2mult.uos.de/pmwiki/fields/cg-II-09/m2m.d/GrundlagenDerVisualisierung.MarchingSquares/media/image/contouring.png - In this case, when the isovalue is located at a grid point, the lines will pass through it. (I didn't entirely understand what your question is and what the image suggests, sorry) – Marco13 Mar 21 '16 at 23:47
  • @Marcos13 What you're saying doesn't really make any sense. The image is not really that helpful either without knowing what the isovalue is. My question is simply, what do you do when the isovalue is the same as the datavalue, so in this case the isovalue is 5, and the data value of one of the cells is 5, so where is the line drawn? – Mosbas Mar 22 '16 at 00:06
  • The isovalue in the linked image is about 5. However, when the isovalue is 5 and the value of a cell (corner) is 5, then the line goes through the corner. – Marco13 Mar 22 '16 at 00:09
  • So is what I've drawn correct or should it be drawn differently? – Mosbas Mar 22 '16 at 00:12
  • Assuming that the values are located at the centers of the grid cells, I would say that the drawing is correct. – Marco13 Mar 22 '16 at 11:29

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