<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div id="yui_3_16_0_1_1426706167683_23951">But voxels of a CT (MRI) image cannot be considered infinitesimal thin, can they?</div><div id="yui_3_16_0_1_1426706167683_23995"><br></div><div id="yui_3_16_0_1_1426706167683_23891" dir="ltr">Maarten<br></div><div id="yui_3_16_0_1_1426706167683_23865"><span></span></div> <br><div class="qtdSeparateBR"><br><br></div><div style="display: block;" class="yahoo_quoted"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div dir="ltr"> <font size="2" face="Arial"> On Wednesday, March 18, 2015 3:16 PM, David Gobbi <david.gobbi@gmail.com> wrote:<br> </font> </div> <br><br> <div class="y_msg_container"><div id="yiv5835417802"><div><div dir="ltr">You can define "outside" to be whatever you want, but VTK defines "outside the bounds" to mean "beyond the data points that form the edge of the data set." :)<div><br clear="none"></div><div>If, for example, I wanted to intersect a line with the first and last slice of the volume, I would _not_ add 0.5*spacing. But that's because I consider my "slice" to be an infinitesimally thin object. So according to my definition of "slice", the distance between one end of the volume and the other is 99 times the spacing.</div><div><br clear="none"></div><div>Really, how you define things will depend partly on the requirements of your application. I'm just saying what my own definitions are.</div><div><br clear="none"></div><div> - David</div><div><div><br clear="none"></div></div></div><div class="yiv5835417802yqt6430014793" id="yiv5835417802yqt95258"><div class="yiv5835417802gmail_extra"><br clear="none"><div class="yiv5835417802gmail_quote">On Wed, Mar 18, 2015 at 12:58 PM, Maarten Beek <span dir="ltr"><<a rel="nofollow" shape="rect" ymailto="mailto:beekmaarten@yahoo.com" target="_blank" href="mailto:beekmaarten@yahoo.com">beekmaarten@yahoo.com</a>></span> wrote:<br clear="none"><blockquote class="yiv5835417802gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"><div>Hi David,</div><div><br clear="none"></div><div dir="ltr">To clarify.</div><div dir="ltr">Since "the bounds of avolume start and end in the center of the corner voxels.", I would have to expand the bbox in all directions by 0.5*spacing to get the intersections with the 'outside' planes of the image? And the distance between one 'outside' and its opposite 'outside' would be 100 times the spacing?<span class="yiv5835417802HOEnZb"><font color="#888888"><br clear="none"></font></span></div><span class="yiv5835417802HOEnZb"><font color="#888888"></font></span><div dir="ltr"><br clear="none"></div><div dir="ltr">Maarten<br clear="none"></div><div><div class="yiv5835417802h5"><div><span></span></div> <br clear="none"><div><br clear="none"><br clear="none"></div><div style="display:block;"> <div style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"> <div style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"> <div dir="ltr"> <font face="Arial"> On Wednesday, March 18, 2015 9:42 AM, David Gobbi <<a rel="nofollow" shape="rect" ymailto="mailto:david.gobbi@gmail.com" target="_blank" href="mailto:david.gobbi@gmail.com">david.gobbi@gmail.com</a>> wrote:<br clear="none"> </font> </div> <br clear="none"><br clear="none"> <div><div><div><div dir="ltr">Hi Maarten,<div><br clear="none"></div><div>If you used (0, 13, ...) then you'd get the wrong answer. The bounds of a</div><div>volume start and end in the center of the corner voxels. If the first voxel</div><div>is 0 and the last voxel is 99, then the real-world dimension of the volume is</div><div>99 times the spacing.</div><div><br clear="none"></div><div>A voxel is a data point. Emphasis on "point". If you have a series of data</div><div>points, anything before the first point or after the last point is outside of the</div><div>bounds of the data points.</div><div><br clear="none"></div><div> - David </div><div><br clear="none"></div><div><div><div><br clear="none"><div>On Wed, Mar 18, 2015 at 7:23 AM, Maarten Beek via vtkusers <span dir="ltr"><<a rel="nofollow" shape="rect" ymailto="mailto:vtkusers@vtk.org" target="_blank" href="mailto:vtkusers@vtk.org">vtkusers@vtk.org</a>></span> wrote:<br clear="none"><blockquote style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"><div dir="ltr">Hi all,</div><div dir="ltr"><br clear="none"></div><div dir="ltr">For an image with dims = (100, 100, 100) and spacing = (0.13, 0.13, 0.13), vtkImageData::GetBounds() returns</div><div dir="ltr">(0, 12.87, 0, 12.87, 0, 12.87)</div><div dir="ltr"><br clear="none"></div><div dir="ltr">If I use these bounds as argument in vtkBox::IntersectWithLine, do I get the correct intersections?</div><div dir="ltr">Or should I use (0, 13, 0, 13, 0, 13) for the bounds?</div><div dir="ltr"><br clear="none"></div><div dir="ltr">Thanks - Maarten<br clear="none"></div></div></div><br clear="none">
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