<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Dear Howard,<div class=""><br class=""></div><div class="">I opened your STL with Blender (<a href="https://www.blender.org" class="">https://www.blender.org</a>) and I can see one problem with your STL:</div><div class=""><ul class="MailOutline"><li class="">the normals are not all facing outwards, see attached screenshot.</li></ul></div><div class=""><br class=""></div><div class="">This means that GATE (Geant4) will not be able to create a closed volume from the STL, </div><div class="">and therefore this ‘phantom’ will be transparent to X-rays.</div><div class=""><br class=""></div><div class="">One easy solution is to ask Blender to recalculate the normals outside (Menu Mesh -> Normals -> Recalculate Outside) and then save (File -> export to STL, beware of the coordinates).</div><div class=""><br class=""></div><div class="">The best is to revise the way you produce your STL so it is correct from the start. And then Blender is just an easy way to check the STL files you create.</div><div class=""><br class=""></div><div class="">I believe it will now work in GATE.</div><div class=""><br class=""></div><div class="">Good luck,</div><div class=""> Maxime Chauvin</div><div class=""><br class=""></div><div class=""><img apple-inline="yes" id="C5D21A89-714F-4A47-B7F6-5FD14092E625" src="cid:1028225B-E9D0-4662-82EC-FD871D7BEC84@inserm.lan" class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On 7 Jul 2020, at 05:35, Howard <<a href="mailto:lomahu@gmail.com" class="">lomahu@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class="">Dear Gate-users,</div><div class=""><br class=""></div><div class="">Is there anyone out there an expert on the tessellated volume? I generated a tessellated mesh object based on a 3x3 binary matrix:</div><div class=""><br class=""></div><div class="">0 1 0</div><div class="">1 1 1</div><div class="">0 1 0</div><div class=""><br class=""></div><div class="">where 0 means completely opaque and 1 completely transparent. For some reason when I applied this volume in GATE as a phantom (set materials as Tungsten) for X-ray, there was no beam attenuation. In other words, this volume behaved like an empty shell instead of a solid piece. The STL file for this volume in ASCII format is attached to this email for your reference.</div><div class=""><br class=""></div><div class="">It would be truly appreciated if any expert on tessellated volume can help out or suggest any software allowing us to look for more detail of the volume? <br class=""></div><div class=""><br class=""></div><div class="">Howard<br class=""></div></div>
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