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<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;">Ok we could do that for imstkSceneObject (allow setting of multiple visual meshes). This would mean that mesh readers could import multiple geometries. Why would we need mesh IDs
though?
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<div id="divRpF320720" style="direction: ltr;"><font face="Tahoma" size="2" color="#000000"><b>From:</b> Sreekanth Arikatla [sreekanth.arikatla@kitware.com]<br>
<b>Sent:</b> Monday, September 25, 2017 12:16 PM<br>
<b>To:</b> Milef, Nicholas Boris<br>
<b>Cc:</b> Alexis Girault; imstk-developers@imstk.org<br>
<b>Subject:</b> Re: [Imstk-developers] Multiple materials per import<br>
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<div dir="ltr">We already support multiple physics materials (thanks to Vega!) within the same mesh in iMSTK. One can define something called regions and assign different material properties for each region. Based on your described, this seems to be not practical
for the case of render materials.
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<div>One solution could be to have the visual geometry be composed of multiple meshes (optionally) while the physics and collision geometries are composed of one mesh-like now. In that case, we need to add mesh IDs in addition to primitive ID in the geometry
mappers.</div>
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<div class="gmail_quote">On Mon, Sep 25, 2017 at 11:56 AM, Milef, Nicholas Boris <span dir="ltr">
<<a href="mailto:milefn@rpi.edu" target="_blank">milefn@rpi.edu</a>></span> wrote:<br>
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<div style="direction:ltr; font-family:Tahoma; color:#000000; font-size:10pt">@Sreekanth, The meshes wouldn't be numbered contiguously in this case. They would just be separate surface meshes. An example would be a car mesh. You would have the tires with one
material, body with another material, windows with another, etc, so they would all belong to a car object but be separate meshes. I think this makes sense as well for when you implement materials for physics (with different friction coefficients, etc.).
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<div style="font-family:Tahoma; font-size:13px">@Alexis, No we shouldn't disassociate the mesh from the material. By applying the material per set of points, you risk having noncontiguous triangles in this case. Also, down the line it makes it difficult to
batch draw objects similar materials.</div>
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<div style="font-family:Tahoma; font-size:13px">Multiple UV channel support (VTK multitexturing) doesn't relate to this problem. In practice, multiple UV coords are only useful for lightmapping or some very specialized use cases. Different meshes belonging
to a larger mesh (object) don't need unique UVs, they just need unique textures.</div>
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<div id="m_-4740301227001859167divRpF358465" style="direction:ltr"><font face="Tahoma" size="2" color="#000000"><b>From:</b> Imstk-developers [<a href="mailto:imstk-developers-bounces@imstk.org" target="_blank">imstk-developers-bounces@<wbr>imstk.org</a>] on
behalf of Sreekanth Arikatla [<a href="mailto:sreekanth.arikatla@kitware.com" target="_blank">sreekanth.arikatla@kitware.<wbr>com</a>]<br>
<b>Sent:</b> Monday, September 25, 2017 11:15 AM<br>
<b>To:</b> Alexis Girault
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<b>Cc:</b> <a href="mailto:imstk-developers@imstk.org" target="_blank">imstk-developers@imstk.org</a><br>
<b>Subject:</b> Re: [Imstk-developers] Multiple materials per import<br>
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<div dir="ltr">We don't support multiple meshes for the same object in doing the physics. However, if two non-connected meshes are numbered contiguously the physics treats it as one but still simulates two bodies. This is generally not done though since there
is not much of a use case. It could happen at runtime when one cuts a mesh into two (eg: pattern cutting simulator).</div>
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<div class="gmail_quote">On Mon, Sep 25, 2017 at 11:01 AM, Alexis Girault <span dir="ltr">
<<a href="mailto:alexis.girault@kitware.com" target="_blank">alexis.girault@kitware.com</a>></span> wrote:<br>
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<div dir="ltr">We wouldn't want to confuse geometries (mesh, etc...) with objects (scene object), which would be part of a scene graph when the needs come.
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<div>Sreekanth: wouldn't creating multiple meshes for a unique object be a problem to handle physics?</div>
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<div>Nick: do we need to dissociate meshes per material? Could we retain a unique mesh and associate materials to a specific set of points/cells? I am remembering of the multi-texture support in VTK, where I had two sets of texture coordinates which allowed
me to combine two textures at different parts of a unique mesh.</div>
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<div dir="ltr"><span style="color:rgb(136,136,136); font-size:12.8000001907349px">Alexis Girault</span><br style="color:rgb(136,136,136); font-size:12.8000001907349px">
<span style="color:rgb(136,136,136); font-size:12.8000001907349px">R&D Engineer in Medical Computing</span><br style="color:rgb(136,136,136); font-size:12.8000001907349px">
<span style="color:rgb(136,136,136); font-size:12.8000001907349px">Kitware, Inc.</span><br style="color:rgb(136,136,136); font-size:12.8000001907349px">
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<a href="http://www.kitware.com/" rel="noreferrer" style="color:rgb(17,85,204); font-size:12.8000001907349px" target="_blank">http://www.kitware.com</a><br style="color:rgb(136,136,136); font-size:12.8000001907349px">
<font color="#999999"><a href="tel:(919)+969-6990+x325" target="_blank"><span style="font-size:12.8000001907349px">(919) 969-6990 x3</span>25</a></font><br>
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<div class="gmail_quote">On Mon, Sep 18, 2017 at 12:09 PM, Andinet Enquobahrie <span dir="ltr">
<<a href="mailto:andinet.enqu@kitware.com" target="_blank">andinet.enqu@kitware.com</a>></span> wrote:<br>
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<div dir="ltr">I would think we will need a scene graph support at some point in iMSTK
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<div>For example, </div>
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<div><a href="https://www.sofa-framework.org/community/doc/main-principles/scene-graph/" target="_blank">https://www.sofa-framework.org<wbr>/community/doc/main-principles<wbr>/scene-graph/</a><br>
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<div class="gmail_quote">On Mon, Sep 18, 2017 at 11:39 AM, Milef, Nicholas Boris <span dir="ltr">
<<a href="mailto:milefn@rpi.edu" target="_blank">milefn@rpi.edu</a>></span> wrote:<br>
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<div style="direction:ltr; font-family:Tahoma; color:#000000; font-size:10pt">Yes, it's very common to have this functionality, and many meshes we have use this. Currently, I have to individually export each material as a separate mesh, but this gets tedious
when you end up with hundreds of meshes and have to separate/export each one individually. Also, managing these is a pain. Note that a single face can only have one material assigned to it (i.e., not layered materials).
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<div>We still don't have the scene graph, but what if we introduce one and then when you import a mesh it adds a new node (called MeshGroup) under root (the scene) and then nodes (meshes) under the MeshGroup? Or it could be called MeshObject or something, etc.
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<font face="Tahoma" size="2" color="#000000"><b>From:</b> Sreekanth Arikatla [<a href="mailto:sreekanth.arikatla@kitware.com" target="_blank">sreekanth.arikatla@kitware.co<wbr>m</a>]<br>
<b>Sent:</b> Monday, September 18, 2017 11:03 AM<br>
<b>To:</b> Milef, Nicholas Boris<br>
<b>Cc:</b> <a href="mailto:imstk-developers@imstk.org" target="_blank">imstk-developers@imstk.org</a><br>
<b>Subject:</b> Re: [Imstk-developers] Multiple materials per import<br>
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<div dir="ltr">Having mesh split and maintained as separate pieces might complicate imstk's geometry mappers. Do you have a use case from one of the projects?</div>
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<div class="gmail_quote">On Mon, Sep 18, 2017 at 10:52 AM, Milef, Nicholas Boris <span dir="ltr">
<<a href="mailto:milefn@rpi.edu" target="_blank">milefn@rpi.edu</a>></span> wrote:<br>
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<div style="direction:ltr; font-family:Tahoma; color:#000000; font-size:10pt">This question has a subtle difference compared to a previous question I asked before, but should we add support for mesh files with multiple materials?
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<div>When the mesh gets imported, the regions with a different material would get split into a new mesh. Or should we introduce a new primitive such as a MeshGroup to handle this? Or should we keep them as separate, unrelated meshes?</div>
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