Is the origin in matedCS in Assembly Definition API a local coordinate or global coordinate?

Answers

• Ethan_K Member, Onshape Employees Posts: 57

  April 2019 edited April 2019 Answer ✓

  Hi @C_Justin,
  
  The first thing to note is that all the responses are in terms of meters, and do use scientific notation where needed, i.e.: -2.312964634635742E-17 is really close to 0 and within the Onshape tolerances of 0.
  
  There are two flavors of mate connector responses within the API response. One is for describing the mate connector of a brought-in part, and the other is for describing a mated assembly mate connector. The one that the part owns (and is defined in the originating PartStudio) both are labeled with the CS relative to the CS of the occurrence. Here is an example response for this API call:
  
  

  {
    "rootAssembly" : {
      "documentId" : "84baa7aab6ea46bdaea38be1",
      "documentMicroversion" : "0b00d3b8050b78c46b499446",
      "elementId" : "0bb88d382ac6e2176378f191",
      "occurrences" : [ {
        "path" : [ "MzbHnGVkP+/LJlZ7s" ],
        "transform" : [ 1.0, 0.0, 0.0, 0.20000000000000007, 0.0, 1.0, 0.0, -1.3877787807814455E-17, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0 ],
        "fixed" : false,
        "hidden" : false
      } ],
      "instances" : [ {
        "id" : "MzbHnGVkP+/LJlZ7s",
        "name" : "Part 1 <1>",
        "partId" : "JHD",
        "isStandardContent" : false,
        "configuration" : "default",
        "type" : "Part",
        "suppressed" : false,
        "documentId" : "84baa7aab6ea46bdaea38be1",
        "documentMicroversion" : "0b00d3b8050b78c46b499446",
        "elementId" : "7eb0a76febc2fdbb7a343a26"
      } ],
      "features" : [ {
        "featureType" : "mateConnector",
        "id" : "MIcB7FY+NyCeX1IvD",
        "suppressed" : false,
        "featureData" : {
          "name" : "Mate connector 1",
          "occurrence" : [ "MzbHnGVkP+/LJlZ7s" ],
          "mateConnectorCS" : {
            "origin" : [ 0.24999999999999994, 0.0, 0.25 ],
            "xAxis" : [ -1.6653345369377348E-16, 1.0, 0.0 ],
            "yAxis" : [ 0.0, 0.0, 1.0 ],
            "zAxis" : [ 1.0, 1.6653345369377348E-16, 0.0 ]
          }
        }
      }, {
        "featureType" : "mate",
        "id" : "Mg6dQzTsYlypZLwXE",
        "suppressed" : false,
        "featureData" : {
          "name" : "Fastened 1",
          "mateType" : "FASTENED",
          "matedEntities" : [ {
            "matedOccurrence" : [ "MzbHnGVkP+/LJlZ7s" ],
            "matedCS" : {
              "origin" : [ -5.088522196198635E-17, 1.3877787807814455E-17, 0.0 ],
              "xAxis" : [ 1.0, 0.0, 0.0 ],
              "yAxis" : [ 0.0, -1.0, 0.0 ],
              "zAxis" : [ 0.0, 0.0, -1.0 ]
            }
          }, {
            "matedOccurrence" : [ ],
            "matedCS" : {
              "origin" : [ 0.2, 0.0, 0.0 ],
              "xAxis" : [ 1.0, 0.0, 0.0 ],
              "yAxis" : [ 0.0, -1.0, 0.0 ],
              "zAxis" : [ -0.0, -0.0, -1.0 ]
            }
          } ]
        }
      } ]
    },
    "subAssemblies" : [ ],
    "parts" : [ {
      "documentId" : "84baa7aab6ea46bdaea38be1",
      "documentMicroversion" : "0b00d3b8050b78c46b499446",
      "elementId" : "7eb0a76febc2fdbb7a343a26",
      "partId" : "JHD",
      "bodyType" : "solid",
      "configuration" : "default",
      "isStandardContent" : false,
      "mateConnectors" : [ {
        "featureId" : "FaCcAun7ujfa74X_1",
        "mateConnectorCS" : {
          "origin" : [ -5.088522196198635E-17, 1.3877787807814455E-17, 0.0 ],
          "xAxis" : [ 1.0, 0.0, 0.0 ],
          "yAxis" : [ 0.0, -1.0, 0.0 ],
          "zAxis" : [ 0.0, 0.0, -1.0 ]
        }
      } ]
    } ],
    "partStudioFeatures" : [ ]
  }

  So the mate connector defined in the PS has a CS relative to the occurrence and is located at parts->mateConnectors->mateConnectorCS
  
  The mate connector defined within the Assembly has a CS relative to the occurrence, and is found at rootAssembly->features->(the first one)->featureData->mateConnectorCS. 
  
  Feel free to poke around the originating document here.
  
  In conclusion, both mateConnectorCS are defined within the CS of the occurrence. 
  

  5
• C_Justin Member Posts: 16 ✭

  May 2019

  Just a quick question for this.
  
  
  I got a mate located here. How can I then get the location of the mate in the world coordinate system?
  
  Also, 
  
  It seems in the occurrence's coordinate system, the mate is not at the origin but the API gives "origin" : [ 2.5117617568793384E-18, 0.0, 0.0 ]", why this is not the case that the mate location is relative to the occurence's coordinate system?

  0
• Ethan_K Member, Onshape Employees Posts: 57

  May 2019

  Hmm, could you share the document? Then we should be able to determine what is happening! And the coordinate you posted is the origin just with a rounding error because floats, you know! (2.5117617568793384E-18 = 0)

  1
• C_Justin Member Posts: 16 ✭

  May 2019

  https://cad.onshape.com/documents/f50dce491bdee895ba806f07/w/dd4826567d4b24e3f5922dfc/e/89fa612e49c9bf6a95ef375d
  This is the document, I think the mate connector connects at someplace near the origin but not the origin(not within  2.5117617568793384E-18)？

  0
• Jake_Rosenfeld Moderator, Onshape Employees, Developers Posts: 1,646

  May 2019

  @C_Justin
  
  Our length tolerance is 10 nanometers (1e-8), anything difference smaller than that we would consider 0.

  Jake Rosenfeld - Modeling Team

  0