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--- visual3d:getting_started:visual3d_faq [2025/05/29 14:26] – wikisysop
+++ visual3d:getting_started:visual3d_faq [2025/05/29 14:36] (current) – [Visual3D FAQ] wikisysop
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 ====== Visual3D FAQ ======
-This Frequently Asked Questions page contains a fairly eclectic mix of questions regarding Visual3D. It is made up of questions that are regularly asked by users via support@has-motion.ca and the typical answers provided by us to those questions. More complete solutions/answers/explanations can be found within the HAS-Motion documentation wiki. Wherever appropriate, links to information within the wiki are provided. "Subject-specific" FAQ pages, dealing with individual topics, can be found by using the FAQ Category link at the bottom of this page and some questions here are also on those other pages.
+This Frequently Asked Questions page contains a fairly eclectic mix of questions regarding Visual3D. It is made up of questions that are regularly asked by users via support@has-motion.ca and the typical answers provided by us to those questions. More complete solutions/answers/explanations can be found within the HAS-Motion documentation wiki. Wherever appropriate, links to information within the wiki are provided. Modeling FAQs can be found [[visual3d:documentation:modeling:modeling_faq|here]].
 ===== FAQs =====
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 **Question**: When I look at **“Data Values”** in a FORCE signal, within the Signals and Events tree, what are the **X SUB, Y SUB and Z SUB** values?
-Many people collect analog data at a higher rate than their motion capture data, which is the point rate.
+Many people collect analog data at a higher rate than their motion capture data, which is the point rate. This is fine, as long as the higher rate is an integer multiple of the point rate. When force data are applied to a model, the resulting Link_Model_Based data are at point rate. This is because forces applied to segments cannot be calculated where the segment location is unknown (between point frames), i.e. there are no target data to generate segment locations for the ‘extra’ analog frames. However, the FORCE data retain the analog data rate. These ‘extra’ sample points are displayed as SUB frames within the point rate. The first subframe is synchronized with the point data, and it is this first subframe that is used for Inverse Dynamics calculations. Other Link_Model_Based data, which are based on segments, are also sampled at the point rate, since segmental data can only ever be calculated at point rate.
-This is fine, as long as the higher rate is an integer multiple of the point rate.
-When force data are applied to a model, the resulting Link_Model_Based data are at point rate.
-This is because forces applied to segments cannot be calculated where the segment location is unknown (between point frames),
-i.e. there are no target data to generate segment locations for the ‘extra’ analog frames.
-However, the FORCE data retain the analog data rate.
-These ‘extra’ sample points are displayed as SUB frames within the point rate.
-The first subframe is synchronized with the point data, and it is this first subframe that is used for Inverse Dynamics calculations.
-Other Link_Model_Based data, which are based on segments, are also sampled at the point rate, since segmental data can only ever be calculated at point rate.
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 **Question**: What does **CalTester** do?
-The COFP signal is created by transferring the centre of pressure calculated inside the force platform’s coordinate system into the global, laboratory coordinate system. This transfer is based on the location of the force platform’s corners and the offset between the top of the force sensors and the top of the platform’s surface. The correct position of the COFP is key to accurate inverse dynamic calculations. Put simply, CalTester allows you to compare the position of the COFP, which has been transformed from the force platform’s coordinate system into the global, laboratory coordinate system with how that position is represented using motion capture data. We can do this because we know where the end of the calibrated CalTester rod is in space, and can compare this to the calculated position of the COFP. The two can then be ‘calibrated’ to bring them closer together by altering the force platform location parameters. In order to ensure best results it is important to follow a few simple steps. Always Begin the data capture with the CalTester rod not in contact with the force platform, but make sure the base plate is in situ. This allows Visual3D to calculate a baseline zero for all the force platform channels. Once the rod is in contact with the base plate, the CalTester should be the only thing that comes in contact with the force platform. Ensure the rod is loaded longitudinally with a load of at least 200 N and that, during the data collection, the angle of the rod is no more than about 20 degrees. This will maximise accuracy of COFP calculation from the kinetic data and prevent the CalTester rod’s tip sliding away from the bottom of the dimple in the base plate and being elevated.
+The COFP signal is created by transferring the center of pressure calculated inside the force platform’s coordinate system into the global, laboratory coordinate system. This transfer is based on the location of the force platform’s corners and the offset between the top of the force sensors and the top of the platform’s surface. The correct position of the COFP is key to accurate inverse dynamic calculations. Put simply, CalTester allows you to compare the position of the COFP, which has been transformed from the force platform’s coordinate system into the global, laboratory coordinate system with how that position is represented using motion capture data. We can do this because we know where the end of the calibrated CalTester rod is in space, and can compare this to the calculated position of the COFP. The two can then be ‘calibrated’ to bring them closer together by altering the force platform location parameters. In order to ensure best results it is important to follow a few simple steps. Always begin the data capture with the CalTester rod not in contact with the force platform, but make sure the base plate is in situ. This allows Visual3D to calculate a baseline zero for all the force platform channels. Once the rod is in contact with the base plate, the CalTester should be the only thing that comes in contact with the force platform. Ensure the rod is loaded longitudinally with a load of at least 200 N and that, during the data collection, the angle of the rod is no more than about 20 degrees. This will maximize accuracy of COFP calculation from the kinetic data and prevent the CalTester rod’s tip sliding away from the bottom of the dimple in the base plate and being elevated.
-See [[https://www.c-motion.com/v3dwiki/index.php/CalTester|CalTester documentation]]
+See [[caltester:caltester_mode_overview|CalTester documentation]]
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-We recommend that gap filling is done in Visual3D. There are two reasons why we think so. Firstly, Visual3D always retains the raw (unfilled) target data in the TARGET::ORIGINAL folder. This allows you to easily re-process the original data without having to re-label from scratch. It is possible to re-process original data within motion capture software, such as Nexus or QTM for instance, but this requires a complete re-label, which can be time consuming and laborious (as we all know!). The second reason we think gap filling should be done within Visual3D is becauseVisual3D maintains an audit trial of how the TARGET data are processed. This includes any gap filling. Thus, years later you can simply open the CMO file and look at the processing history of your target data and determine whether gap filling was used, and if it was, what parameters were used to fill the gaps. If you gap fill in your motion analysis software, as time goes by you may not recall how the gaps were filled (we certainly wouldn’t!). If you are more comfortable filling any gaps in your motion analysis software that is fine, however we strongly recommend making a record of what was filled, and how it was filled for later reference.
+We recommend that gap filling is done in Visual3D. There are two reasons why we think so. Firstly, Visual3D always retains the raw (unfilled) target data in the TARGET::ORIGINAL folder. This allows you to easily re-process the original data without having to re-label from scratch. It is possible to re-process original data within motion capture software, such as Nexus or QTM for instance, but this requires a complete re-label, which can be time consuming and laborious (as we all know!). The second reason we think gap filling should be done within Visual3D is because Visual3D maintains an audit trial of how the TARGET data are processed. This includes any gap filling. Thus, years later you can simply open the CMO file and look at the processing history of your target data and determine whether gap filling was used, and if it was, what parameters were used to fill the gaps. If you gap fill in your motion analysis software, as time goes by you may not recall how the gaps were filled (we certainly wouldn’t!). If you are more comfortable filling any gaps in your motion analysis software that is fine, however we strongly recommend making a record of what was filled, and how it was filled for later reference.
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