<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi,<div> I am trying to understand what goes on behind the scenes and what to take care of, when importing data into VTK, displaying objects and measuring them using a distance widget. </div><div><br></div><div>I just need a second opinion to confirm that I am on the right track. I've done computer graphics as a subject in engineering, plus read the Computer Graphics Book by Van Damme and Foley, so I've read the theory ages ago, but I just need to check if I'm on the right track with what I'm assuming is happening in VTK. </div><div><br></div><div>This is because distance measurement and measurement accuracy is very important in the application prototype that I am trying to construct.</div><div><br></div><div>Suppose I model a triangle as follows:</div><div><br></div><div><div><font class="Apple-style-span" face="Monaco" size="2"><span class="Apple-style-span" style="font-size: 10px;">vtkPoints trianglePoints</span></font></div><div><font class="Apple-style-span" face="Monaco" size="2"><span class="Apple-style-span" style="font-size: 10px;"> trianglePoints SetNumberOfPoints 3</span></font></div><div><font class="Apple-style-span" face="Monaco" size="2"><span class="Apple-style-span" style="font-size: 10px;"> trianglePoints InsertPoint 0 0 0 0</span></font></div><div><font class="Apple-style-span" face="Monaco" size="2"><span class="Apple-style-span" style="font-size: 10px;"> trianglePoints InsertPoint 1 1 0 0</span></font></div><div><font class="Apple-style-span" face="Monaco" size="2"><span class="Apple-style-span" style="font-size: 10px;"> trianglePoints InsertPoint 2 .5 .5 0</span></font></div><div><br></div><div>This would imply that the x axis distance between point 0 and point 1 will be 1 unit.</div><div><br></div><div><b>Question 1: I</b>f I add this triangle actor to a renderer and render the scene, straight away, am I correct in saying that if no model to world transformations were applied, the triangle will retain all its original physical dimensions? When I attempted to use the vtkDistanceWidget to measure the distance between point 0 and point 1, it approximately showed 1.0.</div><div><br></div><div><img height="448" width="504" apple-width="yes" apple-height="yes" src="cid:E1D169D6-789A-4C96-8494-3A59F9CB0778@du.ae"></div><div><b>Question 2:</b> If I were to scale the triangle to half it's original size, at which point should I apply the model to world coordinate transformation? </div><div><br></div><div>In the above example, the triangle is represented as an unstructured grid. </div><div><br></div><div>Should I first pass it to a data set mapper, generate the polygonal data and then apply, say a scaling transformation, so that the distance between point 0 and point 1 is reduce to 0.5?</div><div><br></div><div>Best regards,</div><div><br></div><div>Elvis Dowson </div></div></body></html>