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Off on a tangent... Part 1
March 21, 2008, 08:02 PM Jay TedeschiI want you to think for a moment of the obstacles that need to be overcome when creating conformal objects of any type for consumer electronic products. In the case presented here we have buttons on a game controller that must match the contours of the controller housing, however must also be raised slightly above the housing surface for easy actuation.
To achieve this we will use an offset surface from the controller housing itself, however there is a problem with this approach as the resultant surface has holes which match those areas in the housing surface where the button cutouts and blends are.
We need to patch these holes, but need these new surfaces to have the same curvature as the housing itself. So, how do we get a clean, contoured surface, which can be used to give us the conformal cut we are looking for, and that will be associative to any modifications to the housing itself? The boundary patch will give us the results we need, but we will have to set the proper conditions to get the desired results. Take a look at the image below.
The only input that is needed from the user is to select an edge boundary which defines a closed area. As you can see, the edge need not be planar, and in this example I have selected the most extreme hole to patch from a standpoint of curvature. Once selected, if I rotate the model you will see that in the default “Free Condition” the contour of the boundary patch does not match that of offset surface. This is due to the fact that the continuity of the patch in the “Free Condition” is G0, which quite simply means the the curves or in this case surfaces touch at the join point. Obviously, as you can see from the image, this is “slightly less” [grin] than what we probably had in mind when we were thinking of conformity.
“Tangent Condition” will give us a boundary patch with a continuity of G1, which is as the name implies is tangent, or more specifically will result in a set of curves or surfaces which both touch and share a common tangent direction at the join points. As you can see above, changing to a “Tangent Condition” gives us a much better result, and most likely more in line with what we were looking for in the first place.
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