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Hash, Inc. - Animation:Master

The Mystery of the Four-Sided Non-Patch


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  • Hash Fellow

I was resplining an "A" that didn't come out of the FontWizard quite right and have created what should be a legal four-sided patch... four CPs, connected by splines and not all on the same spline... and yet it doesn't fill in.

 

If I copy just those four CPs and paste them to the right they do fill in but not if they are part of the whole mesh.

 

Anyone know what is wrong?

 

(This is not a Hide Backfaces problem)

 

Fixin A.mdl

 

 

PatchMystery.JPG

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The first thing I noticed is that spline continuity took several of the spline paths in odd directions... going down the side and then following the bottom/back half of another spline down to the base of the letter.

In attempting to correct that continuity it appears to me that there were several duplicate splines, although I couldn't see them. When deleting a terminal point (CP) at what was registering as the end of a spline what remained after the delete was another spline whereas deleting it should have simply removed that section of the spline.

 

It appears to me that A:M is getting confused between terminal endings and continuous splines.

This might be due to a number of things to include that the model was created using v19.

So what we see here in v18 might not be what you are seeing.

 

Diving in and recreating the splines to get continuity sorted out resolved the issue on my end but I'm not sure what the initial problem is/was.

 

 

Added: As to why the patch renders after a copy/paste I'd say A:M is fixing the continuity or simply removing unnecessary splines in that process because A:M is always trying to resolve legit splines into patches.

Fixin A splines rerouted.mdl

Fixin A.jpg

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The Faber Sans font wasn't installed on my computer so I downloaded and installed one from the internet for further testing.

Unfortunately, this Faber Sans isn't the same as the one you used.

It did work quite well though in the Font Wizard.

 

So, I chased another rabbit there as this appears to be another font called Faber Sans reduced.

 

 

 

 

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Hello, It is because that all the sides of the patche are in the same spline. It is not possible to make a patche with a single spline.
By copying, you dont' take all the spline , you select four segment of the splines, so you break the spline in 4 splines which is why it becomes visible.
PS: it is the same problem as this report: http: //www.hash.com/reports/view.php id = 5593
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What is odd about this topology is that selecting a spline around that opening in question (with the comma key) results in several spline sections from different sides of the model all being selected even though they do not appear to be connected in any way. So something is wrong in the splines themselves and we aren't getting a legit setup for a patch at that location.

 

This discontinuity tells me that A:M thinks there is another spline that is connecting these segments.

So there either is another spline or A:M just thinks there is.

 

 

Malo,

While generally correct the following isn't quite a true statement:

It is not possible to make a patche with a single spline.

 

If this read 'it is not possible to create a four-sided patch with a single spline' I'd be inclined to agree.

We know that a 5 point patch can be made from a single spline.

As you are the one that enlightened me on the possibilities for 5 point patches on a single spline I must assume you meant four point patches on a single spline.

Note that all CPs in green have been selected via the use of comma key which suggests they are continuous although visually they are not.

 

Robert,

Attached is an indicator of why these splines don't constitute a legitimate patch at that location.

From what I can tell the indication is that a hidden spline is running below the topmost spline connecting to the CP on the right.

Extra Splines.jpg

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you're right, Rodney, "it is not possible to create a four-sided patch with a single spline" is better! :)

the peculiarity of the spline selection by the keyboard "," that if the spline crosses an even number of times an intersection. then CPs will not be selected. If it is an odd number then they will be selected.(apart if the CP is the referent of the selection.) (this could be considered a bug?)

234.jpg

It is why you seem to have more than one spline selected (in reality, it is the same spline, but some CPs are lost.)
A.jpg

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