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Hexagon crashing when selecting faces
Posted: 08 June 2012 08:34 PM   [ Ignore ]   [ # 31 ]
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Design Acrobat - 08 June 2012 07:41 PM

sknaht yrev hcum rof eht deliated noitanalpxe!

 
¡ǝɯoɔןǝʍ ǝʇınb ǝɹ,noʎ

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For any arguments or illustrations I give, my system specs are:
Hexagon version 2.5.1.79,  XP pro 32 bit,  pentium core2 duo,  ATI radeon 3870, 2 gigs ram

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Posted: 08 June 2012 11:08 PM   [ Ignore ]   [ # 32 ]
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afreaginname - 08 June 2012 01:15 PM

Turns out that when you draw a quad CCW and then draw a CW quad next to it in the workspace, hexagon instantly rewinds the CW quad so that both normals are facing you. Hexagon obviously assumes that if a user creates a quad, he’s creating the face he wants to see. This isn’t a bug, it’s actually perfectly reasonable and in this case, hexagon does its job at the expense of making me look like an idiot.  LOL

Actually Hex does several strange things when it comes to normals and winding order.

Create a plane/grid. duplicate it and move one forward. try bridging 2 adjacent edges and Hex flips one of the planes. Flip one of the planes back and it should look like below.

For something this simple it’s not an issue. However it could make a mess of a complicated mesh especially if it happens a few times during the modeling. I would call that a bug long before calling it perfectly reasonable. I’m assuming Hex just flipped one of the planes also and didn’t create a double edge witch would be even worse.

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Posted: 09 June 2012 02:11 AM   [ Ignore ]   [ # 33 ]
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admkrk - 08 June 2012 11:08 PM

Create a plane/grid. duplicate it and move one forward. try bridging 2 adjacent edges and Hex flips one of the planes. Flip one of the planes back and it should look like below

 
I may be missing something here, but I can’t seem to duplicate your image.
 
I created a quad such as the one on the left, and copied it to a position such as the one on the right. Both normals at this point are facing to the right.
 
Then I bridged the rearmost edges (the edges bounding your triple-tri), and it bridged cleanly with a simple plane, but yes - the normal of the quad on the right got flipped inwards. At this point, I had 3 sides of a box with all the normals facing inward, as though hexagon unified the normals of all 3 elements involved in the bridge.
 
I then reversed the normal of the quad on the right with no problem. I now had the left and right quads both facing to the right again, and the bridged quad facing me.
 
I also tried dragging the quad on the right back and forth so that it passed through the left quad. When it was to the right of the left quad, the bridged poly’s normal was facing me. When I moved it to the left of the left quad, the bridged poly flipped its normal so that it was facing away from me - which is not unexpected.
 
So I’m still at a loss as to how you got that triple-tri in your image.

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For any arguments or illustrations I give, my system specs are:
Hexagon version 2.5.1.79,  XP pro 32 bit,  pentium core2 duo,  ATI radeon 3870, 2 gigs ram

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Posted: 09 June 2012 02:44 PM   [ Ignore ]   [ # 34 ]
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Hex won’t create that because it flips one of the planes on it’s own.

What you’re referring to as as triple tris is a twisted quad like n-gon in the original post. The blue lines are border edges, I have no idea why there is anything in the middle it should look like a bow tie. Because in this instance the normals/winding order wasn’t changed the top point on the front plane bridged to the bottom point on the rear plane and vise versa. If I had tried to create a polygon between the two edges instead of bridge I would get a warning with the option to flip one of the planes. Hex just does that on it’s own without letting you know. It might seem convenient on something like this but when dealing with a larger project of several thousand polys and having this happen several times it could very well cause problems like the twisted n-gon that crashes Hex.

Hex doing this on it’s own is probably also why it does funky things with booleans. 

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Posted: 10 June 2012 05:25 AM   [ Ignore ]   [ # 35 ]
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afreaginname - 08 June 2012 01:15 PM

Turns out that when you draw a quad CCW and then draw a CW quad next to it in the workspace, hexagon instantly rewinds the CW quad so that both normals are facing you. Hexagon obviously assumes that if a user creates a quad, he’s creating the face he wants to see. This isn’t a bug, it’s actually perfectly reasonable and in this case, hexagon does its job at the expense of making me look like an idiot.  LOL

It depends on what tools you are using.

If you are constructing a quad/polygon using the “3d primitives-> facet” then Hexagon will automatically flip the polygon normal to face camera. However:-
If you draw a square (using poly-line tool), one clockwise (drawing 3 lines, then selecting close, to create the square), then one anti-clockwise, you will see the possible problems when using other tools on those lines, such as:-
Extrude each of those squares in the same direction, the normals on the (from each square) extruded polygons will be in different directions, or, use “Surface modeling-> coons surface” on each square(of lines) and those will also be in different directions.

 

 

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