Forums Technical Discussion change attribute which is behind the back

change attribute which is behind the back

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luoqiulin
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i need the grid's point feed back different value,when it's front or back from the line by vop!

for example, the line's normal is forward, and if the grid's points is ahead from the line,the grid point's normal is forward too, and if the points is at the back of the line, the point's normal is reversed!

the picture shows my mean, wish you tell me how can i do it in vop！

Attachments:
reverse_back.jpg (176.0 KB)

https://vimeo.com/user3971456/videos [vimeo.com]
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circusmonkey
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How about create 2 lines one for each direction , then create your vector attributes and use attribute transfer onto a point group .

Rob
Gone fishing
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tamte
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lets assume that you are taking that green vector as a direction from nearest point on the line
then you should be able to have access to that point's normal (yellow vector) from any of the green points as well

so just calculate dot product between green and it's corresponding yellow vector and if it is less than 0 just reverse green vector
Tomas Slancik
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Method Studios, NY
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peliosis
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I hope this is what you looked for.
Poindcloud functions are the way to go.

Attachments:
normalsFromCurve.hipnc (95.6 KB)

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luoqiulin
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my first pic is used attributetransfer,
peliosis your hipfile is very helpful for me,but can it feed back two different value like 0–1, to indicate weather it's at the front or back,

so i tried tamte's suggestion , but the result is not accuracy! just like this

Attachments:
bad_pos.jpg (168.9 KB)

https://vimeo.com/user3971456/videos [vimeo.com]
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graham
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You need to dot the normal from the curve with a vector representing the direction from your point on the grid to the closest point on the curve.

Attachments:
curve_normals.hip (71.3 KB)

Graham Thompson, Technical Artist @ Rockstar Games
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luoqiulin
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thank you very much
https://vimeo.com/user3971456/videos [vimeo.com]
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