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Face Offset & Face Vertex from Get Mesh structure

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Message 1 of 11
moiamy
769 Views, 10 Replies

Face Offset & Face Vertex from Get Mesh structure

In the excellent demo of "Bifrost Visual Programming Masterclass - Part 1 of 2", I dont get why he doesn't take the (face offset) & (face vertex) output from the (get mesh structure) to plug directly inside the new (construct mesh)as the structure is identical ?

 

 

construct mesh.jpg

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10 REPLIES 10
Message 2 of 11
g2m.agent
in reply to: moiamy

Because he needs to separate each face, similar to reverse "merge vertices".

Message 3 of 11
mjcg91
in reply to: moiamy

@moiamy You are correct, The new face offset is identical to the previous one. There is no need to re-generate the face_offset in this case. Only the face_vertex has to be re-generated according to the new point positions.

Maxime Jeanmougin - Technical Artist
https://maximejeanmougin.com

Join the Bifrost Addicts community on Discord:
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Message 4 of 11
moiamy
in reply to: mjcg91

Indeed @mjcg91 face_vertex needs to go through a new sequence_array

Still a bit confusing for me

I guess when I will find a way to check in detail data inside output array I will understand better...

Message 5 of 11
moiamy
in reply to: moiamy

Pushing further my undertsandings about this part, I would like to understand the [Access Offset Array] Compound.

 

So here is a basic drawing I made

 

 

01 for each.jpg

 

If we enter inside [For each] compound, there is the [access offset array]

 

Is this computation correct ?

 

If  [Input] current_index ==0

           [Access Offset Array] start = [input] face_offset [0]

            [Access Offset Array] end = [input] face_offset [1]

 

 

02 for each inside.jpg

 

 

03 access offset array.jpg

Message 6 of 11
mjcg91
in reply to: moiamy

Yes that's correct. The face_offset defines the range of face_vertex per face. Basically it defines how many face vertex are used by a face (length), and where in the face_vertex array the first face vertex of this face is (start). With these data you can use it to slice the face_vertex array and get all the face vertex indices of a specific face.

Maxime Jeanmougin - Technical Artist
https://maximejeanmougin.com

Join the Bifrost Addicts community on Discord:
https://discord.gg/bifrost-addicts
Message 7 of 11
moiamy
in reply to: mjcg91

Actually there is a substract operation in the [access_offset_array] compound.

So shouldn't it be

 

If [Input] current_index ==0
    [Access Offset Array] start = [input] face_offset [0]
    [Access Offset Array] end = [input] face_offset [1] - 1 

 

 

Message 8 of 11
mjcg91
in reply to: moiamy

I wouldn't worry about how the access_offset_array works. It just gives you what you need to access per face / per strands data in Bifrost. Most of the time you only need start and length. end is usually used along with the slice node.

If this can help, I made this offset visualization for my Bifrost Strands blog post. The face offset works the same except it defines the face_vertex elements for each faces.

 

strands_offset_visualized.gif

Even though its post about strands, you can learn more about offset arrays here.
https://maximejeanmougin.com/2020/09/08/bifrost-strands/

Maxime Jeanmougin - Technical Artist
https://maximejeanmougin.com

Join the Bifrost Addicts community on Discord:
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Message 9 of 11
moiamy
in reply to: mjcg91

@mjcg91 

Did you use Manim for the animation ?

Message 10 of 11
mjcg91
in reply to: moiamy

I made it with Bifrost 😅

Maxime Jeanmougin - Technical Artist
https://maximejeanmougin.com

Join the Bifrost Addicts community on Discord:
https://discord.gg/bifrost-addicts
Message 11 of 11
moiamy
in reply to: mjcg91

Write a book Maxime... it will be sold out in one week !

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