# Creating a regular mesh

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Can anyone show me how to create a regular mesh to fit into a particular geometry? Currently I have the geometry of the following structure in the 3d world: As you can see above, the mesh is irregular and manipulation would be difficult. I would like to create a regular mesh to fit the above geometry so that it will be easier to manipulate.

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It looks like that your mesh is "flat" enough such that it can be represented as a height map. If this is true, the conversion should not be too difficult.

Say, the x- and y-axis in 3D space corresponds to the window x- and y-axis of your screenshot (otherwise, rotate the 3D geometry accordingly).

1) Project all nodes p_n of the irregular mesh to the x-y-plane by simply leaving out the z-coordinate ("push the book flat"). You get 2D-points q_n.

2) Find the outer perimeter of the 2D-points q_n. That's the outer boundary of the book in your screenie.

3) Find a regular mesh with nodes g_n for the 2D region that is contained in the border found in 2). To do this, just put a rectangular grid on top of the border and correct the outmost nodes to coincide with the boundary.

4) Find the z-coordinate of the regular grid from 3) by projecting the 2D grid points g_n back to the book. This requires computing intersections of lines (g_n+t*(0,0,1)) and triangles (of the irregular mesh), but should be no problem. Note: If the book is really a heightmap, you'll always get exactly one intersection.

hth

Lutz

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Thanks for the reply. Is there any link which elaborate more on of your above method. I am pretty new to this so will need more details in order to implement it.

Btw, the structure is not really exactly flat. Here is a cross-sectional view of it.

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It looks like you're trying to make pages in a book. Could try for a cloth simulation; that way it would behave like actual paper.

Did you compute the triangulation on the fly? It looks great!

Cheers,
- llvllatrix

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I thought I remembered those pictures. You also started a thread three and a half months ago on a related, but not identical topic. I'll just post a link here since some of the things mentioned in the other thread may help people better understand what you're trying to do or what you've tried. Linky.

Enigma

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Wouln't it be easier to make a new mesh rather that trying to fix the old one.
if you want a procedural one you could try using a nurb mesh,it would work just fine for this.

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Quote:
 Original post by llvllatrixIt looks like you're trying to make pages in a book. Could try for a cloth simulation; that way it would behave like actual paper.Did you compute the triangulation on the fly? It looks great!Cheers,- llvllatrix

No, it was not made on the fly. The information was obtained from the obj file generated by the 3D scanner. :)

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Quote:
 Original post by EnigmaI thought I remembered those pictures. You also started a thread three and a half months ago on a related, but not identical topic. I'll just post a link here since some of the things mentioned in the other thread may help people better understand what you're trying to do or what you've tried. Linky.Enigma

Thanks Enigma. Yes, I posted this pics sometime back. All this while, I have been working on this irregular mesh directly. Now I am considering turning this irregular mesh to a regular one before working it in hope of getting a more stable simulation.

[Edited by - Mystery on December 2, 2004 10:08:30 PM]

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Quote:
 Original post by MysteryThanks for the reply. Is there any link which elaborate more on of your above method. I am pretty new to this so will need more details in order to implement it.Btw, the structure is not really exactly flat. Here is a cross-sectional view of it.

If you rotate the sheet slightly to the right, you will be able to get a heightmap. Even without rotation, it might work. It doesn't need to be exactly flat, it is just required that there are no overhangs.

I don't have implementation notes on this (since I just thought it up), but the biggest part will be to find the outer perimeter and to move the regular-grid-nodes to that perimeter. But since you it's a preprocessing step (I guess), it doesn't need to be fast. Maybe you can even do that by hand if you only need to do it once.

Lutz

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Quote:
 Original post by MysteryThanks Enigma. Yes, I posted this pics sometime back. All this while, I have been working on this irregular mesh directly. Now I am considering turning this irregular mesh to a regular one before working it in hope of getting a more stable simulation.

IS this something you have to do? i mean, use the 3dscanned version.
If i where you i would load that mesh into maya or lightwave and then while using that as a reference model, i would create a new mesh that is more regular than the first one.

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