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  1. #21
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    Default Re: How could I model this?

    It's very doable in Rhino, and there are multiple ways to accomplish it.

    Make a sphere.
    Draw some curves on a side view to where you want the growth rings. You probably want the winter wood to be thin, and the summer wood to be thick for a realistic effect.
    You can use wirecut to slice the sphere into slices. The result will be polysurfaces. (The original surface was only a single surface.)
    You can use scale2d to resize the winter wood slices to make them a little smaller.
    If I were going to make a mesh with the result, and wanted the result a single polysurface, you can union the slices again.

    As long as you are careful with the slices and the unit accuracy is not dauntingly high, Rhino should be able to union the slices.
    But if the union fails, because you are resizing sections, you may cause nearly coplanar surfaces which may be difficult to union.
    You may have to keep the unit accuracy moderate and not .000001mm, or make sure the slices interfere with one another.

    ~

    Another way to go about it is to create a displacement or height map with you can deform a section like a half of the sphere at a time. The advantage here is you can include endgrain in your result.
    Though, you are going the be throwing a lot of nodes in the result.

    ~

    A 3D scanner can scan the surface and create a detailed triangle mesh that could be imported into Rhino as well, though you would be limited to what a triangle mesh could do. Still, you could merge your NURBS geometry and the triangle mesh on export, so when you carve, you can have it.



  2. #22
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    Default Re: How could I model this?

    Okay, brace yourself because this is a long tutorial on how to make this, such that it looks like what you want, is a closed polysurface, is editable (to a degree) and looks wood-like.
    Please accept my apologies if my tutorial has some issues, as I wrote the steps as I did them, and did not really proof-read it much.

    1. create SPHERE (using top viewport)
    How could I model this?-woodgrain-sphere-1-jpg

    2. create a BOUNDING BOX around the sphere.
    How could I model this?-woodgrain-sphere-2-jpg

    3. use the vertical left edge (front viewport)
    to create a LINE (Project mode is on)
    How could I model this?-woodgrain-sphere-3-jpg

    4. use DIVIDE to get some even segments to use as a base for your woodgrain lines. Gauge about how many you might need to get the look you want.
    How could I model this?-woodgrain-sphere-4-jpg

    5. draw a long LINE across the uppermost
    dot from the segment divisions. Ensure that it goes past the right side of the sphere (at this point, you may want to turn on persistent Record History so that you can fine-tune some stuff later)
    How could I model this?-woodgrain-sphere-5-jpg

    6. ARRAY that line downwards using the other dots as your array parameters (use point snap to snap to the leftmost points
    How could I model this?-woodgrain-sphere-6-jpg

    7. PROJECT the curves on to the sphere surface, from the FRONT viewport. Now you have some circles around the sphere.
    How could I model this?-woodgrain-sphere-7-jpg

    8. COPY the horizontal lines from earlier, now these will be rail curves for the next step.
    How could I model this?-woodgrain-sphere-8-jpg

    9. draw some control-point CURVEs on the lines from step 8. you can make them as detailed as you want. Do not overlap these.
    How could I model this?-woodgrain-sphere-9-jpg

    10. use the COPY command to copy the curves you just created so that they're next to the originals.
    How could I model this?-woodgrain-sphere-10-jpg

    11. use the MATCH command to make the endpoint of the first set of lines match the contour of the copies. Once you're done, you can delete the copies.
    How could I model this?-woodgrain-sphere-11-jpg

    12. remember the sphere? create a slightly smaller sphere now. don't delete the other one, just hide it. This is your TRUE sphere. Once you're done, you can resize this object.
    How could I model this?-woodgrain-sphere-12-png

    13. use the FLOW command to wrap your controlpoint curves around the circles surrounding the sphere. Toggle on the "Stretch" function within the flow command, and use the straight lines as your base curves. You may hide the lines, circles, and original controlpoint curves (you may want to edit them later if your wood grain isn't up to your liking, so don't delete them; put them in another layer if you need them out of the way)*.

    *note that since Record History is ON, you can edit the structure of your surfaces by editing those curves you originally created. Editing the curve will edit the flowed curve, and the surface patches as well. Just stay away from the points closest to the endpoints. If you must edit those, you will have to re-match the curve (step 11) if you want your surface to look nice.

    How could I model this?-woodgrain-sphere-13-jpg


    14. use the PATCH command once for every wobbly circle. You can set the U-Spans/V-Spans to 20 or so, so that there's lots of nice flowy structure on your surfaces.
    How could I model this?-woodgrain-sphere-14-jpg


    You are probably beginning to see in you mind, some options as to how do do the next steps, but we're going to try using split for this version.

    NOTE: If you haven't gotten your lines exactly how you want them by now, this is the time to do all your edtis, because after this, it's all about joining surfaces and extrusions, etc.

    15. SPLIT the sphere using your patch surfaces as cutters. Once done, Copy&Paste all the surfaces to another layer. Hide your original layer.
    How could I model this?-woodgrain-sphere-15-png

    16. SPLIT your patch surface copies using your split sphere. Delete the outer excess. If any surfaces don't want to split (Rhino bug?), use INTERSECTION to find the line where the surfaces intersect, and use that line to TRIM the surfaces.
    How could I model this?-woodgrain-sphere-16-png


    17. HIDE the sphere briefly, and PASTE another copy of those trimmed surfaces. If you lost your clipboard objects, you're going to have to EXTRACTSRF off of the closed surfaces, then re-close them. Then, use EXTRUDESRF to give them some thickness. Start from the north hemisphere and extrude toward the equator, for all surfaces north of it. Do the opposite with the southern surfaces.
    Do not do this to the 'widest' surfaces (those at the equator). Delete the original surfaces.
    How could I model this?-woodgrain-sphere-17-png

    18. use the SHOW command to show your hidden split sphere surfaces. Use the JOIN or BOOLEANUNION command to join each splitsphere shape to its corresponding southern polysurface. You may have to remove duplicate surfaces using EXPLODE, EXTRACTSRF, etc. depending on how you joined everything earlier. You also may have to copy your patch surfaces and move the copies in order to close everything.

    How could I model this?-woodgrain-sphere-18-png

    19. Use the FILLETEDGE command to add a small fillet to every polysurface's upper edge if they're north of the equator, and every lower edge if they're south of it. The center/equatorial surface will be filleted on both sides. Sometimes the equatorial surface requires a smaller radius otherwise it looks like a bigger cut. Oh, and the two radii that are closest to each other on the equator should be different values, otherwise you might have trouble joining these polysurfaces later.

    How could I model this?-woodgrain-sphere-19-png

    20. You should be able to BOOLEANUNION these surfaces. If you cannot, draw another smaller sphere inside of these, and, one by one, join everything until you have one object. If you have software that will unify your surfaces, just export the STL at this time, and unify the surfaces there.

    How could I model this?-woodgrain-sphere-20-jpg

    And there you have it!
    You You can add knots by using 3d objects such as ellipsoids, and flowing them around your original circular wobbly lines. Or, just draw the ellipsoids and insert them such that they're inside your sphere, then do a boolean difference and fillet both edges as we did. Up to you.



  3. #23
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    Default Re: How could I model this?

    Apologies for the extremely late reply but thanks Jorge-D-Fuentes, this worked a charm!



  4. #24
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    Default Re: How could I model this?

    Congratulations on getting a desired result!



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How could I model this?