3D Mesh Cleanup Tutorial: Fossil Crab (Advanced)

Import the crab into Meshlab by following Part 1 in the Cupule Cleanup Tutorial.

The imported mesh includes the crab, but it also includes other small isolated meshes that are 3D reconstructions of bits of the matrix. Remove this external debris by running a filter that removes small isolated mesh particles.

Go to Filters > Remeshing, Simplification and Reconstruction > Remove isolated pieces with respect to face number .

This option may be under “Cleaning and Repairing” in other versions of the software. As the 3D mesh of the crab is a large connected mesh with a relatively high number of faces, start by removing meshes with a relatively small number of faces (e.g., 200) and increase incrementally (e.g., by 50-500) until the bulk of the isolated extraneous mesh pieces are removed.

The scene still contains a few relatively large bits of extraneous isolated meshes. To select and delete these faces manually, first click on the Interactive Selection tool in the top right of the icon-based menu.

Hold left click and drag your cursor to select faces.

To add faces to your selection, hold command (Mac) or ctrl (PC) while you left click and drag . To delete faces from your selection, hold shift while you left click and drag .

Delete these faces by deselecting the Interactive Selection tool and selecting“Delete Selected Faces and Vertices” on the right of the icon-based menu.

Next, repeat these steps to select and delete the small, rounded pebbles that are touching the crab mesh.

Note

Note that your selection goes through the entire mesh in that plane of view. Be sure to minimize the number of faces of the crab mesh itself that are deleted; this can be done by turning off the Interactive Selection tool

and rotating the mesh to ensure no pieces of the crab mesh were accidentally selected before deleting mesh components. We recommend duplicating the mesh, as Meshlab does not have an undo function, in case desired components of the mesh are accidentally deleted or deselected.

Duplicate the mesh by right clicking the file name and selecting “Duplicate the Current Layer.” Select the eye icon on the original layer to toggle visibility so you can see deletions on the new layer more clearly. You may wish to delete extraneous mesh little-by-little as you are just beginning, as opposed to all at once (as shown in the image below).

Clean up the mesh by selecting Filters > Remeshing, Simplification and Reconstruction > Repair non Manifold edges . Select Remove Faces and click Apply .

Then, remove small isolated pieces that might have been formed during previous steps repeating Filters > Remeshing, Simplification and Reconstruction > Remove isolated pieces with respect to face number . Save this mesh layer by duplicating it.

Close holes that formed in the crab mesh during the deletion of articulating debris by selecting Filters > Remeshing, Simplification and Reconstruction > Close Holes . Set “Max size to be closed” to 500 and select Apply . Alternatively, holes can be patched via the sculpting method described in the previous tutorial.

Deselect everything by selecting Filters > Selection > Select None .

Now, we’re going to shrinkwrap a copy of the crab mesh to fill the leftover holes and smooth the surface of the crab.

The first step to do this is to hollow out the inside of the mesh. Duplicate the mesh and select Filters > Color Creation and Processing > Ambient Occlusion. Keep default settings selected click “okay” on the popup window . This tags the external faces white and internal faces dark.

Next, select Filters > Selection > Select by Vertex Quality . Check preview selection . Move the sliders to set Min and Max to optimize the highest number of internal faces and minimal external ones (e.g., Min at 0 and Max at 0.132944) (review cupule tutorial for details) . Click “Apply.”

Select Filters > Remeshing Simplification and Reconstruction > Surface Reconstruction: Screened Poisson.

Check “Pre-Clean” and click Apply .

This new version of the mesh has filled holes and a smooth surface; however, some detail has been removed. Merge the new Poisson mesh with the mesh saved previously by making these two meshes visible and hiding any others by selecting the eye icon.

Right click one of the meshes and select “Flatten Visible Layers” to create a merged mesh . Keep default settings selected.

Save this mesh by selecting File > Export Mesh . Name the file “Body remesh.” A new pop-up window will appear. Select “none” in the bottom left corner and click “OK.”

To simplify your scene and get rid of unwanted meshes, close and restart Meshlab. Reopen Crab before.obj in Meshlab.

Position the left eye of the crab at the center of the project window by holding Command (Mac) or ctrl (PC) and dragging the mesh , or holding down the scroll wheel and dragging on a mouse.

Zoom in using the scroll wheel on the mouse.

Select the eye using the Interactive Selection tool (

).

Select everything except for the eye by selecting Filters > Selection> Invert selection . Check both Invert Faces and Invert Vertices, and click “Apply.” All of the mesh components except those of the eye will be selected in red.

Delete selected faces and vertices

Shrinkwrap the eye. Perform the ambient occlusion filter and delete the internal vertices. Save this mesh by duplicating it. (See “Shrinkwrap surface” section for details.)

Apply the Surface Reconstruction: Poisson Remesh. Enter 4 into the “Reconstruction Depth” window.

Merge the two meshes of the eye created here. Perform a Poisson Remesh of this new mesh: enter 5 into the “Reconstruction Depth” window. Export the file as “Eye remesh.”

Close and restart Meshlab. Import and merge “Body remesh” and “Eye remesh”.

Select the leg that's isolated from the rest of the body.

Copy the mesh.

From the original mesh, invert the selection and delete the rest of the body.

Export this mesh “Leg remesh.”

In the copy of the mesh, delete the leg. Export this mesh as “Crab body and eye remesh”.

Open Maya.

Import “Crab body and eye remesh.obj” and “Leg remesh.obj” into Maya by going to File > Import and selecting these files.

Click “A” to view all imported files. To rotate through the scene, hold “Alt” and left click while dragging the cursor.

On the lefthand side of the screen, there are tools for moving, rotating and scaling the objects within the scene.

One of them is the transform tool:

And another is the rotation tool:

Click on the leg, and use these tools to transform and rotate the leg to reattach it to the body of the crab.

Now, we’re going to make a copy of the left eye to use as the right.

Reopen “Crab body and eye remesh.obj” in Meshlab.

Select the eye.

Invert selection and delete the body, leaving only the eye.

Export mesh as “Eye remesh 2.obj”.

Import “Eye remesh 2.obj” into Maya.

To mirror the eye, first, select the scale icon on the left:

Click the icon to the right of the X, Y, Z in the first icon-based menu at the top of the screen and set to “Relative transform”.

Type -1 into the Z box and push “Enter”.

Select the newly mirrored eye and move to the correct location on the crab using the transform and rotate tools.

Next, select all mesh components by clicking the selection icon, holding left click and dragging the cursor over all of the objects. Command A also works.

Select Mesh – Combine in the first menu at the top to merge all mesh components together.

Repeat the Repair Missing Elements protocol for the eyes to fix the tip of the claws and legs. Congratulations on making a beautiful crab!