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Precision Sculpting

For organic and simple shapes, basic sculpting techniques are usually adequate. However, you can make complex and highly precise sculpts with the tools available with Blender, some advanced knowledge, and a little bit of patience.

Precision sculpting techniques can be used for creating:

Smooth, professional-looking archways
Complex, geometric shapes, like gears
A single scultie that looks like multiple objects (see this tutorial)
Any other shape that needs to be highly accurate

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There are 256 possible values for every color channel in an RGB image, and so, there are 256 location values for every axis on a sculpt map.

The Theory

You already know that a sculptie's shape is defined by an image's RGB values.

Consider this:

How many values are available in an RGB image. The total number is quite large, but for each individual channel, the answer is 256. Values range from 0 to 255.

So. Translate this to your sculptie. How many locations are available for the points of your sculpt map. It's the same number as the available RGB values. There are 256 available location-values for each axis of your sculpt.

Think of it as a 3-Dimensional grid. 256 x 256 x 256. Then think of a 'snap to grid' function. If the points of your sculpt don't fall on one of these grid points, when you bake your sculpt map, the points will be put at the NEAREST possible point. For most organic sculpties, this is fine, but if you need a precise sculpt, often this will put points far enough off the mark to make the sculpt look... bad.

Note: You decrease the number of available locations when you decrease the contrast of your sculpt to 'shrink' it, as this eliminates a good number of the RGB values that get used.
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Change the Blender grid to:

Spacing: 0.01
Lines: 60 (not important)
Divisions:1

Change the dimensions of your mesh's object to 2.55 x 2.55 x 2.55, then line it up to the grid.

Duplicate your object, but place the duplicate right on top of the original. This will be your shape reference.

Now go into edit mode and place all significant vertices at points where the edge of the shape reference intersects with points on the grid. (significant vertices are those that define the shape of your sculptie.)

The Practice

So what we are going to do is actually set up this grid in Blender. Then, when we have the sculpt finished we can snap all the vertices to the grid, so that every vertex will be placed exactly how it will be when imported into Second Life.

For this part of the tutorial, open up a .blend file with a sculpt mesh that you would like more precision on. For the purposes of this tutorial, try to use a sculpt that is relatively simple, and has some sort of curve to it. Something like an archway or the hood of a VW Beetle would be good. I'll be using the beveled archway shown above.

Go to the menu below your 3D View window and navigate to View > View Properties. In the dialog that pops up, change the Grid Spacing to 0.01 and the Divisions to 1.

Make sure that you're in Object Mode and select your sculpt mesh object. Then go to the menu below your 3D View window and navigate to Object > Transform Properties. Alternatively, you can just tap N.

Change the dimensions of your object to 2.55 x 2.55 x 2.55. This will probably make your mesh look distorted, but what we did here is make it so that each .01 grid space represents a value on each 0-255 axis. At this point, my beveled arch looks like this.

Lastly, you want to place a corner of your mesh on the grid. Find a point on your mesh that makes a good "outer corner" of your mesh, such as one of the bottom ends of my arch. Zoom in so you can see the grid, then line up the corner with one of the grid points ( as shown here).

Q: Why not make the grid 1.0 units and make the mesh 255 ^ 3 units large?

A: a 255 unit mesh would be rather unwieldy. You'd have to zoom out a LOT to see the entire thing, and often times, having the mesh that large just turns into a mess. 2.55 is a lot easier of a size to work with, so we make our grid 0.01 units large.

Now, if I was to snap the vertices to the grid right now, the results would look something like the mesh on the right:

You can see how the lines of vertices become rough. If I had exported a sculpt map from the mesh on the left, this 'roughing up' is exactly what would have happened. So what do we do? We perform an exercise in patience. We place our vertices on the grid BY HAND!

Don't worry. You don't need to place every single one on a grid point. Just the ones that are significant to defining the form of your mesh. For example: On my arch, the vertices that define the form the most are the ones that make up the top and bottom edges. The ones in between aren't so important.

Shape reference

In order to make things slightly easier, I'm going to make a duplicate of my object that will act as a shape reference for my final piece.

Go into Object Mode (TAB). Hit SHIFT-D to duplicate, then RClick to place the duplicate mesh at the same location as the original. Now go back into Edit Mode (TAB again).

In this image, I've pulled one of my 'significant' vertices down so you could see the shape-reference line provided by the duplicate mesh.

What I want to do is place the significant vertices at points on the grid that intersect with the shape-reference line (such as the point marked with the yellow arrow.

Do this for all your significant vertices.

In the end, your mesh may look something like the image on the left. I have marked all of the vertices which I placed on the grid. All other vertices shown were placed arbitrarily.

After you have this done snap your vertices to the grid again, then bake your sculpt map.

The vertices kinda look like a mess, yeah, but in the end, you keep the shape of your object better than if you had left your mesh in it's original state. To emphasize my point, and also show off what precision sculpties can do, here is a screenshot of my finished sculptie in Second Life, below it's closest equivalent made with regular prims. You can click the image to see it larger:

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Tips and Tricks will be updated as I learn them.

Tricks:

Use a Mirror Modifier to cut down work on symmetrical sculpts.

Tips:

Add the precision grid to your Default Settings so you don't have to constantly change the View Settings.

Notes:

Shrinking a sculpt by decreasing the contrast in Photoshop effectively decreases the number of possible placement values available for your vertices. If you plan on using this trick, you need to adjust the size of your mesh in Blender to reflect the number of values you shave off your sculpt.

Tricks, Tips, and Notes

I'm still learning about precision sculpting, but as I gain tips and tricks for making precision sculpting better and faster, I'll add them here.

Trick: Mirrored Halves

If you have a precision sculpt that has symmetrical halves, you can cut down on some of the placement work by using a mirror modifier. (Click here to learn how.)

With the mirror modifier in place you can go through and place the vertices on the one half of your sculpt, and the modifier will do the other half for you.

After you've applied the modifier, double-check that the sculpt's dimensions are still 2.55 units cubed. Now snap your vertices to the grid, then export the sculpt map.


Tip: Default Settings

If you find that you're using the precision grid very often, you can add the grid to your Default Settings. Just set everything up how you want it to look when you open up Blender, then navigate to File > Save Default Settings.


Note: Shrinkage Resolution Trick

If you've already read my tutorial on Resolution Tricks, you'll probably remember the section on shrinking a sculpt. When you do this, you are giving up a chunk of your possible placement points.

For example: If, in the Levels dialog, you put the sliders to 50 and 205 (default is 0 and 255) You are taking off 100 possible placement values for each axis. If you know you'll have to do this resolution trick, plan ahead. Instead of sizing your mesh to 2.55 cubed, you'll have to size to 1.55 cubed.

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Remember to play around with what you've learned. Experiment. Be adventurous. Make mistakes.
Nothing in Blender is precious.

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