This tutorial describes one way to make sculpt textures from a mesh for use as "sculpties" in Second Life using Blender 2.43. If you have never used Blender before, consider looking at the many starting tutorials on the Web to familiarise yourself before diving into this.
The method described here has been pieced together from discussions on the Second Life wiki and by trial and error.
Step 1. Create a cylinder to use as the mesh. The default 32 vertices works well.
Step 2. Delete the single vertex at the top and bottom ends of the cylinder. If you are using Blender 2.44, you can also skip this step by choosing not to cap the ends when creating the cylinder.
- Explanation: The UV mapping for a sculpt texture must be a regular grid and must fill the entire texture exactly from edge to edge. This conforms with a cylinder that has no end poles (if you visualise this mesh being cut and unrolled and flattened, you can see that it forms a rectangle). Currently, all sculpties conform to this cylindrical topology, which means that certain shapes (such as shapes with holes) cannot be made. Other topologies are expected to be supported in a future version of SL.
Step 3. Select the vertices at the top end and mark them as a seam (Ctrl-E).
- Explanation: The seams tell Blender how your mesh should be sliced up and "unrolled", as we will see later when the UV mapping is created by unwrapping the mesh.
Step 4. Select one of the top vertices, and the vertex at the bottom connected to it, and mark that edge as a seam (Ctrl-E).
Step 5. Subdivide the cylinder horizontally to add some vertices to work with. The Loop Subdivide tool (Ctrl-R) is useful for this.
- Explanation: The vertices of the original cylinder give you the vertical vertex positions in the sculpt texture. The vertices created here provide the horizontal vertex positions. Together, they give you a grid of vertices, which you can later move around as you please to mould into any shape you like, provided you don't add or remove any vertices. One way to think of this resulting cylinder is as a 3D representation of your sculpt texture - moving the vertices around will eventually result in colors in the sculpt texture changing.
Step 6. Open the UV/Image Editor, enter UV Face Select mode, select all the faces (A), then Unwrap the UV coordinates (U).
- Explanation: UV mapping is a way to map between 2D images and 3D shapes. Each vertex in your 3D mesh will have a corresponding 2D UV coordinate, the total of which is represented by the grid of UV coordinates in the UV window.
- Tip: Every viewing area in Blender can be split and set to show another window type. To split a viewing area, right-click on a border of the viewing area and select Split. Then move the split line which appears to wherever you would like the split to be made, and click. You can then set each viewing area independently to another window type using the drop-down button on that area's tool bar.
Step 7. Move and scale the UV coordinates so that they fit as well as possible into the image square.
- Explanation: Because the sculpt texture is a result of the UV mapping of your mesh, the more accurate your UV coordinates are, the more accurate your resulting sculptie will be. Ideally, your UV coordinates will be as evenly spaced as possible, aligned neatly without any jagged coordinates, and fit from edge to edge.
- Tip: Using the UVs -> Layout Clipped To Image Size menu option can make adjusting the UV coordinates easier by confining movement and scaling to the UV image area.
Step 8. Create a new image for the UV texture in the UV/Image Editor (Image -> New). Make the image 64x64. You might want to adjust the UV coordinates here so everything is straight and neatly lined up.
- Explanation: Sculpties are currently limited to 32x32 vertices, which for various technical reasons are achieved most accurately using a 64x64 sculpt texture. Using a higher resolution texture will not result in more detailed sculpties as the sculpt textures are downsampled to 64x64 when the sculptie is rendered in SL.
- Tip: The UVs -> Snap to Pixels menu option will cause the UV coordinates to snap to the nearest texture pixel when moved. This is useful to ensure your UV coordinates are lined up exactly at the edges of the texture and in rows horizontally and vertically.
Step 9. Add a material to the cylinder. Set the VCol Paint mode for the material.
- Explanation: VCol Paint causes the object to be rendered using its UV texture instead of normal shading.
Step 10. Add three textures for the material. Set the Texture Type for all three to Blend.
- Explanation: A sculpt texture is a texture where the Red, Green, and Blue components map to the X, Y, and Z coordinates of each point on an object. To achieve this, we create three textures which we will later set to map between each axis and color. The Blend mode means that the color value of each texture will blend smoothly from one side of the object to the other, which corresponds to mapping the furthest and closest points of the X, Y, and Z coordinates for the object to 0.0 and 1.0 for each color.
Step 11. Set the input and output parameters for the three textures as follows. The important settings are the axis mappings on the input, and the colors and Add mode on the output.
- Explanation: Each of the textures created in the previous step are now set to map from one axis to one color; red to represent X, green to represent Y, and blue to represent Z.
- Tip: Sliders in Blender can be set by clicking and dragging on the handle, or by clicking on either side of the handle to cause the value to "jump" by a step higher or lower, or also by holding down Shift while clicking to directly type in the value.
- Tip: By selecting the Neg[ative] option for the red/X texture, you will find that the resulting sculptie appears to be "inside-out". NightShade Fugu has found a use for this as a way to achieve better looking transparent objects, like glass, by setting the transparency of the "inside-out" sculptie in SL to something higher than zero. This produces objects which have a two-sided appearance while still appearing translucent (compare this to a semi-transparent box prim, in which the faces closest to your camera appear transparent, but the backs of the opposite faces do not appear at all). Note, however, that transparency rendering issues in the viewer are still being addressed, and a future viewer fix may cause this technique to no longer work.
Step 12. Sculpt your mesh as desired. Blender's sculpt mode is lovely here for organic shapes. Here I've unimaginatively created a vase. Note that while the cylinder mesh appears to be more like a tube, and lacking a top and bottom, when rendered in SL the top and bottom will be closed (though ugly; for better control you may want to scale the top and bottom rings of vertices down to one point and shape the ends yourself, perhaps bringing them into the body of the vase to create a true hollow).
- Tip: When building your model, it's a good idea to first move more of the vertices to the areas which will have the most detail. In the vase below, you can see that the region in the middle of the vase only has one row of vertices, while the curved neck has many more. This prioritisation of vertices is what gives you fine control over the detail in a sculptie. Note that the UV coordinates in the sculpt texture do not move, and remain as a regular grid.
Step 13. Switch to the Scene panel and bake the textures into the UV image. If after baking you notice aliasing artifacts in the baked image, try increasing the Margin by 1 or 2.
- Tip: Using the Ambient Occlusion mode instead of the Textures mode will allow you to bake a shading/lighting texture which shadows the corners and crevices of your object quite naturally. This can then be applied to the sculptie as a regular texture to add shadowing. If you want to do this, consider using a higher resolution for the UV image when baking the ambient occlusion map, and a 64x64 resolution when baking the sculpt map.
Step 14. Save the UV Image (Image -> Save from the UV/Image Editor), preferably to a lossless format like TGA rather than JPEG.
- Tip: In fact, don't ever save sculpt textures as JPEG. Lossy JPEG compression will mean that your carefully placed, highly accurate vertex coordinates come out slightly less accurately when decoded as an image, which is then made worse when SL converts it into JPEG2000 format upon uploading. Save and upload sculpt textures as TGA instead (compressed TGA is fine, since it is lossless).
Then simply upload the image to SL, and you have a new sculpt texture!
Click here to get the Blender file used for this tutorial.
Alternatively, click here for Pavcules Superior's sculptie file repository for Blender and non-Blender sculptie-related resources.
Some sculpted prims: