Doc:Manual/Modelling/Meshes/Advanced Tools

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Manual - Blender 2.4

Advanced Mesh Modelling

Symmetrical Modelling

A plane.

You often need to model objects which exhibit some sort of symmetry. For radial, rotational or multiple symmetry the best approach is to carefully model one base structure and then, as a last step, duplicate the base cell via Spin Dup or whichever command is most appropriate. For objects with bilateral symmetry, those with one plane of symmetry, such as most animals (humans included) and many machines, the above method implies modelling one half of the object, and then mirroring a duplicate of the first half to get the whole object. Since it is usually difficult to attain correct proportions by only modelling a half, it is possible to duplicate the half before it is completely modelled, and act on one half and automatically update the other.

Right half.

In Front View add a plane or whatever (A plane). Consider it as a starting point for one half of the object. Let’s say the object’s right half, which for us in frontal view is on the left of the screen. The plane of symmetry is the yz plane. Move the mesh, in Edit Mode, so that it is completely on the left of centre. Delete some nodes, and add some others, to give it its general shape, as in (Right half).

Mirroring the linked duplicate.

Now switch to Object Mode and, with the half selected, make a linked duplicate with AltD. Press Esc to exit from Grab Mode and press N. In the Numeric input panel which appears, set SizeX to -1.0 (Mirroring the linked duplicate). This effectively mirrors the linked duplicate with respect to the Object’s centre, hence the importance of keeping the centre on the plane of symmetry.

Editing one half.

Having duplicated the Object as a linked duplicate implies that the two objects share the same mesh data, which is implicitly mirrored by the unitary negative scaling along the x axis, which is normal to the symmetry plane. Now you can edit either of the two halves. Since they share mesh data any change, be it an extrude, delete, face loop cut etc… immediately reflects on the other side (Editing one half).

By carefully editing one half, and possibly by using a blueprint as a background to provide guidelines, very interesting results can be achieved.

A head. Left: EditMode; Centre: ObjectMode; Right: Joined.

As a final step, when symmetrical modelling is complete, the two halves must be selected and joined into a single Object (CtrlJ). This makes the seam (very visible in A head. Left: EditMode; Center: ObjectMode; Right: Joined., centre) disappear. Once you have a single object (A head. Left: EditMode; Centre: ObjectMode; Right: Joined., right), you can start modelling the subtle asymmetries which every being has.

Noise

Noise button in Editing context.

The Noise function allows you to displace vertices in a mesh based on the grey-values of a texture applied to it. So, you have to have a texture assigned to the material, even if that texture is not Mapped To anything. In your texture, you should enable No RGB to convert colour textures to a gradient. You should also have subdivided your object enough to have many vertices to act on.

Use Noise to generate great landscapes or make mesh surfaces more real-world (pitted, un-smooth). The Noise function displaces vertices in the object’s Z-Axis and negative Z-Axis only. To deform your mesh’s other dimensions, simply rotate your object and apply rotation, or rotate the vertices in edit mode, and apply Noise. Then, rotate it back again to get your original orientation.

Noise permanently modifies your mesh according to the material texture. Each click adds onto the current mesh. For a temporary effect, map the texture to Displacement for a render-time effect. In object/edit mode your object will appear normal, but will render deformed.

	Use modifier!:
	The recent Blender versions have a much more flexible tool to realise this sort of effects: the Displace modifier. You are strongly encouraged to use it rather than the Noise tool – some of the key advantages of the modifier are that he can be cancelled at any moment, you can precisely control how much and in which direction the displacement is applied, and much more…

Example

Subdivide tool.

Add a plane and subdivide it at least five times. To do that you can either use the Subdivide or Subdivide Multi entry in the Specials menu accessed via W; see (Subdivide tool). Using Subdivide Multi is faster and easier. Select Subdivide Multi and enter 5 for the Number of Cuts popup dialogue.

Now add a material and assign a Clouds texture to it. Adjust the NoiseSize: to 0.500. Choose white as the colour for the material and black as the texture colour, to give us good contrast for the noise operation.

Ensure that you are in Edit Mode and that all vertices are selected, then switch to the Editing Context F9. Press the Noise button in the Mesh Tools Panel (Noise button in Editing context) several times until the landscape looks nice. (Noise application process) is an example of applying the noise tool, showing the original – textured – plane as well as what happens as you press Noise. From top left to bottom right: Plane with texture, sub-divided plane, Noise button hit 2, 4, 6 and 8 times.

Noise application process.

Remove the texture from the landscape now because it will disturb the look. Then add some lights, some water, smooth the terrain, and so on (Noise generated landscape).

Noise generated landscape.

Manual