Describes: applying brushmaps, changing projection mode, resizing, moving, restricting their application to surfaces.
Brushmaps are an invaluable tool when it comes to photorealistic rendering. Not even the most sophisticated procedural textures can reproduce the complex details of natural imagery.
Add a plane and select it. Open Images Panel and load the image "People/ Paola2.24". Accept Images Panel and open Materials Panel. Select the image just loaded from the Available Images list and click on the transport gadget ">>" to apply it to the surface. The brushmap will be applied by default in color mode and with a planar projection, the preview sphere will show the resulting image.
Map (left) is compressed to fit the square plane
Go back to the editor, switch to Photorealistic preview and have a look at the resulting image. Since the image was taller than large, it has been compressed to fit the square plane.
This happened because all brushmaps are considered varying in size from 0.0 to 1.0 regardless of their real proportions and the same happens to surfaces. The brushmaps axes are called U and V to differentiate them from the X and Y axes used when dealing with object's geometry. There is also a third axis, W, that aligns with Z and is only used with procedural textures.
Editing U and V Tile
To restore the correct proportions, reopen Materials Panel and edit the V Tile value, setting it to 0.5. Preview the result. The image looks much better.
The brushmap scaled by 0.5 on V fits the square
Lowering the 1.0 default in V Tile has effectively scaled by 0.5 (that is, divided by 2.0) the V axis size, apply ing only the top half of the brushmap to the entire square.
Now try increasing U and V Tile, setting both to 2.0. Preview the result. Since we have increased the U and V axis size, the brushmap has been enlarged. Two dimen sional brushmaps, however, do have a finite detail, and there is nothing outside their boundaries. Therefore the image has been replicated or tiled (hence those value's names) along the surface.
Tiling displays multiple copies of the brushmap
Editing U and V %
Now experiment with the % U and V values. Those two controls act much in the same way as the Tile ones, but instead of scaling the maps they move their origins. Set U % to 0.25 and preview, the tiled image above will appear to have shifted to its left. Use a negative value and it will move to its right. The same happens varying V but along the vertical axis.
Both axes are shifted by 0.25, imagery gets replicated
Just like before, since brushmaps do not have infinite detail, the imagery that "exits" on one side gets replicated at the opposite one.
Planar Wrapping
Now save the plane on disk as we'll use it again, then delete it from the workspace and add a cube. Enter Materi als Panel, apply the same map used before to the cube and preview the result rotating it in perspective.
Only one plane is defined in planar mapping
The front and back face of the cube will be textured correctly while the others will show garbage or streaks. This is because there is not a third dimension associated to two-dimensional brush maps. In order to texture a different face of the cube we can use the cycle gadget that reads Front +Z in Materials Panel. Setting it to Top +Y will texture the cube's top face, Right +X will texture the right face and the negative variants (-Z, -X, -Y) will texture the opposite faces.
Cubic Wrapping
We may want, however, a more sophisticated wrapping method that applies the same brushmap to the entire surface, rotating and reflecting it so that all the faces are textured at once.
Click the cycle gadget that reads Plane until it reads Cube and accept (note that the Front, Top, Right settings are now ignored). Preview the resulting image, the cube is now properly textured on all of its faces.
Cubic mapping defines all six planes
Even if the wrapping method is called Cube and we applied it to a cube, it can really be used on any object and provides for a very easy way to add a basic brushmap to an object.
Spherical Wrapping
Now delete the cube and add a sphere. Apply to the sphere the usual map and preview it. Since the wrapping mode is planar, the sphere will be covered with a slightly curved image, just like if we had projected a slide over a white ball. This is clearly not what we want if the brush map represents the entire surface of the sphere, for example to wrap a map of Earth's lands and seas to create a planet.
Planar and Spherical wrapping onto a sphere
Change wrapping to Sphere and preview again, now the whole sphere has the image shrink-wrapped (and deformed) over its surface. Try also changing the applica tion axis, to see how the wrapping rotates and the sphere's "poles" get placed along the different axes. An easy method to remember how spherical brushmaps are wrapped around axes is to think to the selected axis as the one where the rear seam of the brushmap appears.
There is no way to wrap a planar surface onto a sphere without distorting it at the poles. Cartographers were confronted with this problem for centu ries. The only solution is to account for the distortion when the map is painted, and Meshpainting is invaluable for this. Also, maps used for spheri cal wrapping should be twice as large than they are tall.
Tubular Wrapping
Delete the sphere and add a Tube, apply to it the brushmap and select Tube wrapping, Top +Y. Preview as usual, this time the wrapping will appear to follow the curved surface of the tube, while remaining straight along the vertical axis. Depending on how the tube is oriented, the Front, Top or Right axes can be chosen. The chosen axis determines along which axis the map remains straight.
Wrapping the map over a tube's surface