Mirrored & Non Mirrored Patches

By default when we create a model, all the patches will be mirrored, this means the left side will automatically mirror the right side when we drag control points, insert control lines or extrude points. This is what we are likely to want when getting started making a head, body, animal, car, train or plane but for making something like a tree or a house we will likely want to begin with non mirrored patches. To get started creating a non mirrored model we just need to toggle to before adding a starting node such as a lathe, box or sphere to the scene.

Avoiding Mirrored & Non Mirrored Patch Combination Issues

A model can contain both mirrored and non mirrored patches without any issues if all the mirrored patches are only stitched to mirrored patches and all the non mirrored patches are only stitched to non mirrored patches.

In the case where we have mirrored patches stitched to non mirrored patches, we should avoid inserting control lines or making extrusions as this will likely cause the automatic stitching to fail.

We can set all our patches to being non mirrored at any time but setting non mirrored patches to mirrored will cause problems (unless we are creating paired mirrored patches from the non mirrored patches), if the patches are no longer set up correctly for mirroring which can happen after control lines have been inserted or extrusions have been made while the patches were non mirrored.

Changing the Mirror State of Patches

A patch's mirror field specifies if a patch is mirrored or not. We can set this field directly by clicking the check box or by selecting the patches we want to set in the 3d window using the rectangle selection tool and then clicking modelling-menu-button and selecting mirror selected patches or un-mirror selected patches from the menu.

Paired Mirrored & Single Mirrored Patches

Mirrored patches can be single or paired. With paired mirrored patches there are always 2 patches, one for the left side and one for the right side. Each of these patches will be the mirror opposite of its paired patch but with single mirrored patches the left or right side will be the mirror opposite of it's other side within the one patch. Patches are paired by having identical names except for their mirror prefix, l_, r_ for example:

Alternatively they can be prefixed with a lower case r or l immediately followed by an upper-case character for example:

Paired mirror patches should always have their insideOut field the opposite state of their opposite patch so that the visibility of the triangles are matched for both patches.

Creating Paired Mirrored Patches From Non Mirrored Patches

We can easily create paired mirrored patches from non mirrored patches if the patches we want to duplicate in mirror form are only on one side. First select the patches we want to duplicate using the rectangle selection tool and then click:


This will result in all the selected patches being mirrored and paired with the duplicated patches:

Any control points that meet the other side exactly in the centre can easily be selected and stitched:

This example highlights how paired mirrored patches can easily be converted to non mirrored patches and converted back at any time to mirrored patches by deleting one half of the patches and then duplicating the other half back.


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