Check BlandShape Normal¶

Since Unity 2018, when importing fbx into Unity, the BlendShape normal is automatically recalculated. As a result, there is a possibility that artifacts are produced on the model’s surface.

Details

If the BlendShape normal is (0, 0, 0), the value of the surface normal should not be changed. It seems that the original BlendShape normal is replaced by the recalculated BlendShape normal, resulting in unexpected changes on the model’s surface

Validate surface normal using MToon’s debugging options¶

Drag fbx to the Hierarchy window and select it. In the Inspector, click Select -> Materials -> Extract Materials and choose a folder to save these materials.

Next, select all materials

and change Shader to VRM/MToon.

Surface normal validation

At this point we set all the materials to MToon for surface normal validation only, so setting up textures’ properties is not required.

To visualize the surface normal, go to Options - Debugging Options - Visualize and select Normal:

../../_images/mtoon_normal.gif — debug normal¶

Select a GameObject containing SkinnedMeshRenderer with BlendShape. Drag the slider while observing surface normals:

We can see surface normals around nose tip and mouth are not correct.

../../_images/broken_normal.jpg — debug normal¶

Surface normals around the norse tip
and mouth (e.g. tongue, lower lip)

are totally different

モデル情報

vroid さんの vrm を blender に import
blender から fbx export
unity に import

したものです。

BlendShape の法線をなおす¶

上記の方法で BlendShape がおかしいことが分かった場合に修復する方法。

fbx の Model タブを選択。

Legacy Blend Shape Normals をチェックして Apply。

../../_images/legacy_normal_fixed.jpg — fixed normal¶

BlendShape がなおっていることを確認します。

修正前との違い

鼻先、下唇に加えて、舌が全然違う法線になってます。