[Blender2.81] Creating fingertips of a photogrammetric model

A photogrammetric model’s hand often has fingers attached and may not be moved easily. In this article, we are going to show you how to adjust your photogrammetric model so that you can move your fingertips.

Introduction

The model’s hand (unprocessed after photogrammetry) before retopology looks like the following. The index finger to the ring finger is stuck together.

指がくっついている

Fingers are attached

When we apply auto-retopology to the whole body, the hands can be taken on an unoriginal shape.

手の形を留めていない

The shape of his hand is not fixed

So, this time, based on the pre-retopology model hand, we will create a hand with all fingers separated so that they can be moved.

Operation procedure

Cut the hand from the pre-retopology model

Roughly select a hand in the pre-lithology model and select “Selection” from the [P] key to separate the part of the hand into a separate object.

手にあたる部分を選択

Select the part of the hand

To make it easier to work with, hide all but the detached parts.

手以外を非表示に

Hide all but the hands

Auto-retopology

The pre-retopology model has a fine mesh that makes it difficult to detach the clinging fingers. Therefore, only the hand part is auto-retopologized again.

First, we export the model in obj format to flow into the Instant Meshes.

With the hand selected, select “Wavefront (.obj)” from “Export” in “File”.

obj形式でエクスポート

Export in obj format

Select “Selection Only” from the “Include” item in the dialog that comes up.

選択部分のみをエクスポート

Export only the selection

Outputs. Import the output .obj file into Instant Meshes.

Instant Meshesへ読み込む

Load into Instant Meshes

For more information on how to do auto-retopology, see the following article.

リトポロジー結果

retopology results

Import the Retopologized hand into Blender again.

obj形式でインポート

Importing in obj format

It is loaded in the same position as the pre-retopology model.

リトポロジー前と後のモデルが重なって表示される

Before and after retopology models are shown overlaid

If you move it to check, you can see that the number of polygons has been reduced. For later steps, put it back in its original position once you’ve checked it.

リトポロジーできた

We’ve got a retopology

Bake Texture

The post-retopology model is untextured. In this state, it’s hard to tell where the original finger breaks are, so we bake the texture once.

See the following article on how to do texture baking.

テクスチャがベイクされた

The textures were baked

Separate the fingertip mesh

Finally, the work of separating the mesh from the fingertips begins. Select multiple vertices on the border of the finger.

人差し指と中指の境目の頂点を選択

Select the apex of the border between the index and middle finger

Press the [V] key after selection to tear off the vertex. As you can see below, the border between the index and middle finger has been slashed (reversed direction of view for clarity).

頂点が切り裂かれた

The apex was sliced open

In this state, there are no faces on the side of your finger, so select the vertex you want to attach a face to, then select “Bridge Edge Loops” from “Edge” at the top of the screen to attach a row of faces.

辺ループのブリッジ

Bridge of edge loops


側面に面が張られた

The sides were flanked

Move the top of the finger and clearly separate the index and middle fingers.

人差し指を離す

Let the index finger go

Repeat with your other fingers. Note that the boundaries of the mesh and the texture may not be aligned.

メッシュとテクスチャがずれている

The mesh and texture are out of sync

When you check the texture in this area, it should look like this.

UV Editingタブから確認

Check from the UV Editing tab

In this case, you can move the texture in the UV editor.

頂点をテクスチャの境目に移動

Move vertices to texture borders

Also, if you create a new mesh, the texture may have a black pattern.

テクスチャに変な模様が入っている

There’s a weird pattern in the texture

This happens when a new mesh is created, and the auto-generated UVs straddle the unbaked area.

UVがテクスチャのない部分を跨いでいる

The UV straddles the untextured area

There are many ways to settle this, but this time I moved it to a skin tone area.

UVを移動させる

Move the UV

The UV alignment will be corrupted by this method, so we will duplicate and re-bake it later to get the correct UV alignment.

全て修正が終わったら再ベイク

Re-bake when you’re done fixing everything

It completes the area leading to the wrist and is completed as follows.

修正完了

Correction completed!

 

Bind to the whole body

As I was working on separating the hands from the whole body, I would integrate them into a full body model.

Yet, if the number of vertices in the joint to the hand in the whole body model does not match the number of vertices in the joint to the whole body model of the hand, it is not possible to connect it directly. This time, the number of apexes of the hand model is clearly outnumbered.

連結部の頂点数が合わない

The number of vertices in the coupling section does not match

With both the full body model and the hand model selected, press [Ctrl]+[J] to merge the objects. This is to make the comparison of the number of vertices in the joint easier.

不要な頂点を溶解する

Dissolve the unwanted vertices

To reduce the number of vertices, select the edge you want to reduce, press the [X] key, and select Dissolve Edges. Then the face is not deleted, only the edges are deleted.

Repeat this, reducing the number of vertices so that the wrists are connected.

When the number of vertices is equal, select one vertex on the whole-body side and one vertex on the hand side, then press [Alt]+[M] to join the vertices and connect them as follows.

手を結合できた

I can join my hands

 

ミラーモディファイア

Mirror modifier

The right hand will be made in the same way. Reverse the left hand with a mirror modifier. The photogrammetric model is not symmetrical on the left and right, so it needs to be adjusted here as well.

ミラーモディファイアを適用

Apply Mirror Modifier

Connect the tops of the hands in the same steps as in the left hand. The left hand requires less work than the left hand because it is done with a somewhat reduced number of vertices.

頂点を繋げる作業

Connect the vertices

We were able to hold hands without feeling uncomfortable.

完成

Complete!

 

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