Houdini 21.0 Muscles & Tissue

Muscles & Tissueのトラブルシューティング

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Note

Vellum Muscles&Tissuesシステムは、レガシーのワークフローを使用しています。 簡略化されたワークフローとレシピのサンプルについては、OtisのMuscles&Tissuesシステムを参照してください。

アニメーション中に筋肉がボーンから外れる

問題

高速にアニメーションするボーンに筋肉がついていけない。

これは、Muscleアタッチメント拘束の Damping パラメータ設定が原因の可能性があります。 どのVellum拘束でも、ポイントの位置は様々な影響(フォース、衝突、Velocityの変更)を受けるため、Vellum Solverはこれらの要因を満たして、最終的なポイント位置、拘束が成功しているかどうかを判断しようとします。 筋肉アタッチメント拘束に適用される減衰率は、筋肉シミュレーションの各サブステップ中、拘束のエネルギーまたは寄与度を軽減するように設計されています。減衰率の値が高すぎると、アタッチメント拘束の寄与度が低下します。

解決策

まず最初に、以下を試してみてください:

  • Muscle End アタッチメント拘束のDamping値を下げます。

    例えば、Damping値が0.01なら、0.001に下げてみてください。

これで問題が解決しない場合は、以下も試してみてください:

Tissueシミュレーションの折り目/皺の領域の品質が低下する

問題

Tissueの皺ができる部分(二足歩行や四足歩行のキャラクタの肘や膝の領域など)に、細長い三角形、Tissueサーフェスの非均一な伸張、四面体の絡みが生じます。

これは、ソルバが極端なTissue拘束vs.衝突設定を解決できないことが原因で起こります(Tissue拘束のイテレーション回数と衝突パスが、大幅に異なる値に設定されている場合など)。このエラーの視覚的な結果として、Tissueでのエネルギーの分布が非均一になります。

解決策

デフォルトのConstraint Iterations値が100、Collision Passes値が10の場合、拘束反復が10毎に1の衝突パスが与えられます。 これらの設定では、拘束は衝突よりも10倍の頻度でポイントを更新するため、拘束が衝突パスより常に優先されるようになります。

Tissueの折り目/皺の結果を大幅に向上させるには、以下を試してみてください:

  • Collision Passesの数を増やします。ただし、衝突は計算処理が重くなります。

  • TissueのConstraint Iterationsと Collision Passes 値の 比率 をできるだけ1:1に近づけます。

  • 別の方法として、Collision Passesの数の代わりに、Substepsの数を増やすのを試すのも良いでしょう。

Muscle Constraint Properties Vellum troubleshooting

Muscle Ends

To...Do this

Visualize your muscle ends attachments to a bone

  1. Create a Muscle Solver Vellum SOP node.

  2. Connect the Muscle Constraint Properties Vellum SOP output to the input1 of the Musclve Solver Vellum SOP. Connect your bones to the input2.

  3. In the Guides tab, select the checkbox for Attachment Constraints, then the checkbox for Muscle Ends.

Fix a muscle end that fails to attach to a bone

Follow the Visualize your muscle ends attachments to a bone procedure to visualize your muscle end issues.

Increase the Distance Threshold parameter in the Muscle Ends tab of Muscle Constraint Properties Vellum SOP gradually until the muscle end attaches to a nearby bone.

Fix a muscle end that attaches to a wrong bone

Follow the Visualize your muscle ends attachments to a bone procedure to visualize your muscle end issues.

  1. Decrease the Distance Threshold parameter in the Muscle Ends tab of Muscle Constraint Properties Vellum SOP to prevent muscle ends from searching too far for attachment points.

  2. Use the Muscle Paint SOP to manually adjust the areas where muscle ends are allowed to attach

    • Make sure the Muscle Paint SOP is placed after the MUscle Constraint Properties Vellume SOP in your node network.

Fix a muscle end that twists unnaturally

  1. Make sure Axial Ramp Correction in Muscle Constraint Properties Vellum SOP is on to help maintain consistent muscle orientation.

  2. Increase the Tangent Stiffness parameter in the Muscle Ends tab of Muscle Constraint Properties Vellum SOP. This also helps the muscle orientation.

Fix a muscle end that appears to be poking out of the skin

  1. Decrease the Compression Stiffness parameter in the Muscle Ends tab of Muscle Constraint Properties Vellum SOP]. This helps the muscles appear less stiff and conform better to the bones.

  2. You can also adjust the Rest Length Scale to a value slightly less than 1 to pull the muscle closer to the bone.

Muscle to muscle

To...Do this

Fix constraints forming between unrelated muscles

  1. Decrease the Distance Threshold parameter in the Muscle to Muscle tab of Muscle Constraint Properties Vellum SOP. This limits how far internal points can search for connections.

  2. Set Attachment Candidates to control which muscles should connect.

Strengthen constraints that detach easily or fail to stay connected during simulation

  1. Increase the Stiffness parameter in the Muscle to Muscle tab of Muscle Constraint Properties Vellum SOP. This helps the connection between muscles become stronger during movement.

  2. Increase the Compression Stiffness parameter in the Muscle to Muscle tab of Muscle Constraint Properties Vellum SOP. A value above 1 makes muscles more resistant to compression.

  3. Increase the Rest Length Scale parameter in the Muscle to Muscle tab of Muscle Constraint Properties Vellum SOP slightly below 1.

Loosen constraints that are too rigid and prevent natural movement during simulation

  1. Decrease the Stiffness parameter in the Muscle to Muscle tab of Muscle Constraint Properties Vellum SOP. This helps the connection between muscles move more freely.

  2. Decrease the Compression Stiffness parameter in the Muscle to Muscle tab of Muscle Constraint Properties Vellum SOP. A value below 1 may help muscles that are too rigid or compressing too much.

  3. Decrease the Rest Length Scale parameter in the Muscle to Muscle tab of Muscle Constraint Properties Vellum SOP slightly above 1.

Muscle to bone

To...Do this

Fix muscles that are too stiff and lack secondary motion

  1. Decrease the Stiffness parameter in the Muscle to Bone tab of Muscle Constraint Properties Vellum SOP. This helps the connection between muscles move more freely.

  2. Increase the Damping parameter in the Muscle to Bone tab of Muscle Constraint Properties Vellum SOP. This allows for the attachment to appear more syrupy and the muscle appears to swim towards the bones rather than follow them directly.

    • If the muscles are more towards the muscle ends, Increase the Damping parameter in the Muscle Ends tab of Muscle Constraint Properties Vellum SOP.

  3. Increase the Slide Rate parameter in the Muscle to Bone tab of Muscle Constraint Properties Vellum SOP. A higher slide rate allows the muscle to move more naturally over the bone.

  4. Decrease the Velocity Blend parameter in the Velocity Blend tab of Muscle Constraint Properties Vellum SOP to around 0.2 to 0.5. This should be your last resort after trying the other steps.

Collisions and velocity blend

To...Do this

Fix muscles that lag behind fast moving bones

  1. Increase the Stiffness parameter in the Muscle to Bone tab of Muscle Constraint Properties Vellum SOP. This helps the connection between muscles move more freely.

  2. Decrease the Damping parameter in the Muscle to Bone tab of Muscle Constraint Properties Vellum SOP. This allows for the attachments between muscles to respond quicker and reduce the sluggish connection between muscle and bone.

    • If the muscles are more towards the muscle ends, Decrease the Damping parameter in the Muscle Ends tab of Muscle Constraint Properties Vellum SOP.

  3. Increase the Velocity Blend parameter in the Velocity Blend tab of Muscle Constraint Properties Vellum SOP. This should be your last resort after trying the other steps.

Muscles & Tissue

基本

Musclesの扱い方

Musclesレシピ

レガシーMuscles(Vellum Solver)