Performance When Working With Models in the SDK

Updated: 06/28/2024

Performance

Update rate

When displaying models on the SDK, performance may be degraded depending on the order in which ArtMeshes are drawn.
Cubism models are drawn one ArtMesh at a time from the back (canvas side).
As you draw an ArtMesh on the screen, if its blend mode differs from that of the ArtMesh drawn immediately before it, performance on the SDK will be degraded.
Settings where switching will degrade performance are as follows.

• Texture used by the ArtMesh to be drawn
• Blend mode (normal, additive, multiply) of the ArtMesh to be drawn
• Whether the ArtMesh to be drawn is clipped or not

These factors will affect each other.
Clipping switches settings even if the texture, blend mode, and ArtMesh that serves as the mask are the same.

For example, suppose a model with two textures and some ArtMeshes is placed in the following order from the back.

[Name]	[ID]	[Draw settings]	[Switchover occurs]
Right eyelash	ArtMesh6	Texture: 2nd sheet	○
Right eyebrow	ArtMesh7		○
Right cheek	ArtMesh8	Blend mode: Multiply	○
Right highlight	ArtMesh9	Clipping: Right white eye, blend mode: Additive	○
Right pupil	ArtMesh10	Clipping: Right white eye	○
Right white eye	ArtMesh11		○
Left eyelash	ArtMesh16	Texture: 2nd sheet	○
Left eyebrow	ArtMesh17	Blend mode: Multiply	○
Left cheek	ArtMesh18		○
Left highlight	ArtMesh19	Clipping: Left white eye, blend mode: Additive	○
Left pupil	ArtMesh20	Clipping: Left white eye	○
Left white eye	ArtMesh21

These ArtMeshes are drawn in order from the bottom of the table.
When lined up like this, the draw settings are counted from the bottom of the table and a changeover occurs eleven times.

If this draw order is rearranged as follows, the number of times the draw setting is switched is reduced to seven times.

[Name]	[ID]	[Draw settings]	[Switchover occurs]
Right eyebrow	ArtMesh6	Texture: 2nd sheet
Left eyebrow	ArtMesh16	Texture: 2nd sheet	○
Right cheek	ArtMesh7	Blend mode: Multiply
Left cheek	ArtMesh17	Blend mode: Multiply	○
Right eyelash	ArtMesh8
Left eyelash	ArtMesh18		○
Right highlight	ArtMesh9	Clipping: Right white eye, blend mode: Additive	○
Left highlight	ArtMesh19	Clipping: Left white eye, blend mode: Additive	○
Right pupil	ArtMesh10	Clipping: Right white eye	○
Left pupil	ArtMesh29	Clipping: Left white eye	○
Right white eye	ArtMesh11
Left white eye	ArtMesh21

The order and switching status of ArtMeshes can be checked in Cubism Viewer for OW.
If you set up a deformation in which the draw order changes depending on the parameters, it becomes difficult to predict the number of times it will switch.

Also, be careful not to use too many of the following objects or too many settings for each status, as it will affect performance of the SDK.

1. Number of ArtMeshes
2. Number of polygons
3. Number of deformers
4. Division number of deformer conversion
5. Number of deformer parent-child hierarchies
6. Number of parameters set for one object (ArtMesh, deformer)

Of these, number 6 has a particularly large impact, and it is typically recommended that up to two settings be used.
This is because the amount of blending computation between the keyforms of the parameters increases with multiplication.

Reference: Keyforms (Parent-Child Hierarchy Movement)

For example, if two parameters are set for one ArtMesh, a blend calculation is performed for each parameter, and then the results of each calculation are further blended together.
Therefore, the more parameters set, the more blending calculations are required.

When the number of parameter multiplications is large, you can greatly reduce the computational cost by replacing these multiplications with the Bend Shape function, which adds the differences to the model shape.

In addition, if the ArtMesh or deformer falls outside the range of the parent warp deformer, performance is reduced due to the increased processing load.
For more information on points to keep in mind when building parent-child hierarchies, see the Combination of Parent-Child Hierarchy page below.

Combination of Parent-Child Hierarchy

Initialization speed

Extended interpolation is a function that curvilinearly interpolates linear interpolation of parameters, and, in actuality, automatically generates a specified number of keyforms for extended interpolation between keyforms.
Therefore, when extended interpolation is set on an object with multiple parameters, the size of the model file increases proportionally because the keyforms added by extended interpolation are multiplied with each other.

Please note that when dealing with extended interpolation in the SDK, there is little effect on performance during execution, but there is a slowdown when loading the model.

Resolution

If the mesh of the mask occupies a large area of the displayed screen, the resolution of the mask on the screen will be reduced and fine expression may be lost.
This occurs when a mask created at a smaller size than its actual size is enlarged to a larger size, because the resolution of the texture that generates the mask does not change.

To avoid this, avoid using large masks.