1# What is the Intersection Solver?

The Intersection Solver is a tool for detecting, visualizing, and fixing intersections between a deformable and a template or shape. If an imported deformable has modeling issues, you can effectively detect and fix them. Even if your imported deformable has no unintended intersections, Popul8’s fitting process may introduce minor intersections, especially when the shape differs significantly from the template. The Intersection Solver helps you address these scenarios effectively.

Creating an Intersection Solver

To create an Intersection Solver, right-click on the deformable, select Create, and then choose Intersection Solver. This will add an object as a child of the deformable. Each deformable can have only one instance of the tool. To delete it, right-click on the instance and select Delete.

Detecting intersections

To detect intersections, click the Verify button. Once the verification is complete, any detected intersections will be listed under Intersection Groups, with each group representing an independent intersection. You can merge nearby groups by adjusting the Merge Distance slider to set the minimum allowed distance between them, then clicking Verify again.

Visualizing intersections

Toggle Highlight all groups to activate visual markers, assigning a different color to each intersection. Alternatively, browse the Intersection Groups list and click View to highlight and zoom in on a specific intersection.

Fixing intersections

Each intersection has two properties:

• Expansion – Determines how much the intersection area needs to be inflated to eliminate the intersection.
• Influence Radius – Controls the area around the intersection affected by the inflation, ensuring a smoother result.

We automatically suggest appropriate values for both properties, customized for each intersection. Each property has a corresponding slider per intersection.

To fix an intersection using the suggested values, browse the Intersection Groups and click Fix on the intended intersection. This will apply the recommended values and display the result in real time. If the intersection is not fully resolved, you can fine-tune the values using the sliders. Always click Fix to apply any changes made through the sliders.

You can fix all intersection groups simultaneously by clicking Fix All at the top. This will apply the fixes to each group using the values set on the sliders.

At any time, you can click Verify to re-evaluate the intersections after applying the fixes. Clicking the Revert button will undo all fixes made since the last time Verify was clicked.

Limitations

Intersection groups that are close together but located on areas with opposite curvature—such as one group on each side of the armpit or one at the inner top part of each thigh—are challenging for our system to solve. Be especially cautious with these cases. We're working on improvements for these use cases, so stay tuned!

Saving and discarding fixes

Once you're satisfied with the intersection fixes, click Apply Changes to permanently accept them. After doing so, no further changes to the Asset Fitter will be allowed. If you wish to undo all fixes and start over, click Reset. This will also re-enable the usage of the Asset Fitter.

Interaction with the Asset Fitter

If you apply the Intersection Solver to a deformable with an associated Asset Fitter, the fitter will be applied first, followed by the solver. For example, if you’ve added stiffness to the deformable using the fitter, the solver will work on that modified version.

Once you save the intersection fixes, you will no longer be able to modify the deformable’s fitting—meaning you cannot add new stiffness regions, only the previously defined ones will remain.

If you wish to edit the deformable’s fitting further (e.g., add more stiffness regions), you must revert all intersection fixes by clicking Reset in the Intersection Solver. This will unlock the Asset Fitter, allowing you to make changes. You can then reapply the solver to the updated deformable.