Running Obi Cloth In Edit Mode

[josemendez]

Turns out collisions and a few other bits weren't really ready for in-editor simulation. In addition to extending ObiUpdater, you will need to make a few changes:

- Add [ExecuteInEditMode] to BurstColliderWorld.cs/OniColliderWorld.cs. This will allow collision data structures to be initialized in-editor.
- Add [ExecuteInEditMode] to ObiParticleAttachment.cs. This will allow attachments to run in edit mode.
- Comment out lines 1106-1126 of ObiActor.cs. These are intended to override renderable particle positions at edit time, to allow particle positions to reflect changes to the actor's transform in absence of simulation.
- Line 146 of ObiClothRendererBase.cs, remove  "Application.isPlaying" from the if() statement. This was intended to reduce work done in-editor.

With these changes, you can then use this ObiUpdater subclass to step the simulation forward in editor by clicking the inspector's "update" button.

Code:

using UnityEngine;

namespace Obi
{
    /// <summary>
    /// Updater class that will perform simulation at edit time.

    [AddComponentMenu("Physics/Obi/Obi Editor Updater", 801)]
    [ExecuteInEditMode]
    public class ObiEditorUpdater : ObiUpdater
    {

        /// <summary>
        /// Each FixedUpdate() call will be divided into several substeps. Performing more substeps will greatly improve the accuracy/convergence speed of the simulation.
        /// Increasing the amount of substeps is more effective than increasing the amount of constraint iterations.
        /// </summary>
        [Tooltip("Amount of substeps performed per FixedUpdate. Increasing the amount of substeps greatly improves accuracy and convergence speed.")]
        public int substeps = 1;

        [InspectorButton("UpdateEditor")]
        public bool update;

        private void OnValidate()
        {
            substeps = Mathf.Max(1, substeps);
        }

        private void UpdateEditor()
        {
            Step(0.02f);
        }

        private void Step(float timestep)
        {
            ObiProfiler.EnableProfiler();

            BeginStep(timestep);

            float substepDelta = timestep / (float)substeps;

            // Divide the step into multiple smaller substeps:
            for (int i = 0; i < substeps; ++i)
            {
                // Simulate Obi:
                Substep(substepDelta);
            }

            EndStep(substepDelta);

            Interpolate(timestep, timestep);

            ObiProfiler.DisableProfiler();
        }
    }
}

If you describe your use case more accurately, I can come up with better solutions for it after Christmas. Potential improvements include writing an in-editor fixed timestep loop to circumvent the absence of FixedUpdate() calls, supporting simulation reset, updating Unity's rigidbody physics in sync, and some others.

cheers!