InternalEdgeRemovingCollector.h

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// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
// SPDX-FileCopyrightText: 2024 Jorrit Rouwe
// SPDX-License-Identifier: MIT
 
#pragma once
 
#include <Jolt/Core/QuickSort.h>
#include <Jolt/Physics/Collision/CollisionDispatch.h>
 
//#define JPH_INTERNAL_EDGE_REMOVING_COLLECTOR_DEBUG
 
#ifdef JPH_INTERNAL_EDGE_REMOVING_COLLECTOR_DEBUG
#include <Jolt/Renderer/DebugRenderer.h>
#endif // JPH_INTERNAL_EDGE_REMOVING_COLLECTOR_DEBUG
 
JPH_NAMESPACE_BEGIN
 
class InternalEdgeRemovingCollector : public CollideShapeCollector
{
    static constexpr uint cMaxDelayedResults = 16;
    static constexpr uint cMaxVoidedFeatures = 128;
 
    inline bool             IsVoided(const SubShapeID &inSubShapeID, Vec3 inV) const
    {
        for (const Voided &vf : mVoidedFeatures)
            if (vf.mSubShapeID == inSubShapeID
                && inV.IsClose(Vec3::sLoadFloat3Unsafe(vf.mFeature), 1.0e-8f))
                return true;
        return false;
    }
 
    inline void             VoidFeatures(const CollideShapeResult &inResult)
    {
        if (mVoidedFeatures.size() < cMaxVoidedFeatures)
            for (const Vec3 &v : inResult.mShape2Face)
                if (!IsVoided(inResult.mSubShapeID1, v))
                {
                    Voided vf;
                    v.StoreFloat3(&vf.mFeature);
                    vf.mSubShapeID = inResult.mSubShapeID1;
                    mVoidedFeatures.push_back(vf);
                    if (mVoidedFeatures.size() == cMaxVoidedFeatures)
                        break;
                }
    }
 
    inline void             Chain(const CollideShapeResult &inResult)
    {
        // Make sure the chained collector has the same context as we do
        mChainedCollector.SetContext(GetContext());
 
        // Forward the hit
        mChainedCollector.AddHit(inResult);
 
        // If our chained collector updated its early out fraction, we need to follow
        UpdateEarlyOutFraction(mChainedCollector.GetEarlyOutFraction());
    }
 
    inline void             ChainAndVoid(const CollideShapeResult &inResult)
    {
        Chain(inResult);
        VoidFeatures(inResult);
 
    #ifdef JPH_INTERNAL_EDGE_REMOVING_COLLECTOR_DEBUG
        DebugRenderer::sInstance->DrawWirePolygon(RMat44::sIdentity(), inResult.mShape2Face, Color::sGreen);
        DebugRenderer::sInstance->DrawArrow(RVec3(inResult.mContactPointOn2), RVec3(inResult.mContactPointOn2) + inResult.mPenetrationAxis.NormalizedOr(Vec3::sZero()), Color::sGreen, 0.1f);
    #endif // JPH_INTERNAL_EDGE_REMOVING_COLLECTOR_DEBUG
    }
 
public:
    explicit                InternalEdgeRemovingCollector(CollideShapeCollector &inChainedCollector) :
        mChainedCollector(inChainedCollector)
    {
    }
 
    // See: CollideShapeCollector::Reset
    virtual void            Reset() override
    {
        CollideShapeCollector::Reset();
 
        mChainedCollector.Reset();
 
        mVoidedFeatures.clear();
        mDelayedResults.clear();
    }
 
    // See: CollideShapeCollector::OnBody
    virtual void            OnBody(const Body &inBody) override
    {
        // Just forward the call to our chained collector
        mChainedCollector.OnBody(inBody);
    }
 
    // See: CollideShapeCollector::AddHit
    virtual void            AddHit(const CollideShapeResult &inResult) override
    {
        // We only support welding when the shape is a triangle or has more vertices so that we can calculate a normal
        if (inResult.mShape2Face.size() < 3)
            return ChainAndVoid(inResult);
 
        // Get the triangle normal of shape 2 face
        Vec3 triangle_normal = (inResult.mShape2Face[1] - inResult.mShape2Face[0]).Cross(inResult.mShape2Face[2] - inResult.mShape2Face[0]);
        float triangle_normal_len = triangle_normal.Length();
        if (triangle_normal_len < 1e-6f)
            return ChainAndVoid(inResult);
 
        // If the triangle normal matches the contact normal within 1 degree, we can process the contact immediately
        // We make the assumption here that if the contact normal and the triangle normal align that the we're dealing with a 'face contact'
        Vec3 contact_normal = -inResult.mPenetrationAxis;
        float contact_normal_len = inResult.mPenetrationAxis.Length();
        if (triangle_normal.Dot(contact_normal) > 0.999848f * contact_normal_len * triangle_normal_len) // cos(1 degree)
            return ChainAndVoid(inResult);
 
        // Delayed processing
        if (mDelayedResults.size() == cMaxDelayedResults)
            return ChainAndVoid(inResult);
        mDelayedResults.push_back(inResult);
    }
 
    void                    Flush()
    {
        // Sort on biggest penetration depth first
        uint sorted_indices[cMaxDelayedResults];
        for (uint i = 0; i < uint(mDelayedResults.size()); ++i)
            sorted_indices[i] = i;
        QuickSort(sorted_indices, sorted_indices + mDelayedResults.size(), [this](uint inLHS, uint inRHS) { return mDelayedResults[inLHS].mPenetrationDepth > mDelayedResults[inRHS].mPenetrationDepth; });
 
        // Loop over all results
        for (uint i = 0; i < uint(mDelayedResults.size()); ++i)
        {
            const CollideShapeResult &r = mDelayedResults[sorted_indices[i]];
 
            // Determine which vertex or which edge is the closest to the contact point
            float best_dist_sq = FLT_MAX;
            uint best_v1_idx = 0;
            uint best_v2_idx = 0;
            uint num_v = uint(r.mShape2Face.size());
            uint v1_idx = num_v - 1;
            Vec3 v1 = r.mShape2Face[v1_idx] - r.mContactPointOn2;
            for (uint v2_idx = 0; v2_idx < num_v; ++v2_idx)
            {
                Vec3 v2 = r.mShape2Face[v2_idx] - r.mContactPointOn2;
                Vec3 v1_v2 = v2 - v1;
                float denominator = v1_v2.LengthSq();
                if (denominator < Square(FLT_EPSILON))
                {
                    // Degenerate, assume v1 is closest, v2 will be tested in a later iteration
                    float v1_len_sq = v1.LengthSq();
                    if (v1_len_sq < best_dist_sq)
                    {
                        best_dist_sq = v1_len_sq;
                        best_v1_idx = v1_idx;
                        best_v2_idx = v1_idx;
                    }
                }
                else
                {
                    // Taken from ClosestPoint::GetBaryCentricCoordinates
                    float fraction = -v1.Dot(v1_v2) / denominator;
                    if (fraction < 1.0e-6f)
                    {
                        // Closest lies on v1
                        float v1_len_sq = v1.LengthSq();
                        if (v1_len_sq < best_dist_sq)
                        {
                            best_dist_sq = v1_len_sq;
                            best_v1_idx = v1_idx;
                            best_v2_idx = v1_idx;
                        }
                    }
                    else if (fraction < 1.0f - 1.0e-6f)
                    {
                        // Closest lies on the line segment v1, v2
                        Vec3 closest = v1 + fraction * v1_v2;
                        float closest_len_sq = closest.LengthSq();
                        if (closest_len_sq < best_dist_sq)
                        {
                            best_dist_sq = closest_len_sq;
                            best_v1_idx = v1_idx;
                            best_v2_idx = v2_idx;
                        }
                    }
                    // else closest is v2, but v2 will be tested in a later iteration
                }
 
                v1_idx = v2_idx;
                v1 = v2;
            }
 
            // Check if this vertex/edge is voided
            bool voided = IsVoided(r.mSubShapeID1, r.mShape2Face[best_v1_idx])
                && (best_v1_idx == best_v2_idx || IsVoided(r.mSubShapeID1, r.mShape2Face[best_v2_idx]));
 
        #ifdef JPH_INTERNAL_EDGE_REMOVING_COLLECTOR_DEBUG
            Color color = voided? Color::sRed : Color::sYellow;
            DebugRenderer::sInstance->DrawText3D(RVec3(r.mContactPointOn2), StringFormat("%d: %g", i, r.mPenetrationDepth), color, 0.1f);
            DebugRenderer::sInstance->DrawWirePolygon(RMat44::sIdentity(), r.mShape2Face, color);
            DebugRenderer::sInstance->DrawArrow(RVec3(r.mContactPointOn2), RVec3(r.mContactPointOn2) + r.mPenetrationAxis.NormalizedOr(Vec3::sZero()), color, 0.1f);
            DebugRenderer::sInstance->DrawMarker(RVec3(r.mShape2Face[best_v1_idx]), IsVoided(r.mSubShapeID1, r.mShape2Face[best_v1_idx])? Color::sRed : Color::sYellow, 0.1f);
            DebugRenderer::sInstance->DrawMarker(RVec3(r.mShape2Face[best_v2_idx]), IsVoided(r.mSubShapeID1, r.mShape2Face[best_v2_idx])? Color::sRed : Color::sYellow, 0.1f);
        #endif // JPH_INTERNAL_EDGE_REMOVING_COLLECTOR_DEBUG
 
            // No voided features, accept the contact
            if (!voided)
                Chain(r);
 
            // Void the features of this face
            VoidFeatures(r);
        }
 
        // All delayed results have been processed
        mVoidedFeatures.clear();
        mDelayedResults.clear();
    }
 
    static void             sCollideShapeVsShape(const Shape *inShape1, const Shape *inShape2, Vec3Arg inScale1, Vec3Arg inScale2, Mat44Arg inCenterOfMassTransform1, Mat44Arg inCenterOfMassTransform2, const SubShapeIDCreator &inSubShapeIDCreator1, const SubShapeIDCreator &inSubShapeIDCreator2, const CollideShapeSettings &inCollideShapeSettings, CollideShapeCollector &ioCollector, const ShapeFilter &inShapeFilter = { })
    {
        JPH_ASSERT(inCollideShapeSettings.mCollectFacesMode == ECollectFacesMode::CollectFaces); // Won't work without collecting faces
 
        InternalEdgeRemovingCollector wrapper(ioCollector);
        CollisionDispatch::sCollideShapeVsShape(inShape1, inShape2, inScale1, inScale2, inCenterOfMassTransform1, inCenterOfMassTransform2, inSubShapeIDCreator1, inSubShapeIDCreator2, inCollideShapeSettings, wrapper, inShapeFilter);
        wrapper.Flush();
    }
 
private:
    // This algorithm tests a convex shape (shape 1) against a set of polygons (shape 2).
    // This assumption doesn't hold if the shape we're testing is a compound shape, so we must also
    // store the sub shape ID and ignore voided features that belong to another sub shape ID.
    struct Voided
    {
        Float3              mFeature;               // Feature that is voided (of shape 2). Read with Vec3::sLoadFloat3Unsafe so must not be the last member.
        SubShapeID          mSubShapeID;            // Sub shape ID of the shape that is colliding against the feature (of shape 1).
    };
 
    CollideShapeCollector & mChainedCollector;
    StaticArray<Voided, cMaxVoidedFeatures> mVoidedFeatures;
    StaticArray<CollideShapeResult, cMaxDelayedResults> mDelayedResults;
};
 
JPH_NAMESPACE_END