o3de/Gems/NvCloth/Code/Source/Components/ClothComponentMesh/ActorClothSkinning.h

/*
 * Copyright (c) Contributors to the Open 3D Engine Project.
 * For complete copyright and license terms please see the LICENSE at the root of this distribution.
 *
 * SPDX-License-Identifier: Apache-2.0 OR MIT
 *
 */

#pragma once

#include <AzCore/std/limits.h>
#include <AzCore/Component/Entity.h>

#include <NvCloth/Types.h>

#include <Components/ClothComponentMesh/ClothComponentMesh.h>

namespace NvCloth
{
    //! One skinning influence of a vertex.
    struct SkinningInfluence
    {
        //! Weight of the joint that influences the vertex.
        float m_jointWeight = 0.0f;

        //! Index of the joint that influences the vertex.
        AZ::u16 m_jointIndex = AZStd::numeric_limits<AZ::u16>::max();
    };

    //! Class to retrieve skinning information from an actor on the same entity
    //! and use that data to apply skinning to vertices.
    class ActorClothSkinning
    {
    public:
        AZ_TYPE_INFO(ActorClothSkinning, "{3E7C664D-096B-4126-8553-3241BA965533}");

        virtual ~ActorClothSkinning() = default;

        static AZStd::unique_ptr<ActorClothSkinning> Create(
            AZ::EntityId entityId, 
            const MeshNodeInfo& meshNodeInfo,
            const AZStd::vector<SimParticleFormat>& originalMeshParticles,
            const size_t numSimulatedVertices,
            const AZStd::vector<int>& meshRemappedVertices);

        explicit ActorClothSkinning(AZ::EntityId entityId);

        //! Updates skinning with the current pose of the actor.
        virtual void UpdateSkinning() = 0;

        //! Applies skinning to a list of positions.
        //! @note w components are not affected.
        virtual void ApplySkinning(
            const AZStd::vector<AZ::Vector4>& originalPositions, 
            AZStd::vector<AZ::Vector4>& positions) = 0;

        //! Applies skinning to a list of positions and vectors whose vertices
        //! have not been used for simulation.
        virtual void ApplySkinningOnNonSimulatedVertices(
            const MeshClothInfo& originalData,
            ClothComponentMesh::RenderData& renderData) = 0;

        //! Updates visibility variables.
        void UpdateActorVisibility();

        //! Returns true if actor is currently visible on screen.
        bool IsActorVisible() const;

        //! Returns true if actor was visible on screen in previous update.
        bool WasActorVisible() const;

    protected:
        AZ::EntityId m_entityId;

        // Skinning influences of all vertices
        AZStd::vector<SkinningInfluence> m_skinningInfluences;

        struct SimulatedVertex
        {
            AZ::u32 m_influenceOffset = 0;
            // Influence count is a bit redundant since that is uniform across a sub-mesh,
            // not unique to each vertex. However, it is necessary to track it here,
            // since m_simulatedVertices remapped out of the original vertex order,
            // and there is no way to correlate an element of m_simulatedVertices to which
            // sub-mesh it came from
            AZ::u32 m_influenceCount = 0;
        };
        // Offsets to skinning influences that are part of the simulation
        AZStd::vector<SimulatedVertex> m_simulatedVertices;

        struct NonSimulatedVertex
        {
            AZ::u32 m_originalVertexIndex = 0;
            AZ::u32 m_influenceOffset = 0;
            // Influence count is a bit redundant since that is uniform across a sub-mesh,
            // not unique to each vertex. However, the code is simpler and less error
            // prone to just track the influence count here instead of associating a range
            // of non-simulated vertices to a particular sub-mesh
            AZ::u32 m_influenceCount = 0;
        };
        // Offsets to skinning influences that are not part of the simulation
        AZStd::vector<NonSimulatedVertex> m_nonSimulatedVertices;

        // Collection of skeleton joint indices that influence the vertices
        AZStd::vector<AZ::u16> m_jointIndices;

        // Visibility variables
        bool m_wasActorVisible = false;
        bool m_isActorVisible = false;
    };
}// namespace NvCloth