GetTrianglesContext.h

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// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
// SPDX-FileCopyrightText: 2021 Jorrit Rouwe
// SPDX-License-Identifier: MIT
 
#pragma once
 
#include <Jolt/Physics/Collision/Shape/Shape.h>
 
JPH_NAMESPACE_BEGIN
 
class PhysicsMaterial;
 
class GetTrianglesContextVertexList
{
public:
                    GetTrianglesContextVertexList(Vec3Arg inPositionCOM, QuatArg inRotation, Vec3Arg inScale, Mat44Arg inLocalTransform, const Vec3 *inTriangleVertices, size_t inNumTriangleVertices, const PhysicsMaterial *inMaterial) :
        mLocalToWorld(Mat44::sRotationTranslation(inRotation, inPositionCOM) * Mat44::sScale(inScale) * inLocalTransform),
        mTriangleVertices(inTriangleVertices),
        mNumTriangleVertices(inNumTriangleVertices),
        mMaterial(inMaterial),
        mIsInsideOut(ScaleHelpers::IsInsideOut(inScale))
    {
        static_assert(sizeof(GetTrianglesContextVertexList) <= sizeof(Shape::GetTrianglesContext), "GetTrianglesContext too small");
        JPH_ASSERT(IsAligned(this, alignof(GetTrianglesContextVertexList)));
        JPH_ASSERT(inNumTriangleVertices % 3 == 0);
    }
 
    int             GetTrianglesNext(int inMaxTrianglesRequested, Float3 *outTriangleVertices, const PhysicsMaterial **outMaterials)
    {
        JPH_ASSERT(inMaxTrianglesRequested >= Shape::cGetTrianglesMinTrianglesRequested);
 
        int total_num_vertices = min(inMaxTrianglesRequested * 3, int(mNumTriangleVertices - mCurrentVertex));
 
        if (mIsInsideOut)
        {
            // Store triangles flipped
            for (const Vec3 *v = mTriangleVertices + mCurrentVertex, *v_end = v + total_num_vertices; v < v_end; v += 3)
            {
                (mLocalToWorld * v[0]).StoreFloat3(outTriangleVertices++);
                (mLocalToWorld * v[2]).StoreFloat3(outTriangleVertices++);
                (mLocalToWorld * v[1]).StoreFloat3(outTriangleVertices++);
            }
        }
        else
        {
            // Store triangles
            for (const Vec3 *v = mTriangleVertices + mCurrentVertex, *v_end = v + total_num_vertices; v < v_end; v += 3)
            {
                (mLocalToWorld * v[0]).StoreFloat3(outTriangleVertices++);
                (mLocalToWorld * v[1]).StoreFloat3(outTriangleVertices++);
                (mLocalToWorld * v[2]).StoreFloat3(outTriangleVertices++);
            }
        }
 
        // Update the current vertex to point to the next vertex to get
        mCurrentVertex += total_num_vertices;
        int total_num_triangles = total_num_vertices / 3;
 
        // Store materials
        if (outMaterials != nullptr)
            for (const PhysicsMaterial **m = outMaterials, **m_end = outMaterials + total_num_triangles; m < m_end; ++m)
                *m = mMaterial;
 
        return total_num_triangles;
    }
 
    static void     sCreateHalfUnitSphereTop(std::vector<Vec3> &ioVertices, int inDetailLevel)
    {
        sCreateUnitSphereHelper(ioVertices,  Vec3::sAxisX(),  Vec3::sAxisY(),  Vec3::sAxisZ(), inDetailLevel);
        sCreateUnitSphereHelper(ioVertices,  Vec3::sAxisY(), -Vec3::sAxisX(),  Vec3::sAxisZ(), inDetailLevel);
        sCreateUnitSphereHelper(ioVertices,  Vec3::sAxisY(),  Vec3::sAxisX(), -Vec3::sAxisZ(), inDetailLevel);
        sCreateUnitSphereHelper(ioVertices, -Vec3::sAxisX(),  Vec3::sAxisY(), -Vec3::sAxisZ(), inDetailLevel);
    }
 
    static void     sCreateHalfUnitSphereBottom(std::vector<Vec3> &ioVertices, int inDetailLevel)
    {
        sCreateUnitSphereHelper(ioVertices, -Vec3::sAxisX(), -Vec3::sAxisY(),  Vec3::sAxisZ(), inDetailLevel);
        sCreateUnitSphereHelper(ioVertices, -Vec3::sAxisY(),  Vec3::sAxisX(),  Vec3::sAxisZ(), inDetailLevel);
        sCreateUnitSphereHelper(ioVertices,  Vec3::sAxisX(), -Vec3::sAxisY(), -Vec3::sAxisZ(), inDetailLevel);
        sCreateUnitSphereHelper(ioVertices, -Vec3::sAxisY(), -Vec3::sAxisX(), -Vec3::sAxisZ(), inDetailLevel);
    }
 
    static void     sCreateUnitOpenCylinder(std::vector<Vec3> &ioVertices, int inDetailLevel)
    {
        const Vec3 bottom_offset(0.0f, -2.0f, 0.0f);
        int num_verts = 4 * (1 << inDetailLevel);
        for (int i = 0; i < num_verts; ++i)
        {
            float angle1 = 2.0f * JPH_PI * (float(i) / num_verts);
            float angle2 = 2.0f * JPH_PI * (float(i + 1) / num_verts);
 
            Vec3 t1(Sin(angle1), 1.0f, Cos(angle1));
            Vec3 t2(Sin(angle2), 1.0f, Cos(angle2));
            Vec3 b1 = t1 + bottom_offset;
            Vec3 b2 = t2 + bottom_offset;
 
            ioVertices.push_back(t1);
            ioVertices.push_back(b1);
            ioVertices.push_back(t2);
 
            ioVertices.push_back(t2);
            ioVertices.push_back(b1);
            ioVertices.push_back(b2);
        }
    }
 
private:
    static void     sCreateUnitSphereHelper(std::vector<Vec3> &ioVertices, Vec3Arg inV1, Vec3Arg inV2, Vec3Arg inV3, int inLevel)
    {
        Vec3 center1 = (inV1 + inV2).Normalized();
        Vec3 center2 = (inV2 + inV3).Normalized();
        Vec3 center3 = (inV3 + inV1).Normalized();
 
        if (inLevel > 0)
        {
            int new_level = inLevel - 1;
            sCreateUnitSphereHelper(ioVertices, inV1, center1, center3, new_level);
            sCreateUnitSphereHelper(ioVertices, center1, center2, center3, new_level);
            sCreateUnitSphereHelper(ioVertices, center1, inV2, center2, new_level);
            sCreateUnitSphereHelper(ioVertices, center3, center2, inV3, new_level);
        }
        else
        {
            ioVertices.push_back(inV1);
            ioVertices.push_back(inV2);
            ioVertices.push_back(inV3);
        }
    }
 
    Mat44                   mLocalToWorld;
    const Vec3 *            mTriangleVertices;
    size_t                  mNumTriangleVertices;
    size_t                  mCurrentVertex = 0;
    const PhysicsMaterial * mMaterial;
    bool                    mIsInsideOut;
};
 
class GetTrianglesContextMultiVertexList
{
public:
                    GetTrianglesContextMultiVertexList(bool inIsInsideOut, const PhysicsMaterial *inMaterial) :
        mMaterial(inMaterial),
        mIsInsideOut(inIsInsideOut)
    {
        static_assert(sizeof(GetTrianglesContextMultiVertexList) <= sizeof(Shape::GetTrianglesContext), "GetTrianglesContext too small");
        JPH_ASSERT(IsAligned(this, alignof(GetTrianglesContextMultiVertexList)));
    }
 
    void            AddPart(Mat44Arg inLocalToWorld, const Vec3 *inTriangleVertices, size_t inNumTriangleVertices)
    {
        JPH_ASSERT(inNumTriangleVertices % 3 == 0);
 
        mParts.push_back({ inLocalToWorld, inTriangleVertices, inNumTriangleVertices });
    }
 
    int             GetTrianglesNext(int inMaxTrianglesRequested, Float3 *outTriangleVertices, const PhysicsMaterial **outMaterials)
    {
        JPH_ASSERT(inMaxTrianglesRequested >= Shape::cGetTrianglesMinTrianglesRequested);
 
        int total_num_vertices = 0;
        int max_vertices_requested = inMaxTrianglesRequested * 3;
 
        // Loop over parts
        for (; mCurrentPart < mParts.size(); ++mCurrentPart)
        {
            const Part &part = mParts[mCurrentPart];
 
            // Calculate how many vertices to take from this part
            int part_num_vertices = min(max_vertices_requested, int(part.mNumTriangleVertices - mCurrentVertex));
            if (part_num_vertices == 0)
                break;
 
            max_vertices_requested -= part_num_vertices;
            total_num_vertices += part_num_vertices;
 
            if (mIsInsideOut)
            {
                // Store triangles flipped
                for (const Vec3 *v = part.mTriangleVertices + mCurrentVertex, *v_end = v + part_num_vertices; v < v_end; v += 3)
                {
                    (part.mLocalToWorld * v[0]).StoreFloat3(outTriangleVertices++);
                    (part.mLocalToWorld * v[2]).StoreFloat3(outTriangleVertices++);
                    (part.mLocalToWorld * v[1]).StoreFloat3(outTriangleVertices++);
                }
            }
            else
            {
                // Store triangles
                for (const Vec3 *v = part.mTriangleVertices + mCurrentVertex, *v_end = v + part_num_vertices; v < v_end; v += 3)
                {
                    (part.mLocalToWorld * v[0]).StoreFloat3(outTriangleVertices++);
                    (part.mLocalToWorld * v[1]).StoreFloat3(outTriangleVertices++);
                    (part.mLocalToWorld * v[2]).StoreFloat3(outTriangleVertices++);
                }
            }
 
            // Update the current vertex to point to the next vertex to get
            mCurrentVertex += part_num_vertices;
 
            // Check if we completed this part
            if (mCurrentVertex < part.mNumTriangleVertices)
                break;
 
            // Reset current vertex for the next part
            mCurrentVertex = 0;
        }
 
        int total_num_triangles = total_num_vertices / 3;
 
        // Store materials
        if (outMaterials != nullptr)
            for (const PhysicsMaterial **m = outMaterials, **m_end = outMaterials + total_num_triangles; m < m_end; ++m)
                *m = mMaterial;
 
        return total_num_triangles;
    }
 
private:
    struct Part
    {
        Mat44               mLocalToWorld;
        const Vec3 *        mTriangleVertices;
        size_t              mNumTriangleVertices;
    };
 
    StaticArray<Part, 3>    mParts;
    uint                    mCurrentPart = 0;
    size_t                  mCurrentVertex = 0;
    const PhysicsMaterial * mMaterial;
    bool                    mIsInsideOut;
};
 
JPH_NAMESPACE_END