StandardShapes.cpp

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/** @file   StandardShapes.cpp
 *  @brief  Implementation of the StandardShapes class
 *
 *  The primitive geometry data comes from
 *  http://geometrictools.com/Documentation/PlatonicSolids.pdf.
 */

#include <assimp/StandardShapes.h>
#include <assimp/StringComparison.h>
#include <assimp/mesh.h>

namespace Assimp {

#define ADD_TRIANGLE(n0, n1, n2) \
    positions.push_back(n0);     \
    positions.push_back(n1);     \
    positions.push_back(n2);

#define ADD_PENTAGON(n0, n1, n2, n3, n4) \
    if (polygons) {                      \
        positions.push_back(n0);         \
        positions.push_back(n1);         \
        positions.push_back(n2);         \
        positions.push_back(n3);         \
        positions.push_back(n4);         \
    } else {                             \
        ADD_TRIANGLE(n0, n1, n2)         \
        ADD_TRIANGLE(n0, n2, n3)         \
        ADD_TRIANGLE(n0, n3, n4)         \
    }

#define ADD_QUAD(n0, n1, n2, n3) \
    if (polygons) {              \
        positions.push_back(n0); \
        positions.push_back(n1); \
        positions.push_back(n2); \
        positions.push_back(n3); \
    } else {                     \
        ADD_TRIANGLE(n0, n1, n2) \
        ADD_TRIANGLE(n0, n2, n3) \
    }

// ------------------------------------------------------------------------------------------------
// Fast subdivision for a mesh whose verts have a magnitude of 1
void Subdivide(std::vector<aiVector3D> &positions) {
    // assume this to be constant - (fixme: must be 1.0? I think so)
    const ai_real fl1 = positions[0].Length();

    unsigned int origSize = (unsigned int)positions.size();
    for (unsigned int i = 0; i < origSize; i += 3) {
        aiVector3D &tv0 = positions[i];
        aiVector3D &tv1 = positions[i + 1];
        aiVector3D &tv2 = positions[i + 2];

        aiVector3D a = tv0, b = tv1, c = tv2;
        aiVector3D v1 = aiVector3D(a.x + b.x, a.y + b.y, a.z + b.z).Normalize() * fl1;
        aiVector3D v2 = aiVector3D(a.x + c.x, a.y + c.y, a.z + c.z).Normalize() * fl1;
        aiVector3D v3 = aiVector3D(b.x + c.x, b.y + c.y, b.z + c.z).Normalize() * fl1;

        tv0 = v1;
        tv1 = v3;
        tv2 = v2; // overwrite the original
        ADD_TRIANGLE(v1, v2, a);
        ADD_TRIANGLE(v2, v3, c);
        ADD_TRIANGLE(v3, v1, b);
    }
}

// ------------------------------------------------------------------------------------------------
// Construct a mesh from given vertex positions
aiMesh *StandardShapes::MakeMesh(const std::vector<aiVector3D> &positions,
        unsigned int numIndices) {
    if (positions.empty() || !numIndices) {
        return nullptr;
    }

    // Determine which kinds of primitives the mesh consists of
    aiMesh *out = new aiMesh();
    switch (numIndices) {
    case 1:
        out->mPrimitiveTypes = aiPrimitiveType_POINT;
        break;
    case 2:
        out->mPrimitiveTypes = aiPrimitiveType_LINE;
        break;
    case 3:
        out->mPrimitiveTypes = aiPrimitiveType_TRIANGLE;
        break;
    default:
        out->mPrimitiveTypes = aiPrimitiveType_POLYGON;
        break;
    };

    out->mNumFaces = (unsigned int)positions.size() / numIndices;
    out->mFaces = new aiFace[out->mNumFaces];
    for (unsigned int i = 0, a = 0; i < out->mNumFaces; ++i) {
        aiFace &f = out->mFaces[i];
        f.mNumIndices = numIndices;
        f.mIndices = new unsigned int[numIndices];
        for (unsigned int j = 0; j < numIndices; ++j, ++a) {
            f.mIndices[j] = a;
        }
    }
    out->mNumVertices = (unsigned int)positions.size();
    out->mVertices = new aiVector3D[out->mNumVertices];
    ::memcpy(out->mVertices, &positions[0], out->mNumVertices * sizeof(aiVector3D));

    return out;
}

// ------------------------------------------------------------------------------------------------
// Construct a mesh with a specific shape (callback)
aiMesh *StandardShapes::MakeMesh(unsigned int (*GenerateFunc)(
        std::vector<aiVector3D> &)) {
    std::vector<aiVector3D> temp;
    unsigned num = (*GenerateFunc)(temp);
    return MakeMesh(temp, num);
}

// ------------------------------------------------------------------------------------------------
// Construct a mesh with a specific shape (callback)
aiMesh *StandardShapes::MakeMesh(unsigned int (*GenerateFunc)(
        std::vector<aiVector3D> &, bool)) {
    std::vector<aiVector3D> temp;
    unsigned num = (*GenerateFunc)(temp, true);
    return MakeMesh(temp, num);
}

// ------------------------------------------------------------------------------------------------
// Construct a mesh with a specific shape (callback)
aiMesh *StandardShapes::MakeMesh(unsigned int num, void (*GenerateFunc)(
                                                           unsigned int, std::vector<aiVector3D> &)) {
    std::vector<aiVector3D> temp;
    (*GenerateFunc)(num, temp);
    return MakeMesh(temp, 3);
}

// ------------------------------------------------------------------------------------------------
// Build an incosahedron with points.magnitude == 1
unsigned int StandardShapes::MakeIcosahedron(std::vector<aiVector3D> &positions) {
    positions.reserve(positions.size() + 60);

    const ai_real t = (ai_real(1.0) + ai_real(2.236067977)) / ai_real(2.0);
    const ai_real s = std::sqrt(ai_real(1.0) + t * t);

    const aiVector3D v0 = aiVector3D(t, 1.0, 0.0) / s;
    const aiVector3D v1 = aiVector3D(-t, 1.0, 0.0) / s;
    const aiVector3D v2 = aiVector3D(t, -1.0, 0.0) / s;
    const aiVector3D v3 = aiVector3D(-t, -1.0, 0.0) / s;
    const aiVector3D v4 = aiVector3D(1.0, 0.0, t) / s;
    const aiVector3D v5 = aiVector3D(1.0, 0.0, -t) / s;
    const aiVector3D v6 = aiVector3D(-1.0, 0.0, t) / s;
    const aiVector3D v7 = aiVector3D(-1.0, 0.0, -t) / s;
    const aiVector3D v8 = aiVector3D(0.0, t, 1.0) / s;
    const aiVector3D v9 = aiVector3D(0.0, -t, 1.0) / s;
    const aiVector3D v10 = aiVector3D(0.0, t, -1.0) / s;
    const aiVector3D v11 = aiVector3D(0.0, -t, -1.0) / s;

    ADD_TRIANGLE(v0, v8, v4);
    ADD_TRIANGLE(v0, v5, v10);
    ADD_TRIANGLE(v2, v4, v9);
    ADD_TRIANGLE(v2, v11, v5);

    ADD_TRIANGLE(v1, v6, v8);
    ADD_TRIANGLE(v1, v10, v7);
    ADD_TRIANGLE(v3, v9, v6);
    ADD_TRIANGLE(v3, v7, v11);

    ADD_TRIANGLE(v0, v10, v8);
    ADD_TRIANGLE(v1, v8, v10);
    ADD_TRIANGLE(v2, v9, v11);
    ADD_TRIANGLE(v3, v11, v9);

    ADD_TRIANGLE(v4, v2, v0);
    ADD_TRIANGLE(v5, v0, v2);
    ADD_TRIANGLE(v6, v1, v3);
    ADD_TRIANGLE(v7, v3, v1);

    ADD_TRIANGLE(v8, v6, v4);
    ADD_TRIANGLE(v9, v4, v6);
    ADD_TRIANGLE(v10, v5, v7);
    ADD_TRIANGLE(v11, v7, v5);
    return 3;
}

// ------------------------------------------------------------------------------------------------
// Build a dodecahedron with points.magnitude == 1
unsigned int StandardShapes::MakeDodecahedron(std::vector<aiVector3D> &positions,
        bool polygons /*= false*/) {
    positions.reserve(positions.size() + 108);

    const ai_real a = ai_real(1.0) / ai_real(1.7320508);
    const ai_real b = std::sqrt((ai_real(3.0) - ai_real(2.23606797)) / ai_real(6.0));
    const ai_real c = std::sqrt((ai_real(3.0) + ai_real(2.23606797f)) / ai_real(6.0));

    const aiVector3D v0 = aiVector3D(a, a, a);
    const aiVector3D v1 = aiVector3D(a, a, -a);
    const aiVector3D v2 = aiVector3D(a, -a, a);
    const aiVector3D v3 = aiVector3D(a, -a, -a);
    const aiVector3D v4 = aiVector3D(-a, a, a);
    const aiVector3D v5 = aiVector3D(-a, a, -a);
    const aiVector3D v6 = aiVector3D(-a, -a, a);
    const aiVector3D v7 = aiVector3D(-a, -a, -a);
    const aiVector3D v8 = aiVector3D(b, c, 0.0);
    const aiVector3D v9 = aiVector3D(-b, c, 0.0);
    const aiVector3D v10 = aiVector3D(b, -c, 0.0);
    const aiVector3D v11 = aiVector3D(-b, -c, 0.0);
    const aiVector3D v12 = aiVector3D(c, 0.0, b);
    const aiVector3D v13 = aiVector3D(c, 0.0, -b);
    const aiVector3D v14 = aiVector3D(-c, 0.0, b);
    const aiVector3D v15 = aiVector3D(-c, 0.0, -b);
    const aiVector3D v16 = aiVector3D(0.0, b, c);
    const aiVector3D v17 = aiVector3D(0.0, -b, c);
    const aiVector3D v18 = aiVector3D(0.0, b, -c);
    const aiVector3D v19 = aiVector3D(0.0, -b, -c);

    ADD_PENTAGON(v0, v8, v9, v4, v16);
    ADD_PENTAGON(v0, v12, v13, v1, v8);
    ADD_PENTAGON(v0, v16, v17, v2, v12);
    ADD_PENTAGON(v8, v1, v18, v5, v9);
    ADD_PENTAGON(v12, v2, v10, v3, v13);
    ADD_PENTAGON(v16, v4, v14, v6, v17);
    ADD_PENTAGON(v9, v5, v15, v14, v4);

    ADD_PENTAGON(v6, v11, v10, v2, v17);
    ADD_PENTAGON(v3, v19, v18, v1, v13);
    ADD_PENTAGON(v7, v15, v5, v18, v19);
    ADD_PENTAGON(v7, v11, v6, v14, v15);
    ADD_PENTAGON(v7, v19, v3, v10, v11);
    return (polygons ? 5 : 3);
}

// ------------------------------------------------------------------------------------------------
// Build an octahedron with points.magnitude == 1
unsigned int StandardShapes::MakeOctahedron(std::vector<aiVector3D> &positions) {
    positions.reserve(positions.size() + 24);

    const aiVector3D v0 = aiVector3D(1.0, 0.0, 0.0);
    const aiVector3D v1 = aiVector3D(-1.0, 0.0, 0.0);
    const aiVector3D v2 = aiVector3D(0.0, 1.0, 0.0);
    const aiVector3D v3 = aiVector3D(0.0, -1.0, 0.0);
    const aiVector3D v4 = aiVector3D(0.0, 0.0, 1.0);
    const aiVector3D v5 = aiVector3D(0.0, 0.0, -1.0);

    ADD_TRIANGLE(v4, v0, v2);
    ADD_TRIANGLE(v4, v2, v1);
    ADD_TRIANGLE(v4, v1, v3);
    ADD_TRIANGLE(v4, v3, v0);

    ADD_TRIANGLE(v5, v2, v0);
    ADD_TRIANGLE(v5, v1, v2);
    ADD_TRIANGLE(v5, v3, v1);
    ADD_TRIANGLE(v5, v0, v3);
    return 3;
}

// ------------------------------------------------------------------------------------------------
// Build a tetrahedron with points.magnitude == 1
unsigned int StandardShapes::MakeTetrahedron(std::vector<aiVector3D> &positions) {
    positions.reserve(positions.size() + 9);

    const ai_real invThree = ai_real(1.0) / ai_real(3.0);
    const ai_real a = ai_real(1.41421) * invThree;
    const ai_real b = ai_real(2.4494) * invThree;

    const aiVector3D v0 = aiVector3D(0.0, 0.0, 1.0);
    const aiVector3D v1 = aiVector3D(2 * a, 0, -invThree);
    const aiVector3D v2 = aiVector3D(-a, b, -invThree);
    const aiVector3D v3 = aiVector3D(-a, -b, -invThree);

    ADD_TRIANGLE(v0, v1, v2);
    ADD_TRIANGLE(v0, v2, v3);
    ADD_TRIANGLE(v0, v3, v1);
    ADD_TRIANGLE(v1, v3, v2);
    return 3;
}

// ------------------------------------------------------------------------------------------------
// Build a hexahedron with points.magnitude == 1
unsigned int StandardShapes::MakeHexahedron(std::vector<aiVector3D> &positions,
        bool polygons /*= false*/) {
    positions.reserve(positions.size() + 36);
    const ai_real length = ai_real(1.0) / ai_real(1.73205080);

    const aiVector3D v0 = aiVector3D(-1.0, -1.0, -1.0) * length;
    const aiVector3D v1 = aiVector3D(1.0, -1.0, -1.0) * length;
    const aiVector3D v2 = aiVector3D(1.0, 1.0, -1.0) * length;
    const aiVector3D v3 = aiVector3D(-1.0, 1.0, -1.0) * length;
    const aiVector3D v4 = aiVector3D(-1.0, -1.0, 1.0) * length;
    const aiVector3D v5 = aiVector3D(1.0, -1.0, 1.0) * length;
    const aiVector3D v6 = aiVector3D(1.0, 1.0, 1.0) * length;
    const aiVector3D v7 = aiVector3D(-1.0, 1.0, 1.0) * length;

    ADD_QUAD(v0, v3, v2, v1);
    ADD_QUAD(v0, v1, v5, v4);
    ADD_QUAD(v0, v4, v7, v3);
    ADD_QUAD(v6, v5, v1, v2);
    ADD_QUAD(v6, v2, v3, v7);
    ADD_QUAD(v6, v7, v4, v5);
    return (polygons ? 4 : 3);
}

// Cleanup ...
#undef ADD_TRIANGLE
#undef ADD_QUAD
#undef ADD_PENTAGON

// ------------------------------------------------------------------------------------------------
// Create a subdivision sphere
void StandardShapes::MakeSphere(unsigned int tess,
        std::vector<aiVector3D> &positions) {
    // Reserve enough storage. Every subdivision
    // splits each triangle in 4, the icosahedron consists of 60 verts
    positions.reserve(positions.size() + 60 * integer_pow(4, tess));

    // Construct an icosahedron to start with
    MakeIcosahedron(positions);

    // ... and subdivide it until the requested output
    // tessellation is reached
    for (unsigned int i = 0; i < tess; ++i)
        Subdivide(positions);
}

// ------------------------------------------------------------------------------------------------
// Build a cone
void StandardShapes::MakeCone(ai_real height, ai_real radius1,
        ai_real radius2, unsigned int tess,
        std::vector<aiVector3D> &positions, bool bOpen /*= false */) {
    // Sorry, a cone with less than 3 segments makes ABSOLUTELY NO SENSE
    if (tess < 3 || !height)
        return;

    size_t old = positions.size();

    // No negative radii
    radius1 = std::fabs(radius1);
    radius2 = std::fabs(radius2);

    ai_real halfHeight = height / ai_real(2.0);

    // radius1 is always the smaller one
    if (radius2 > radius1) {
        std::swap(radius2, radius1);
        halfHeight = -halfHeight;
    } else
        old = SIZE_MAX;

    // Use a large epsilon to check whether the cone is pointy
    if (radius1 < (radius2 - radius1) * 10e-3) radius1 = 0.0;

    // We will need 3*2 verts per segment + 3*2 verts per segment
    // if the cone is closed
    const unsigned int mem = tess * 6 + (!bOpen ? tess * 3 * (radius1 ? 2 : 1) : 0);
    positions.reserve(positions.size() + mem);

    // Now construct all segments
    const ai_real angle_delta = (ai_real)AI_MATH_TWO_PI / tess;
    const ai_real angle_max = (ai_real)AI_MATH_TWO_PI;

    ai_real s = 1.0; // std::cos(angle == 0);
    ai_real t = 0.0; // std::sin(angle == 0);

    for (ai_real angle = 0.0; angle < angle_max;) {
        const aiVector3D v1 = aiVector3D(s * radius1, -halfHeight, t * radius1);
        const aiVector3D v2 = aiVector3D(s * radius2, halfHeight, t * radius2);

        const ai_real next = angle + angle_delta;
        ai_real s2 = std::cos(next);
        ai_real t2 = std::sin(next);

        const aiVector3D v3 = aiVector3D(s2 * radius2, halfHeight, t2 * radius2);
        const aiVector3D v4 = aiVector3D(s2 * radius1, -halfHeight, t2 * radius1);

        positions.push_back(v1);
        positions.push_back(v2);
        positions.push_back(v3);
        positions.push_back(v4);
        positions.push_back(v1);
        positions.push_back(v3);

        if (!bOpen) {
            // generate the end 'cap'
            positions.push_back(aiVector3D(s * radius2, halfHeight, t * radius2));
            positions.push_back(aiVector3D(s2 * radius2, halfHeight, t2 * radius2));
            positions.push_back(aiVector3D(0.0, halfHeight, 0.0));

            if (radius1) {
                // generate the other end 'cap'
                positions.push_back(aiVector3D(s * radius1, -halfHeight, t * radius1));
                positions.push_back(aiVector3D(s2 * radius1, -halfHeight, t2 * radius1));
                positions.push_back(aiVector3D(0.0, -halfHeight, 0.0));
            }
        }
        s = s2;
        t = t2;
        angle = next;
    }

    // Need to flip face order?
    if (SIZE_MAX != old) {
        for (size_t p = old; p < positions.size(); p += 3) {
            std::swap(positions[p], positions[p + 1]);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Build a circle
void StandardShapes::MakeCircle(ai_real radius, unsigned int tess,
        std::vector<aiVector3D> &positions) {
    // Sorry, a circle with less than 3 segments makes ABSOLUTELY NO SENSE
    if (tess < 3 || !radius)
        return;

    radius = std::fabs(radius);

    // We will need 3 vertices per segment
    positions.reserve(positions.size() + tess * 3);

    const ai_real angle_delta = (ai_real)AI_MATH_TWO_PI / tess;
    const ai_real angle_max = (ai_real)AI_MATH_TWO_PI;

    ai_real s = 1.0; // std::cos(angle == 0);
    ai_real t = 0.0; // std::sin(angle == 0);

    for (ai_real angle = 0.0; angle < angle_max;) {
        positions.push_back(aiVector3D(s * radius, 0.0, t * radius));
        angle += angle_delta;
        s = std::cos(angle);
        t = std::sin(angle);
        positions.push_back(aiVector3D(s * radius, 0.0, t * radius));

        positions.push_back(aiVector3D(0.0, 0.0, 0.0));
    }
}

} // namespace Assimp