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/** @file GenUVCoords step */

#include "ComputeUVMappingProcess.h"

#include "Geometry/GeometryUtils.h"

#include "ProcessHelper.h"

#include <assimp/Exceptional.h>

using namespace Assimp;

namespace {

const static aiVector3D base_axis_y(0.0, 1.0, 0.0);

const static aiVector3D base_axis_x(1.0, 0.0, 0.0);

const static aiVector3D base_axis_z(0.0, 0.0, 1.0);

const static ai_real angle_epsilon = ai_real(0.95);

} // namespace

// ------------------------------------------------------------------------------------------------

// Returns whether the processing step is present in the given flag field.

bool ComputeUVMappingProcess::IsActive(unsigned int pFlags) const {

    return (pFlags & aiProcess_GenUVCoords) != 0;

}

// ------------------------------------------------------------------------------------------------

// Find the first empty UV channel in a mesh

inline unsigned int FindEmptyUVChannel(aiMesh *mesh) {

    for (unsigned int m = 0; m < AI_MAX_NUMBER_OF_TEXTURECOORDS; ++m)

        if (!mesh->mTextureCoords[m]) {

            return m;

        }

    ASSIMP_LOG_ERROR("Unable to compute UV coordinates, no free UV slot found");

    return UINT_MAX;

}

// ------------------------------------------------------------------------------------------------

// Try to remove UV seams

void RemoveUVSeams(aiMesh *mesh, aiVector3D *out) {

    // TODO: just a very rough algorithm. I think it could be done

    // much easier, but I don't know how and am currently too tired to

    // to think about a better solution.

    const static ai_real LOWER_LIMIT = ai_real(0.1);

    const static ai_real UPPER_LIMIT = ai_real(0.9);

    const static ai_real LOWER_EPSILON = ai_real(10e-3);

    const static ai_real UPPER_EPSILON = ai_real(1.0 - 10e-3);

    for (unsigned int fidx = 0; fidx < mesh->mNumFaces; ++fidx) {

        const aiFace &face = mesh->mFaces[fidx];

        if (face.mNumIndices < 3) {

            continue; // triangles and polygons only, please

        }

        unsigned int smallV = face.mNumIndices, large = smallV;

        bool zero = false, one = false, round_to_zero = false;

        // Check whether this face lies on a UV seam. We can just guess,

        // but the assumption that a face with at least one very small

        // on the one side and one very large U coord on the other side

        // lies on a UV seam should work for most cases.

        for (unsigned int n = 0; n < face.mNumIndices; ++n) {

            if (out[face.mIndices[n]].x < LOWER_LIMIT) {

                smallV = n;

                // If we have a U value very close to 0 we can't

                // round the others to 0, too.

                if (out[face.mIndices[n]].x <= LOWER_EPSILON)

                    zero = true;

                else

                    round_to_zero = true;

            }

            if (out[face.mIndices[n]].x > UPPER_LIMIT) {

                large = n;

                // If we have a U value very close to 1 we can't

                // round the others to 1, too.

                if (out[face.mIndices[n]].x >= UPPER_EPSILON)

                    one = true;

            }

        }

        if (smallV != face.mNumIndices && large != face.mNumIndices) {

            for (unsigned int n = 0; n < face.mNumIndices; ++n) {

                // If the u value is over the upper limit and no other u

                // value of that face is 0, round it to 0

                if (out[face.mIndices[n]].x > UPPER_LIMIT && !zero)

                    out[face.mIndices[n]].x = 0.0;

                // If the u value is below the lower limit and no other u

                // value of that face is 1, round it to 1

                else if (out[face.mIndices[n]].x < LOWER_LIMIT && !one)

                    out[face.mIndices[n]].x = 1.0;

                // The face contains both 0 and 1 as UV coords. This can occur

                // for faces which have an edge that lies directly on the seam.

                // Due to numerical inaccuracies one U coord becomes 0, the

                // other 1. But we do still have a third UV coord to determine

                // to which side we must round to.

                else if (one && zero) {

                    if (round_to_zero && out[face.mIndices[n]].x >= UPPER_EPSILON)

                        out[face.mIndices[n]].x = 0.0;

                    else if (!round_to_zero && out[face.mIndices[n]].x <= LOWER_EPSILON)

                        out[face.mIndices[n]].x = 1.0;

                }

            }

        }

    }

}

// ------------------------------------------------------------------------------------------------

void ComputeUVMappingProcess::ComputeSphereMapping(aiMesh *mesh, const aiVector3D &axis, aiVector3D *out) {

    aiVector3D center, min, max;

    FindMeshCenter(mesh, center, min, max);

    // If the axis is one of x,y,z run a faster code path. It's worth the extra effort ...

    // currently the mapping axis will always be one of x,y,z, except if the

    // PretransformVertices step is used (it transforms the meshes into worldspace,

    // thus changing the mapping axis)

    if (axis * base_axis_x >= angle_epsilon) {

        // For each point get a normalized projection vector in the sphere,

        // get its longitude and latitude and map them to their respective

        // UV axes. Problems occur around the poles ... unsolvable.

        //

        // The spherical coordinate system looks like this:

        // x = cos(lon)*cos(lat)

        // y = sin(lon)*cos(lat)

        // z = sin(lat)

        //

        // Thus we can derive:

        // lat  = arcsin (z)

        // lon  = arctan (y/x)

        for (unsigned int pnt = 0; pnt < mesh->mNumVertices; ++pnt) {

            const aiVector3D diff = (mesh->mVertices[pnt] - center).Normalize();

            out[pnt] = aiVector3D((std::atan2(diff.z, diff.y) + AI_MATH_PI_F) / AI_MATH_TWO_PI_F,

                    (std::asin(diff.x) + AI_MATH_HALF_PI_F) / AI_MATH_PI_F, 0.0);

        }

    } else if (axis * base_axis_y >= angle_epsilon) {

        // ... just the same again

        for (unsigned int pnt = 0; pnt < mesh->mNumVertices; ++pnt) {

            const aiVector3D diff = (mesh->mVertices[pnt] - center).Normalize();

            out[pnt] = aiVector3D((std::atan2(diff.x, diff.z) + AI_MATH_PI_F) / AI_MATH_TWO_PI_F,

                    (std::asin(diff.y) + AI_MATH_HALF_PI_F) / AI_MATH_PI_F, 0.0);

        }

    } else if (axis * base_axis_z >= angle_epsilon) {

        // ... just the same again

        for (unsigned int pnt = 0; pnt < mesh->mNumVertices; ++pnt) {

            const aiVector3D diff = (mesh->mVertices[pnt] - center).Normalize();

            out[pnt] = aiVector3D((std::atan2(diff.y, diff.x) + AI_MATH_PI_F) / AI_MATH_TWO_PI_F,

                    (std::asin(diff.z) + AI_MATH_HALF_PI_F) / AI_MATH_PI_F, 0.0);

        }

    }

    // slower code path in case the mapping axis is not one of the coordinate system axes

    else {

        aiMatrix4x4 mTrafo;

        aiMatrix4x4::FromToMatrix(axis, base_axis_y, mTrafo);

        // again the same, except we're applying a transformation now

        for (unsigned int pnt = 0; pnt < mesh->mNumVertices; ++pnt) {

            const aiVector3D diff = ((mTrafo * mesh->mVertices[pnt]) - center).Normalize();

            out[pnt] = aiVector3D((std::atan2(diff.y, diff.x) + AI_MATH_PI_F) / AI_MATH_TWO_PI_F,

                    (std::asin(diff.z) + AI_MATH_HALF_PI_F) / AI_MATH_PI_F, 0.0);

        }

    }

    // Now find and remove UV seams. A seam occurs if a face has a tcoord

    // close to zero on the one side, and a tcoord close to one on the

    // other side.

    RemoveUVSeams(mesh, out);

}

// ------------------------------------------------------------------------------------------------

void ComputeUVMappingProcess::ComputeCylinderMapping(aiMesh *mesh, const aiVector3D &axis, aiVector3D *out) {

    aiVector3D center, min, max;

    // If the axis is one of x,y,z run a faster code path. It's worth the extra effort ...

    // currently the mapping axis will always be one of x,y,z, except if the

    // PretransformVertices step is used (it transforms the meshes into worldspace,

    // thus changing the mapping axis)

    if (axis * base_axis_x >= angle_epsilon) {

        FindMeshCenter(mesh, center, min, max);

        const ai_real diff = max.x - min.x;

        // If the main axis is 'z', the z coordinate of a point 'p' is mapped

        // directly to the texture V axis. The other axis is derived from

        // the angle between ( p.x - c.x, p.y - c.y ) and (1,0), where

        // 'c' is the center point of the mesh.

        for (unsigned int pnt = 0; pnt < mesh->mNumVertices; ++pnt) {

            const aiVector3D &pos = mesh->mVertices[pnt];

            aiVector3D &uv = out[pnt];

            uv.y = (pos.x - min.x) / diff;

            uv.x = (std::atan2(pos.z - center.z, pos.y - center.y) + (ai_real)AI_MATH_PI) / (ai_real)AI_MATH_TWO_PI;

        }

    } else if (axis * base_axis_y >= angle_epsilon) {

        FindMeshCenter(mesh, center, min, max);

        const ai_real diff = max.y - min.y;

        // just the same ...

        for (unsigned int pnt = 0; pnt < mesh->mNumVertices; ++pnt) {

            const aiVector3D &pos = mesh->mVertices[pnt];

            aiVector3D &uv = out[pnt];

            uv.y = (pos.y - min.y) / diff;

            uv.x = (std::atan2(pos.x - center.x, pos.z - center.z) + (ai_real)AI_MATH_PI) / (ai_real)AI_MATH_TWO_PI;

        }

    } else if (axis * base_axis_z >= angle_epsilon) {

        FindMeshCenter(mesh, center, min, max);

        const ai_real diff = max.z - min.z;

        // just the same ...

        for (unsigned int pnt = 0; pnt < mesh->mNumVertices; ++pnt) {

            const aiVector3D &pos = mesh->mVertices[pnt];

            aiVector3D &uv = out[pnt];

            uv.y = (pos.z - min.z) / diff;

            uv.x = (std::atan2(pos.y - center.y, pos.x - center.x) + (ai_real)AI_MATH_PI) / (ai_real)AI_MATH_TWO_PI;

        }

    }

    // slower code path in case the mapping axis is not one of the coordinate system axes

    else {

        aiMatrix4x4 mTrafo;

        aiMatrix4x4::FromToMatrix(axis, base_axis_y, mTrafo);

        FindMeshCenterTransformed(mesh, center, min, max, mTrafo);

        const ai_real diff = max.y - min.y;

        // again the same, except we're applying a transformation now

        for (unsigned int pnt = 0; pnt < mesh->mNumVertices; ++pnt) {

            const aiVector3D pos = mTrafo * mesh->mVertices[pnt];

            aiVector3D &uv = out[pnt];

            uv.y = (pos.y - min.y) / diff;

            uv.x = (std::atan2(pos.x - center.x, pos.z - center.z) + (ai_real)AI_MATH_PI) / (ai_real)AI_MATH_TWO_PI;

        }

    }

    // Now find and remove UV seams. A seam occurs if a face has a tcoord

    // close to zero on the one side, and a tcoord close to one on the

    // other side.

    RemoveUVSeams(mesh, out);

}

// ------------------------------------------------------------------------------------------------

void ComputeUVMappingProcess::ComputePlaneMapping(aiMesh *mesh, const aiVector3D &axis, aiVector3D *out) {

    ai_real diffu, diffv;

    aiVector3D center, min, max;

    // If the axis is one of x,y,z run a faster code path. It's worth the extra effort ...

    // currently the mapping axis will always be one of x,y,z, except if the

    // PretransformVertices step is used (it transforms the meshes into worldspace,

    // thus changing the mapping axis)

    if (axis * base_axis_x >= angle_epsilon) {

        FindMeshCenter(mesh, center, min, max);

        diffu = max.z - min.z;

        diffv = max.y - min.y;

        for (unsigned int pnt = 0; pnt < mesh->mNumVertices; ++pnt) {

            const aiVector3D &pos = mesh->mVertices[pnt];

            out[pnt].Set((pos.z - min.z) / diffu, (pos.y - min.y) / diffv, 0.0);

        }

    } else if (axis * base_axis_y >= angle_epsilon) {

        FindMeshCenter(mesh, center, min, max);

        diffu = max.x - min.x;

        diffv = max.z - min.z;

        for (unsigned int pnt = 0; pnt < mesh->mNumVertices; ++pnt) {

            const aiVector3D &pos = mesh->mVertices[pnt];

            out[pnt].Set((pos.x - min.x) / diffu, (pos.z - min.z) / diffv, 0.0);

        }

    } else if (axis * base_axis_z >= angle_epsilon) {

        FindMeshCenter(mesh, center, min, max);

        diffu = max.x - min.x;

        diffv = max.y - min.y;

        for (unsigned int pnt = 0; pnt < mesh->mNumVertices; ++pnt) {

            const aiVector3D &pos = mesh->mVertices[pnt];

            out[pnt].Set((pos.x - min.x) / diffu, (pos.y - min.y) / diffv, 0.0);

        }

    }

    // slower code path in case the mapping axis is not one of the coordinate system axes

    else {

        aiMatrix4x4 mTrafo;

        aiMatrix4x4::FromToMatrix(axis, base_axis_y, mTrafo);

        FindMeshCenterTransformed(mesh, center, min, max, mTrafo);

        diffu = max.x - min.x;

        diffv = max.z - min.z;

        // again the same, except we're applying a transformation now

        for (unsigned int pnt = 0; pnt < mesh->mNumVertices; ++pnt) {

            const aiVector3D pos = mTrafo * mesh->mVertices[pnt];

            out[pnt].Set((pos.x - min.x) / diffu, (pos.z - min.z) / diffv, 0.0);

        }

    }

    // shouldn't be necessary to remove UV seams ...

}

// ------------------------------------------------------------------------------------------------

void ComputeUVMappingProcess::ComputeBoxMapping(aiMesh *, aiVector3D *) {

    ASSIMP_LOG_ERROR("Mapping type currently not implemented");

}

// ------------------------------------------------------------------------------------------------

void ComputeUVMappingProcess::Execute(aiScene *pScene) {

    ASSIMP_LOG_DEBUG("GenUVCoordsProcess begin");

    char buffer[1024];

    if (pScene->mFlags & AI_SCENE_FLAGS_NON_VERBOSE_FORMAT) {

        throw DeadlyImportError("Post-processing order mismatch: expecting pseudo-indexed (\"verbose\") vertices here");

    }

    std::list<MappingInfo> mappingStack;

    // Iterate through all materials and search for non-UV mapped textures

    for (unsigned int i = 0; i < pScene->mNumMaterials; ++i) {

        mappingStack.clear();

        aiMaterial *mat = pScene->mMaterials[i];

        if (mat == nullptr) {

            ASSIMP_LOG_INFO("Material pointer in nullptr, skipping.");

            continue;

        }

        for (unsigned int a = 0; a < mat->mNumProperties; ++a) {

            aiMaterialProperty *prop = mat->mProperties[a];

            if (!::strcmp(prop->mKey.data, "$tex.mapping")) {

                aiTextureMapping &mapping = *((aiTextureMapping *)prop->mData);

                if (aiTextureMapping_UV != mapping) {

                    if (!DefaultLogger::isNullLogger()) {

                        ai_snprintf(buffer, 1024, "Found non-UV mapped texture (%s,%u). Mapping type: %s",

                                aiTextureTypeToString((aiTextureType)prop->mSemantic), prop->mIndex,

                                MappingTypeToString(mapping));

                        ASSIMP_LOG_INFO(buffer);

                    }

                    if (aiTextureMapping_OTHER == mapping)

                        continue;

                    MappingInfo info(mapping);

                    // Get further properties - currently only the major axis

                    for (unsigned int a2 = 0; a2 < mat->mNumProperties; ++a2) {

                        aiMaterialProperty *prop2 = mat->mProperties[a2];

                        if (prop2->mSemantic != prop->mSemantic || prop2->mIndex != prop->mIndex)

                            continue;

                        if (!::strcmp(prop2->mKey.data, "$tex.mapaxis")) {

                            info.axis = *((aiVector3D *)prop2->mData);

                            break;

                        }

                    }

                    unsigned int idx(99999999);

                    // Check whether we have this mapping mode already

                    std::list<MappingInfo>::iterator it = std::find(mappingStack.begin(), mappingStack.end(), info);

                    if (mappingStack.end() != it) {

                        idx = (*it).uv;

                    } else {

                        /*  We have found a non-UV mapped texture. Now

                         *   we need to find all meshes using this material

                         *   that we can compute UV channels for them.

                         */

                        for (unsigned int m = 0; m < pScene->mNumMeshes; ++m) {

                            aiMesh *mesh = pScene->mMeshes[m];

                            unsigned int outIdx = 0;

                            if (mesh->mMaterialIndex != i || (outIdx = FindEmptyUVChannel(mesh)) == UINT_MAX ||

                                    !mesh->mNumVertices) {

                                continue;

                            }

                            // Allocate output storage

                            aiVector3D *p = mesh->mTextureCoords[outIdx] = new aiVector3D[mesh->mNumVertices];

                            switch (mapping) {

                            case aiTextureMapping_SPHERE:

                                ComputeSphereMapping(mesh, info.axis, p);

                                break;

                            case aiTextureMapping_CYLINDER:

                                ComputeCylinderMapping(mesh, info.axis, p);

                                break;

                            case aiTextureMapping_PLANE:

                                ComputePlaneMapping(mesh, info.axis, p);

                                break;

                            case aiTextureMapping_BOX:

                                ComputeBoxMapping(mesh, p);

                                break;

                            default:

                                ai_assert(false);

                            }

                            if (m && idx != outIdx) {

                                ASSIMP_LOG_WARN("UV index mismatch. Not all meshes assigned to "

                                                "this material have equal numbers of UV channels. The UV index stored in  "

                                                "the material structure does therefore not apply for all meshes. ");

                            }

                            idx = outIdx;

                        }

                        info.uv = idx;

                        mappingStack.push_back(info);

                    }

                    // Update the material property list

                    mapping = aiTextureMapping_UV;

                    ((aiMaterial *)mat)->AddProperty(&idx, 1, AI_MATKEY_UVWSRC(prop->mSemantic, prop->mIndex));

                }

            }

        }

    }

    ASSIMP_LOG_DEBUG("GenUVCoordsProcess finished");

}