Method GenerateTangents

Source/Engine/Graphics/Models/ModelData.Tool.cpp:559–746

#endif

bool MeshData::GenerateTangents(float smoothingAngle)
{
    if (Positions.IsEmpty() || Indices.IsEmpty())
    {
        LOG(Warning, "Missing vertex or index data to generate tangents.");
        return true;
    }
    if (Normals.IsEmpty() || UVs.IsEmpty())
    {
        LOG(Warning, "Missing normals or texcoords data to generate tangents.");
        return true;
    }
    PROFILE_CPU();

    const auto startTime = Platform::GetTimeSeconds();
    const int32 vertexCount = Positions.Count();
    const int32 indexCount = Indices.Count();
    Tangents.Resize(vertexCount, false);
    smoothingAngle = Math::Clamp(smoothingAngle, 0.0f, 45.0f);

#if USE_MIKKTSPACE
    SMikkTSpaceInterface callbacks = {
        GetNumFaces,
        GetNumVerticesOfFace,
        GetPosition,
        GetNormal,
        GetTexCoord,
        SetTSpaceBasic,
        nullptr
    };
    const SMikkTSpaceContext context = { &callbacks, this };
    BitangentSigns.Resize(vertexCount, false);
    genTangSpace(&context, 180.0f - smoothingAngle);
#else
    const float angleEpsilon = 0.9999f;
    BitArray<> vertexDone;
    vertexDone.Resize(vertexCount);
    vertexDone.SetAll(false);

    const Float3* meshNorm = Normals.Get();
    const Float2* meshTex = UVs[0].Get();
    Float3* meshTang = Tangents.Get();

    // Calculate the tangent per-triangle
    Float3 min, max;
    min = max = Positions[Indices[0]];
    for (int32 i = 0; i < indexCount; i += 3)
    {
        const int32 p0 = Indices[i + 0], p1 = Indices[i + 1], p2 = Indices[i + 2];

        const Float3 v0 = Positions[p0];
        const Float3 v1 = Positions[p1];
        const Float3 v2 = Positions[p2];

        Float3::Min(min, v0, min);
        Float3::Min(min, v1, min);
        Float3::Min(min, v2, min);