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// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
#ifndef QSSGLIGHTMAPUVGENERATOR_P_H
#define QSSGLIGHTMAPUVGENERATOR_P_H
//
// W A R N I N G
// -------------
//
// This file is not part of the Qt API. It exists purely as an
// implementation detail. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
#include <QtQuick3DUtils/private/qssgmesh_p.h>
QT_BEGIN_NAMESPACE
struct QSSGLightmapUVGeneratorResult
{
QByteArray lightmapUVChannel;
QVector<quint32> vertexMap;
QByteArray indexData;
quint32 lightmapWidth = 0;
quint32 lightmapHeight = 0;
bool isValid() const {
return !lightmapUVChannel.isEmpty() && !vertexMap.isEmpty();
}
};
class Q_QUICK3DUTILS_EXPORT QSSGLightmapUVGenerator
{
public:
// Takes in position, normals, UV0, indices and returns a new lightmap UV
// channel, new index data, and a mapping to original vertices.
//
// The topology must be triangles. The position data is expected to contain
// 3 component float positions. normals is expected to contain 3 component
// float normal vectors. uv0 is expected to contain 2 component float UV
// coordinates. When not available, normals and uv0 can be left empty.
//
// The resulting index data has always the same number of indices as the
// original, but regardless of the original component type, the new data
// always has a component type of uint32.
//
// The resulting lightmapUVChannel contains 2 component floats. There can
// be more lightmap UVs than input positions, because the unwrapping
// process may add extra vertices to avoid seams. The new vertices always
// correspond to an original vertex. That is why the result also has a list
// that has one element for each UV in the lightmap UV data, the value
// being an index of a vertex in the original position channel. This
// mapping must be used by the caller to grow and rewrite all vertex input
// data (position, normals, UVs, etc.) so that the count of their elements
// matches the lightmap UV channel.
//
// texelsPerUnit
// Unit to texel scale. e.g. a 1x1 quad with texelsPerUnit of 32 will take
// up approximately 32x32 texels in the atlas.
//
QSSGLightmapUVGeneratorResult run(const QByteArray &positions,
const QByteArray &normals,
const QByteArray &uv0,
const QByteArray &index,
QSSGMesh::Mesh::ComponentType indexComponentType,
float texelsPerUnit);
// source is of N elements of componentCount * sizeof(T) bytes each. The
// returned data is M elements of componentCount * sizeof(T) bytes each, where
// M >= N. vertexMap is the mapping table with M elements where each element
// is an index in range [0, N-1].
template<typename T>
static QByteArray remap(const QByteArray &source, const QVector<quint32> &vertexMap, int componentCount)
{
if (source.isEmpty())
return QByteArray();
const T *src = reinterpret_cast<const T *>(source.constData());
const int byteStride = sizeof(T) * componentCount;
QByteArray result(vertexMap.size() * byteStride, Qt::Uninitialized);
T *dst = reinterpret_cast<T *>(result.data());
for (int i = 0, count = vertexMap.size(); i != count; ++i) {
const quint32 originalVertexIndex = vertexMap[i];
for (int j = 0; j < componentCount; ++j)
*dst++ = src[originalVertexIndex * componentCount + j];
}
return result;
}
};
QT_END_NAMESPACE
#endif // QSSGLIGHTMAPUVGENERATOR_P_H
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