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// Copyright (C) 2020 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
#include "custominstancing.h"
#include <math.h>
#include <QMatrix4x4>
struct InstanceTableEntry {
QVector4D row0;
QVector4D row1;
QVector4D row2;
QVector4D color;
QVector4D instanceData;
};
void CustomInstancing::setInstanceCount(int instanceCount)
{
if (m_instanceCount == instanceCount)
return;
m_instanceCount = instanceCount;
emit instanceCountChanged(m_instanceCount);
}
QByteArray CustomInstancing::getInstanceBuffer(int *instanceCount)
{
QByteArray instanceData;
if (instanceCount)
*instanceCount = m_instanceCount;
if (m_instanceCount == 0)
return instanceData;
instanceData.resize(m_instanceCount * 20 * sizeof(float));
auto array = reinterpret_cast<InstanceTableEntry*>(instanceData.data());
const int rows = floor(sqrt(m_instanceCount));
const int columns = m_instanceCount/rows;
for (int i = 0; i < m_instanceCount; ++i) {
QMatrix4x4 xform;
int ix = i % columns;
int iy = i / columns;
float x = 100.0 * (ix - columns/2);
float y = 100.0 * (iy - rows/2);
float z = (x*x + y*y)/1000;
xform(0, 3) += x;
xform(1, 3) += y;
xform(2, 3) += z;
float scale = 0.75;
xform(0, 0) = scale;
xform(1, 1) = scale;
xform(2, 2) = scale;
QVector4D color(float(ix)/columns, float(iy)/columns, 1.0, float(i) / m_instanceCount);
array[i] = {
xform.row(0),
xform.row(1),
xform.row(2),
color,
{}
};
}
return instanceData;
}
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