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Allow transformations for HexGridVisual (instead of just 'zoom') #180

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Merged
sebsjames merged 3 commits into from
Oct 14, 2026
Merged

Allow transformations for HexGridVisual (instead of just 'zoom') #180

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454a7c8
Adds code comment showing how to scale/reflect the HexGridVisual
sebsjames Oct 14, 2026
8e6bba6
Replace scalar zoom with a transform matrix for more flexibility
sebsjames Oct 14, 2026
ac8a74d
Adds a left-right reflection convenience function
sebsjames Oct 14, 2026
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3 changes: 3 additions & 0 deletions examples/hexgrid.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -77,6 +77,9 @@ int main()
hgv2->setScalarData (&data2);
hgv2->hexVisMode = visMode;
hgv2->zScale.null_scaling();
// You can transform the view of the hexgrid in HexGridVisual (transforms may also be applied to the underlying hexgrid)
// This applies a scaling first, and then a reflection.
//hgv2->tfm = sm::mat<float, 3>::reflection (sm::vec<float>::ux()) * sm::mat<float, 3>::identity() * 0.5f;
hgv2->addLabel ("hexalign::flat_up", sm::vec<>{ -hg1.width()/2.6f, -hg1.width()/1.6f }, mplot::TextFeatures(0.02f));
hgv2->finalize();

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2 changes: 1 addition & 1 deletion examples/hexgrid_fft.cpp
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Expand Up @@ -173,7 +173,7 @@ int main()
// Real part of hexgrid FFT
auto fhgv = std::make_unique<mplot::HexGridVisual<float, sm::hexalign::flat_up>>(hfft.hgf.get(), sm::vec<float>{3.0f, 0.0f});
fhgv->set_parent (v.get_id());
fhgv->zoom = (hfft.Uscale);
fhgv->set_zoom (hfft.Uscale);
fhgv->zScale.null_scaling();
fhgv->setScalarData (&fft_r);
fhgv->cm.setType (mplot::ColourMapType::GreyscaleInv);
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12 changes: 6 additions & 6 deletions examples/hexgrid_image_fft.cpp
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Expand Up @@ -104,7 +104,7 @@ int main (int argc, char** argv)
// Show the real part of FFT on a hexgrid
auto fhgv = std::make_unique<mplot::HexGridVisual<float, sm::hexalign::flat_up>>(hfft.hgf.get(), o + sm::vec<float>{ hgw, fhgw * 0.6f });
fhgv->set_parent (v.get_id());
fhgv->zoom = myUscale;
fhgv->set_zoom (myUscale);
fhgv->setScalarData (&fft_r);
fhgv->colourScale.compute_scaling (-1200, 1200);
fhgv->cm.setType (mplot::ColourMapType::CET_D13);
Expand All @@ -116,7 +116,7 @@ int main (int argc, char** argv)
// Show the imaginary part of FFT on a hexgrid
fhgv = std::make_unique<mplot::HexGridVisual<float, sm::hexalign::flat_up>>(hfft.hgf.get(), o + sm::vec<float>{ hgw, -fhgw * 0.6f });
fhgv->set_parent (v.get_id());
fhgv->zoom = myUscale;
fhgv->set_zoom (myUscale);
fhgv->setScalarData (&fft_i);
fhgv->colourScale.compute_scaling (-1200, 1200);
fhgv->cm.setType (mplot::ColourMapType::CET_D13);
Expand Down Expand Up @@ -173,7 +173,7 @@ int main (int argc, char** argv)
// real
fhgv = std::make_unique<mplot::HexGridVisual<float, sm::hexalign::flat_up>>(hfft.hgf.get(), o + sm::vec<float>{ hgw, -hgw * 1.5f + fhgw * 0.6f });
fhgv->set_parent (v.get_id());
fhgv->zoom = myUscale;
fhgv->set_zoom (myUscale);
fhgv->setScalarData (&fft_r);
fhgv->colourScale.compute_scaling (-1200, 1200);
fhgv->cm.setType (mplot::ColourMapType::CET_D13);
Expand All @@ -184,7 +184,7 @@ int main (int argc, char** argv)
// imag
fhgv = std::make_unique<mplot::HexGridVisual<float, sm::hexalign::flat_up>>(hfft.hgf.get(), o + sm::vec<float>{ hgw, -hgw * 1.5f - fhgw * 0.6f });
fhgv->set_parent (v.get_id());
fhgv->zoom = myUscale;
fhgv->set_zoom (myUscale);
fhgv->setScalarData (&fft_i);
fhgv->colourScale.compute_scaling (-1200, 1200);
fhgv->cm.setType (mplot::ColourMapType::CET_D13);
Expand All @@ -206,7 +206,7 @@ int main (int argc, char** argv)
// real
fhgv = std::make_unique<mplot::HexGridVisual<float, sm::hexalign::flat_up>>(hfft.hgf.get(), o + sm::vec<float>{ hgw, -hgw * 3.0f + fhgw * 0.6f });
fhgv->set_parent (v.get_id());
fhgv->zoom = myUscale;
fhgv->set_zoom (myUscale);
fhgv->setScalarData (&fft_r);
fhgv->colourScale.compute_scaling (-1200, 1200);
fhgv->cm.setType (mplot::ColourMapType::CET_D13);
Expand All @@ -217,7 +217,7 @@ int main (int argc, char** argv)
// image
fhgv = std::make_unique<mplot::HexGridVisual<float, sm::hexalign::flat_up>>(hfft.hgf.get(), o + sm::vec<float>{ hgw, -hgw * 3.0f - fhgw * 0.6f });
fhgv->set_parent (v.get_id());
fhgv->zoom = myUscale;
fhgv->set_zoom (myUscale);
fhgv->setScalarData (&fft_i);
fhgv->colourScale.compute_scaling (-1200, 1200);
fhgv->cm.setType (mplot::ColourMapType::CET_D13);
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49 changes: 31 additions & 18 deletions mplot/HexGridVisual.cppm
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Original file line number Diff line number Diff line change
Expand Up @@ -52,8 +52,18 @@ export namespace mplot
//! something, so that it is visible.
void markHex (std::uint32_t hi) { this->markedHexes.insert(hi); }

//! Zoom factor
float zoom = 1.0f;
void set_zoom (const float factor)
{
this->tfm = (sm::mat<float, 3>::identity() * factor) * this->tfm;
}

void reflect_lr()
{
this->tfm = sm::mat<float, 3>::reflection(sm::vec<float>::ux()) * this->tfm;
}

//! scalar 'zoom' has been replaced with a transform matrix to allow zoom, but also flip or rotate
sm::mat<float, 3> tfm;

//! Show a set of hexes at the zero?
bool zerogrid = false;
Expand Down Expand Up @@ -246,18 +256,21 @@ export namespace mplot
// If dataCoords has been populated, use these for hex positions, allowing for
// mapping of the 2D hexgrid onto a 3D manifold.
if (this->dataCoords == nullptr) {
sm::vec<T, 3> crd = { this->hg->d_x[hi], this->hg->d_y[hi], this->dcopy[hi] };
sm::vec<float, 3> p = this->tfm * crd.template as<float>();
if (update == false) {
this->vertexPositions[hi * 3] = this->zoom * this->hg->d_x[hi];
this->vertexPositions[hi * 3 + 1] = this->zoom * this->hg->d_y[hi];
this->vertexPositions[hi * 3] = p[0];
this->vertexPositions[hi * 3 + 1] = p[1];
}
this->vertexPositions[hi * 3 + 2] = this->zoom * this->dcopy[hi];
this->vertexPositions[hi * 3 + 2] = p[2];

} else { // Otherwise use the positions directly in the hexgrid:
sm::vec<float, 3> p = this->tfm * (*this->dataCoords)[hi]; // sm::vec<float, 3>{ (*this->dataCoords)[hi][0], (*this->dataCoords)[hi][1], (*this->dataCoords)[hi][2] };
if (update == false) {
this->vertexPositions[hi * 3] = (*this->dataCoords)[hi][0];
this->vertexPositions[hi * 3 + 1] = (*this->dataCoords)[hi][1];
this->vertexPositions[hi * 3] = p[0];
this->vertexPositions[hi * 3 + 1] = p[1];
}
this->vertexPositions[hi * 3 + 2] = (*this->dataCoords)[hi][2];
this->vertexPositions[hi * 3 + 2] = p[2];
}
if (this->markedHexes.count(hi)) {
this->vertexColors[hi * 3] = blkclr[0];
Expand Down Expand Up @@ -353,6 +366,9 @@ export namespace mplot
sm::vec<float> coordN4 = {};
sm::vec<float> coordN5 = {};

// The rotation from the transformation in the hexgrid (if any)
sm::mat<float, 3> lt (this->hg->tfm.template as<float>());

for (std::uint32_t hi = 0; hi < nhex; ++hi) {

if (this->dataCoords == nullptr) {
Expand Down Expand Up @@ -403,10 +419,7 @@ export namespace mplot

// Use the centre position as the first location for finding the normal vector
vtx_0 = this->dataCoords == nullptr ? sm::vec<float>{ _x, _y, datumC } : coordC;
this->vertex_push (this->zoom * vtx_0, this->vertexPositions);

// The rotation from the transformation in the hexgrid (if any)
sm::mat<float, 3> lt (this->hg->tfm.template as<float>());
this->vertex_push ((this->tfm * vtx_0), this->vertexPositions);

// A hexagon corner/vertex position
sm::vec<float> crnr = {};
Expand Down Expand Up @@ -447,7 +460,7 @@ export namespace mplot
vtx_1 = coordC;
}
}
this->vertex_push (this->zoom * vtx_1, this->vertexPositions);
this->vertex_push (this->tfm * vtx_1, this->vertexPositions);


// SE vertex
Expand Down Expand Up @@ -482,7 +495,7 @@ export namespace mplot
vtx_2 = coordC;
}
}
this->vertex_push (this->zoom * vtx_2, this->vertexPositions);
this->vertex_push (this->tfm * vtx_2, this->vertexPositions);


// S
Expand Down Expand Up @@ -517,7 +530,7 @@ export namespace mplot
vtx_tmp = coordC;
}
}
this->vertex_push (this->zoom * vtx_tmp, this->vertexPositions);
this->vertex_push (this->tfm * vtx_tmp, this->vertexPositions);

// SW
if (this->dataCoords == nullptr) {
Expand Down Expand Up @@ -551,7 +564,7 @@ export namespace mplot
vtx_tmp = coordC;
}
}
this->vertex_push (this->zoom * vtx_tmp, this->vertexPositions);
this->vertex_push (this->tfm * vtx_tmp, this->vertexPositions);

// NW
if (this->dataCoords == nullptr) {
Expand Down Expand Up @@ -585,7 +598,7 @@ export namespace mplot
vtx_tmp = coordC;
}
}
this->vertex_push (this->zoom * vtx_tmp, this->vertexPositions);
this->vertex_push (this->tfm * vtx_tmp, this->vertexPositions);

// N
if (this->dataCoords == nullptr) {
Expand Down Expand Up @@ -619,7 +632,7 @@ export namespace mplot
vtx_tmp = coordC;
}
}
this->vertex_push (this->zoom * vtx_tmp, this->vertexPositions);
this->vertex_push (this->tfm * vtx_tmp, this->vertexPositions);

// From vtx_0,1,2 compute normal. This sets the correct normal, but note
// that there is only one 'layer' of vertices; the back of the
Expand Down
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