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A multi-coloured rhombohedron showing triangles. Useful for debug/test #77

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Merged
sebsjames merged 2 commits into from
Sep 25, 2025
Merged

A multi-coloured rhombohedron showing triangles. Useful for debug/test #77

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5f53099
WIP
sebsjames Sep 25, 2025
2afc510
Completes the multi-coloured cube example
sebsjames Sep 25, 2025
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7 changes: 4 additions & 3 deletions examples/cube.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -14,15 +14,16 @@ int main()
// Parameters of the model
sm::vec<float, 3> offset = { 1, -0.5, -0.5 }; // a within-scene offset

sm::vec<float, 3> e1 = { 1, 0, 0 };
sm::vec<float, 3> e2 = { 0, 1, 0 };
sm::vec<float, 3> e3 = { 0, 0, 1 };
sm::vec<float, 3> e1 = { 1, 0, 0 };
sm::vec<float, 3> e2 = { 0, 1, 0 };
sm::vec<float, 3> e3 = { 0, 0, 1 };

sm::vec<float, 3> colour1 = { 0.35, 0.76, 0.98 }; // RGB colour triplet

auto rv = std::make_unique<mplot::RhomboVisual<>> (offset, e1, e2, e3, colour1);
v.bindmodel (rv);
rv->name = "Cube.002";
rv->facecm = mplot::ColourMapType::Rainbow; // Try Rainbow, Batlow, Tofino
rv->finalize();
v.addVisualModel (rv);

Expand Down
87 changes: 87 additions & 0 deletions mplot/RhomboVisual.h
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#include <array>
#include <sm/vec>
#include <mplot/VisualModel.h>
#include <mplot/ColourMap.h>

namespace mplot {

Expand All @@ -20,6 +21,15 @@ namespace mplot {

//! Initialize vertex buffer objects and vertex array object.
void initializeVertices() override
{
if (this->facecm == mplot::ColourMapType::Fixed) {
this->vertices_singlecolour();
} else {
this->vertices_multicolour();
}
}

void vertices_singlecolour()
{
// Compute the face normals
sm::vec<float> _n1 = this->edge1.cross (this->edge2);
Expand Down Expand Up @@ -86,11 +96,88 @@ namespace mplot {
}
}

// Allowing a colour for each face. May be useful for debugging
void vertices_multicolour()
{
// Compute the face normals
sm::vec<float> _n1 = this->edge1.cross (this->edge2);
_n1.renormalize();
sm::vec<float> _n2 = this->edge2.cross (this->edge3);
_n2.renormalize();
sm::vec<float> _n3 = this->edge1.cross (this->edge3);
_n3.renormalize();

// First corner of rhombohedron is at model-frame's origin
sm::vec<float> o = {0,0,0};

// Push positions and normals for 24 vertices to make up the rhombohedron; *6* for each face.
// Front face needs 6 vertices
this->vertex_push (o, this->vertexPositions);
this->vertex_push (o + this->edge1, this->vertexPositions);
this->vertex_push (o + this->edge3, this->vertexPositions);
this->vertex_push (o + this->edge3, this->vertexPositions); // extra
this->vertex_push (o + this->edge1, this->vertexPositions); // extra
this->vertex_push (o + this->edge1 + this->edge3, this->vertexPositions);
for (unsigned short i = 0U; i < 6U; ++i) { this->vertex_push (_n3, this->vertexNormals); }
// Top face
this->vertex_push (o + this->edge3, this->vertexPositions);
this->vertex_push (o + this->edge1 + this->edge3, this->vertexPositions);
this->vertex_push (o + this->edge2 + this->edge3, this->vertexPositions);
this->vertex_push (o + this->edge2 + this->edge3, this->vertexPositions); // extra
this->vertex_push (o + this->edge1 + this->edge3, this->vertexPositions); // extra
this->vertex_push (o + this->edge2 + this->edge1 + this->edge3, this->vertexPositions);
for (unsigned short i = 0U; i < 6U; ++i) { this->vertex_push (_n1, this->vertexNormals); }
// Back face
this->vertex_push (o + this->edge2 + this->edge3, this->vertexPositions);
this->vertex_push (o + this->edge2 + this->edge1 + this->edge3, this->vertexPositions);
this->vertex_push (o + this->edge2, this->vertexPositions);
this->vertex_push (o + this->edge2, this->vertexPositions); // extra
this->vertex_push (o + this->edge2 + this->edge1 + this->edge3, this->vertexPositions); // extra
this->vertex_push (o + this->edge2 + this->edge1, this->vertexPositions);
for (unsigned short i = 0U; i < 6U; ++i) { this->vertex_push (-_n3, this->vertexNormals); }
// Bottom face
this->vertex_push (o + this->edge2, this->vertexPositions);
this->vertex_push (o + this->edge2 + this->edge1, this->vertexPositions);
this->vertex_push (o, this->vertexPositions);
this->vertex_push (o, this->vertexPositions); // extra
this->vertex_push (o + this->edge2 + this->edge1, this->vertexPositions); // extra
this->vertex_push (o + this->edge1, this->vertexPositions);
for (unsigned short i = 0U; i < 6U; ++i) { this->vertex_push (-_n1, this->vertexNormals); }
// Left face
this->vertex_push (o + this->edge2, this->vertexPositions);
this->vertex_push (o, this->vertexPositions);
this->vertex_push (o + this->edge2 + this->edge3, this->vertexPositions);
this->vertex_push (o + this->edge2 + this->edge3, this->vertexPositions); // extra
this->vertex_push (o, this->vertexPositions); // extra
this->vertex_push (o + this->edge3, this->vertexPositions);
for (unsigned short i = 0U; i < 6U; ++i) { this->vertex_push (-_n2, this->vertexNormals); }
// Right face
this->vertex_push (o + this->edge1, this->vertexPositions);
this->vertex_push (o + this->edge1 + this->edge2, this->vertexPositions);
this->vertex_push (o + this->edge1 + this->edge3, this->vertexPositions);
this->vertex_push (o + this->edge1 + this->edge3, this->vertexPositions); // extra
this->vertex_push (o + this->edge1 + this->edge2, this->vertexPositions); // extra
this->vertex_push (o + this->edge1 + this->edge2 + this->edge3, this->vertexPositions);
for (unsigned short i = 0U; i < 6U; ++i) { this->vertex_push (_n2, this->vertexNormals); }

// Vertex colours are NOT all the same
mplot::ColourMap<float> cm (this->facecm);
for (unsigned short i = 0U; i < 36U; i += 3) {
this->vertex_push (cm.convert(static_cast<float>(i) / 35.0f), this->vertexColors);
this->vertex_push (cm.convert(static_cast<float>(i) / 35.0f), this->vertexColors);
this->vertex_push (cm.convert(static_cast<float>(i) / 35.0f), this->vertexColors);
}

// Indices for 6 faces.
for (unsigned short i = 0U; i < 36U; ++i) { this->indices.push_back (this->idx++); }
}

//! Three vectors define the Rhombohedron and we use a single colour
sm::vec<float, 3> edge1 = {0.0f, 0.0f, 0.0f};
sm::vec<float, 3> edge2 = {0.0f, 0.0f, 0.0f};
sm::vec<float, 3> edge3 = {0.0f, 0.0f, 0.0f};
std::array<float, 3> col = {0.0f, 0.0f, 1.0f};
mplot::ColourMapType facecm = mplot::ColourMapType::Fixed; // if so, use col
};

} // namespace mplot