Line to Spline with CatmullRom interpolation

src/noggit/rendering/Primitives.cpp

@@ -503,15 +503,32 @@ void Square::setup_buffers()
       _buffers_are_setup = true;
   }*/
 
+  void Line::initSpline()
+  {
+      draw(glm::mat4x4{},
+          std::vector<glm::vec3>{ {}, {} },
+          glm::vec4{},
+          false);
+  }
+
   void Line::draw(glm::mat4x4 const& mvp
       , std::vector<glm::vec3> const points
       , glm::vec4 const& color
+      , bool spline
   )
   {
       if (points.size() < 2)
           return;
 
+      if (!spline || points.size() == 2)
+      {
           setup_buffers(points);
+      }
+      else
+      {
+          initSpline();
+          setup_buffers_interpolated(points);
+      }
 
       OpenGL::Scoped::use_program line_shader{ *_program.get() };
 
@@ -536,6 +553,73 @@ void Square::setup_buffers()
           indices.push_back(i);
       }
 
+      setup_shader(vertices, indices);
+  }
+
+  void Line::setup_buffers_interpolated(std::vector<glm::vec3> const points)
+  {
+      const float tension = 0.5f;
+
+      std::vector<glm::vec3> tempPoints;
+      tempPoints.push_back(points[0]);
+
+      for (auto const& p : points)
+          tempPoints.push_back(p);
+
+      tempPoints.push_back(points[points.size() - 1]);
+
+      std::vector<glm::vec3> vertices;
+      std::vector<std::uint16_t> indices;
+
+      for (int i = 1; i < tempPoints.size() - 2; i++)
+      {
+          auto s = tension * 2.f;
+          auto p0 = tempPoints[i - 1];
+          auto p1 = tempPoints[i + 0];
+          auto p2 = tempPoints[i + 1];
+          auto p3 = tempPoints[i + 2];
+
+          glm::vec3 m1(
+              (p2.x - p0.x) / s,
+              (p2.y - p0.y) / s,
+              (p2.z - p0.z) / s
+          );
+
+          glm::vec3 m2(
+              (p3.x - p1.x) / s,
+              (p3.y - p1.y) / s,
+              (p3.z - p1.z) / s
+          );
+
+          vertices.push_back(interpolate(0, p1, p2, m1, m2));
+
+          for (float t = 0.01f; t < 1.f; t += 0.01f)
+              vertices.push_back(interpolate(t, p1, p2, m1, m2));
+
+          vertices.push_back(interpolate(1, p1, p2, m1, m2));
+      }
+
+      for (int i = 0; i < vertices.size(); ++i)
+      {
+          indices.push_back(i);
+      }
+
+      setup_shader(vertices, indices);
+  }
+
+  glm::vec3 Line::interpolate(float t, glm::vec3 p0, glm::vec3 p1, glm::vec3 m0, glm::vec3 m1)
+  {
+      auto c = 2 * t * t * t - 3 * t * t;
+      auto c0 = c + 1;
+      auto c1 = t * t * t - 2 * t * t + t;
+      auto c2 = -c;
+      auto c3 = t * t * t - t * t;
+
+      return (c0 * p0 + c1 * m0 + c2 * p1 + c3 * m1);
+  }
+
+  void Line::setup_shader(std::vector<glm::vec3> vertices, std::vector<std::uint16_t> indices)
+  {
       _indice_count = (int)indices.size();
       _program.reset(new OpenGL::program(
           {
@@ -544,8 +628,8 @@ void Square::setup_buffers()
           }
       ));
 
-      gl.bufferData<GL_ARRAY_BUFFER, glm::vec3> (_vertices_vbo, vertices, GL_STATIC_DRAW);
-      gl.bufferData<GL_ELEMENT_ARRAY_BUFFER, std::uint16_t> (_indices_vbo, indices, GL_STATIC_DRAW);
+      gl.bufferData<GL_ARRAY_BUFFER, glm::vec3>(_vertices_vbo, vertices, GL_STATIC_DRAW);
+      gl.bufferData<GL_ELEMENT_ARRAY_BUFFER, std::uint16_t>(_indices_vbo, indices, GL_STATIC_DRAW);
 
       OpenGL::Scoped::index_buffer_manual_binder indices_binder(_indices_vbo);
       OpenGL::Scoped::use_program shader(*_program.get());

src/noggit/rendering/Primitives.hpp

@@ -157,14 +157,20 @@ namespace Noggit::Rendering::Primitives
   class Line
   {
   public:
-      void draw(glm::mat4x4 const& mvp, std::vector<glm::vec3> const points, glm::vec4 const& color);
+      void initSpline();
+      void draw(glm::mat4x4 const& mvp, std::vector<glm::vec3> const points, glm::vec4 const& color, bool spline);
       void unload();
 
   private:
       bool _buffers_are_setup = false;
       void setup_buffers(std::vector<glm::vec3> const points);
+
+      void setup_buffers_interpolated(std::vector<glm::vec3> const points);
+      glm::vec3 interpolate(float t, glm::vec3 p0, glm::vec3 p1, glm::vec3 m0, glm::vec3 m1);
+
       int _indice_count = 0;
 
+      void setup_shader(std::vector<glm::vec3> vertices, std::vector<std::uint16_t> indices);
       OpenGL::Scoped::deferred_upload_vertex_arrays<1> _vao;
       OpenGL::Scoped::deferred_upload_buffers<2> _buffers;
       GLuint const& _vertices_vbo = _buffers[0];