Use map projection with geo line

scwx-qt/source/scwx/qt/gl/draw/draw_item.cpp

@@ -6,6 +6,7 @@
 #include <glm/glm.hpp>
 #include <glm/gtc/matrix_transform.hpp>
 #include <glm/gtc/type_ptr.hpp>
+#include <mbgl/util/constants.hpp>
 #pragma warning(pop)
 
 namespace scwx
@@ -46,6 +47,49 @@ void DrawItem::UseDefaultProjection(
       uMVPMatrixLocation, 1, GL_FALSE, glm::value_ptr(projection));
 }
 
+// TODO: Refactor to utility class
+static glm::vec2
+LatLongToScreenCoordinate(const QMapbox::Coordinate& coordinate)
+{
+   double latitude = std::clamp(
+      coordinate.first, -mbgl::util::LATITUDE_MAX, mbgl::util::LATITUDE_MAX);
+   glm::vec2 screen {
+      mbgl::util::LONGITUDE_MAX + coordinate.second,
+      -(mbgl::util::LONGITUDE_MAX -
+        mbgl::util::RAD2DEG *
+           std::log(std::tan(M_PI / 4.0 +
+                             latitude * M_PI / mbgl::util::DEGREES_MAX)))};
+   return screen;
+}
+
+void DrawItem::UseMapProjection(
+   const QMapbox::CustomLayerRenderParameters& params,
+   GLint                                       uMVPMatrixLocation,
+   GLint                                       uMapScreenCoordLocation)
+{
+   OpenGLFunctions& gl = p->gl_;
+
+   // TODO: Refactor to utility class
+   const float scale = std::pow(2.0, params.zoom) * 2.0f *
+                       mbgl::util::tileSize / mbgl::util::DEGREES_MAX;
+   const float xScale = scale / params.width;
+   const float yScale = scale / params.height;
+
+   glm::mat4 uMVPMatrix(1.0f);
+   uMVPMatrix = glm::scale(uMVPMatrix, glm::vec3(xScale, yScale, 1.0f));
+   uMVPMatrix = glm::rotate(uMVPMatrix,
+                            glm::radians<float>(params.bearing),
+                            glm::vec3(0.0f, 0.0f, 1.0f));
+
+   gl.glUniform2fv(uMapScreenCoordLocation,
+                   1,
+                   glm::value_ptr(LatLongToScreenCoordinate(
+                      {params.latitude, params.longitude})));
+
+   gl.glUniformMatrix4fv(
+      uMVPMatrixLocation, 1, GL_FALSE, glm::value_ptr(uMVPMatrix));
+}
+
 } // namespace draw
 } // namespace gl
 } // namespace qt

scwx-qt/source/scwx/qt/gl/draw/draw_item.hpp

@@ -34,6 +34,9 @@ public:
 protected:
    void UseDefaultProjection(const QMapbox::CustomLayerRenderParameters& params,
                              GLint uMVPMatrixLocation);
+   void UseMapProjection(const QMapbox::CustomLayerRenderParameters& params,
+                         GLint uMVPMatrixLocation,
+                         GLint uMapScreenCoordLocation);
 
 private:
    class Impl;

scwx-qt/source/scwx/qt/gl/draw/geo_line.cpp

@@ -36,6 +36,7 @@ public:
        modulateColor_ {std::nullopt},
        shaderProgram_ {nullptr},
        uMVPMatrixLocation_(GL_INVALID_INDEX),
+       uMapScreenCoordLocation_(GL_INVALID_INDEX),
        vao_ {GL_INVALID_INDEX},
        vbo_ {GL_INVALID_INDEX}
    {
@@ -57,6 +58,7 @@ public:
 
    std::shared_ptr<ShaderProgram> shaderProgram_;
    GLint                          uMVPMatrixLocation_;
+   GLint                          uMapScreenCoordLocation_;
 
    GLuint vao_;
    GLuint vbo_;
@@ -88,6 +90,13 @@ void GeoLine::Initialize()
       logger_->warn("Could not find uMVPMatrix");
    }
 
+   p->uMapScreenCoordLocation_ =
+      gl.glGetUniformLocation(p->shaderProgram_->id(), "uMapScreenCoord");
+   if (p->uMapScreenCoordLocation_ == -1)
+   {
+      logger_->warn("Could not find uMapScreenCoord");
+   }
+
    gl.glGenVertexArrays(1, &p->vao_);
    gl.glGenBuffers(1, &p->vbo_);
 
@@ -146,7 +155,8 @@ void GeoLine::Render(const QMapbox::CustomLayerRenderParameters& params)
 
       p->Update();
       p->shaderProgram_->Use();
-      UseDefaultProjection(params, p->uMVPMatrixLocation_);
+      UseMapProjection(
+         params, p->uMVPMatrixLocation_, p->uMapScreenCoordLocation_);
 
       // Draw line
       gl.glDrawArrays(GL_TRIANGLES, 0, 6);