Adding custom offset and scaling for color table to fragment shader

scwx-qt/gl/radar.frag

@@ -4,6 +4,8 @@
 precision mediump float;
 
 uniform sampler1D uTexture;
+uniform uint uDataMomentOffset;
+uniform float uDataMomentScale;
 
 flat in uint dataMoment;
 
@@ -11,7 +13,7 @@ layout (location = 0) out vec4 fragColor;
 
 void main()
 {
-   float texCoord = float(dataMoment - 2u) / 253.0f; // TODO: Scale properly
+   float texCoord = float(dataMoment - uDataMomentOffset) / uDataMomentScale;
 
    fragColor = texture(uTexture, texCoord);
 }

scwx-qt/source/scwx/qt/map/radar_product_layer.cpp

@@ -53,6 +53,8 @@ public:
    gl::ShaderProgram     shaderProgram_;
    GLint                 uMVPMatrixLocation_;
    GLint                 uMapScreenCoordLocation_;
+   GLint                 uDataMomentOffsetLocation_;
+   GLint                 uDataMomentScaleLocation_;
    std::array<GLuint, 2> vbo_;
    GLuint                vao_;
    GLuint                texture_;
@@ -95,6 +97,24 @@ void RadarProductLayer::initialize()
          << logPrefix_ << "Could not find uMapScreenCoord";
    }
 
+   p->uDataMomentOffsetLocation_ =
+      gl.glGetUniformLocation(p->shaderProgram_.id(), "uDataMomentOffset");
+   if (p->uDataMomentOffsetLocation_ == -1)
+   {
+      BOOST_LOG_TRIVIAL(warning)
+         << logPrefix_ << "Could not find uDataMomentOffset";
+   }
+
+   p->uDataMomentScaleLocation_ =
+      gl.glGetUniformLocation(p->shaderProgram_.id(), "uDataMomentScale");
+   if (p->uDataMomentScaleLocation_ == -1)
+   {
+      BOOST_LOG_TRIVIAL(warning)
+         << logPrefix_ << "Could not find uDataMomentScale";
+   }
+
+   p->shaderProgram_.Use();
+
    // Generate a vertex array object
    gl.glGenVertexArrays(1, &p->vao_);
 
@@ -187,6 +207,8 @@ void RadarProductLayer::render(
 {
    gl::OpenGLFunctions& gl = p->gl_;
 
+   p->shaderProgram_.Use();
+
    if (p->colorTableNeedsUpdate_)
    {
       UpdateColorTable();
@@ -197,8 +219,6 @@ void RadarProductLayer::render(
       UpdateSweep();
    }
 
-   p->shaderProgram_.Use();
-
    const float scale = std::pow(2.0, params.zoom) * 2.0f *
                        mbgl::util::tileSize / mbgl::util::DEGREES_MAX;
    const float xScale = scale / params.width;
@@ -252,12 +272,18 @@ void RadarProductLayer::UpdateColorTable()
 {
    BOOST_LOG_TRIVIAL(debug) << logPrefix_ << "UpdateColorTable()";
 
+   uint16_t rangeMin;
+   uint16_t rangeMax;
+   float    scale;
+
    p->colorTableNeedsUpdate_ = false;
 
    gl::OpenGLFunctions& gl = p->gl_;
 
    const std::vector<boost::gil::rgba8_pixel_t>& colorTable =
-      p->radarProductView_->color_table();
+      p->radarProductView_->color_table(rangeMin, rangeMax);
+
+   scale = rangeMax - rangeMin;
 
    gl.glActiveTexture(GL_TEXTURE0);
    gl.glBindTexture(GL_TEXTURE_1D, p->texture_);
@@ -270,6 +296,9 @@ void RadarProductLayer::UpdateColorTable()
                    GL_UNSIGNED_BYTE,
                    colorTable.data());
    gl.glGenerateMipmap(GL_TEXTURE_1D);
+
+   gl.glUniform1ui(p->uDataMomentOffsetLocation_, rangeMin);
+   gl.glUniform1f(p->uDataMomentScaleLocation_, rangeMax - rangeMin);
 }
 
 void RadarProductLayer::UpdateColorTableNextFrame()

scwx-qt/source/scwx/qt/view/level2_product_view.cpp

@@ -47,7 +47,9 @@ public:
        longitude_ {},
        sweepTime_ {},
        colorTable_ {},
-       colorTableLut_ {}
+       colorTableLut_ {},
+       colorTableMin_ {2},
+       colorTableMax_ {254}
    {
       auto it = blockTypes_.find(product);
 
@@ -81,6 +83,8 @@ public:
 
    std::shared_ptr<common::ColorTable>    colorTable_;
    std::vector<boost::gil::rgba8_pixel_t> colorTableLut_;
+   uint16_t                               colorTableMin_;
+   uint16_t                               colorTableMax_;
 
    std::shared_ptr<common::ColorTable> savedColorTable_;
    float                               savedScale_;
@@ -100,14 +104,16 @@ Level2ProductView::Level2ProductView(
 Level2ProductView::~Level2ProductView() = default;
 
 const std::vector<boost::gil::rgba8_pixel_t>&
-Level2ProductView::color_table() const
+Level2ProductView::color_table(uint16_t& minValue, uint16_t& maxValue) const
 {
    if (p->colorTableLut_.size() == 0)
    {
-      return RadarProductView::color_table();
+      return RadarProductView::color_table(minValue, maxValue);
    }
    else
    {
+      minValue = p->colorTableMin_;
+      maxValue = p->colorTableMax_;
       return p->colorTableLut_;
    }
 }
@@ -216,6 +222,9 @@ void Level2ProductView::UpdateColorTable()
                     lut[i - *dataRange.begin()] = p->colorTable_->Color(f);
                  });
 
+   p->colorTableMin_ = rangeMin;
+   p->colorTableMax_ = rangeMax;
+
    p->savedColorTable_ = p->colorTable_;
    p->savedOffset_     = offset;
    p->savedScale_      = scale;

scwx-qt/source/scwx/qt/view/level2_product_view.hpp

@@ -28,7 +28,8 @@ public:
       std::shared_ptr<manager::RadarProductManager> radarProductManager);
    ~Level2ProductView();
 
-   const std::vector<boost::gil::rgba8_pixel_t>& color_table() const override;
+   const std::vector<boost::gil::rgba8_pixel_t>&
+   color_table(uint16_t& minValue, uint16_t& maxValue) const override;
    std::chrono::system_clock::time_point sweep_time() const override;
    const std::vector<float>&             vertices() const override;
 

scwx-qt/source/scwx/qt/view/radar_product_view.cpp

@@ -18,6 +18,8 @@ static const std::vector<boost::gil::rgba8_pixel_t> DEFAULT_COLOR_TABLE = {
    boost::gil::rgba8_pixel_t(0, 128, 0, 255),
    boost::gil::rgba8_pixel_t(255, 192, 0, 255),
    boost::gil::rgba8_pixel_t(255, 0, 0, 255)};
+static const uint16_t DEFAULT_COLOR_TABLE_MIN = 2u;
+static const uint16_t DEFAULT_COLOR_TABLE_MAX = 255u;
 
 class RadarProductViewImpl
 {
@@ -31,8 +33,10 @@ RadarProductView::RadarProductView() :
 RadarProductView::~RadarProductView() = default;
 
 const std::vector<boost::gil::rgba8_pixel_t>&
-RadarProductView::color_table() const
+RadarProductView::color_table(uint16_t& minValue, uint16_t& maxValue) const
 {
+   minValue = DEFAULT_COLOR_TABLE_MIN;
+   maxValue = DEFAULT_COLOR_TABLE_MAX;
    return DEFAULT_COLOR_TABLE;
 }
 

scwx-qt/source/scwx/qt/view/radar_product_view.hpp

@@ -25,7 +25,8 @@ public:
    explicit RadarProductView();
    ~RadarProductView();
 
-   virtual const std::vector<boost::gil::rgba8_pixel_t>& color_table() const;
+   virtual const std::vector<boost::gil::rgba8_pixel_t>&
+   color_table(uint16_t& minValue, uint16_t& maxValue) const;
    virtual std::chrono::system_clock::time_point sweep_time() const;
    virtual const std::vector<float>&             vertices() const = 0;