Quiver Plot (Vector Field) Functionality.

implot.h

@@ -102,6 +102,7 @@ typedef int ImPlotStemsFlags;         // -> ImPlotStemsFlags_
 typedef int ImPlotInfLinesFlags;      // -> ImPlotInfLinesFlags_
 typedef int ImPlotPieChartFlags;      // -> ImPlotPieChartFlags_
 typedef int ImPlotHeatmapFlags;       // -> ImPlotHeatmapFlags_
+typedef int ImPlotQuiverFlags;        // -> ImPlotQuiverFlags_
 typedef int ImPlotHistogramFlags;     // -> ImPlotHistogramFlags_
 typedef int ImPlotDigitalFlags;       // -> ImPlotDigitalFlags_
 typedef int ImPlotImageFlags;         // -> ImPlotImageFlags_
@@ -309,6 +310,14 @@ enum ImPlotHeatmapFlags_ {
     ImPlotHeatmapFlags_ColMajor = 1 << 10, // data will be read in column major order
 };
 
+// Flags for PlotQuiver
+enum ImPlotQuiverFlags_ {
+    ImPlotQuiverFlags_None              = 0,         // default
+    ImPlotQuiverFlags_NoClip            = 1 << 10,   // arrows on the edge of a plot will not be clipped
+    ImPlotQuiverFlags_FixedSize         = 1 << 11,   // all arrows will have the same size
+    ImPlotQuiverFlags_ColorByMagnitude  = 1 << 12    // arrow colors will be mapped to their magnitudes
+};
+
 // Flags for PlotHistogram and PlotHistogram2D
 enum ImPlotHistogramFlags_ {
     ImPlotHistogramFlags_None       = 0,       // default
@@ -915,6 +924,9 @@ IMPLOT_TMP void PlotPieChart(const char* const label_ids[], const T* values, int
 // Plots a 2D heatmap chart. Values are expected to be in row-major order by default. Leave #scale_min and scale_max both at 0 for automatic color scaling, or set them to a predefined range. #label_fmt can be set to nullptr for no labels.
 IMPLOT_TMP void PlotHeatmap(const char* label_id, const T* values, int rows, int cols, double scale_min=0, double scale_max=0, const char* label_fmt="%.1f", const ImPlotPoint& bounds_min=ImPlotPoint(0,0), const ImPlotPoint& bounds_max=ImPlotPoint(1,1), ImPlotHeatmapFlags flags=0);
 
+// Plots a standard 2D quiver plot. The direction and magnitude of the arrows are determined by #us and #vs. Set #mag_min and #mag_max to specify a range of magnitudes to map to the arrow colors. Set mag_min = mag_max = 0 to use the full colormap range.
+IMPLOT_TMP void PlotQuiver(const char* label_id, const T* xs, const T* ys,const T* us, const T* vs, int count, double mag_min=0, double mag_max=0, ImPlotQuiverFlags flags=0, int offset=0, int stride=sizeof(T));
+
 // Plots a horizontal histogram. #bins can be a positive integer or an ImPlotBin_ method. If #range is left unspecified, the min/max of #values will be used as the range.
 // Otherwise, outlier values outside of the range are not binned. The largest bin count or density is returned.
 IMPLOT_TMP double PlotHistogram(const char* label_id, const T* values, int count, int bins=ImPlotBin_Sturges, double bar_scale=1.0, ImPlotRange range=ImPlotRange(), ImPlotHistogramFlags flags=0);
@@ -1142,6 +1154,8 @@ IMPLOT_API void SetNextFillStyle(const ImVec4& col = IMPLOT_AUTO_COL, float alph
 IMPLOT_API void SetNextMarkerStyle(ImPlotMarker marker = IMPLOT_AUTO, float size = IMPLOT_AUTO, const ImVec4& fill = IMPLOT_AUTO_COL, float weight = IMPLOT_AUTO, const ImVec4& outline = IMPLOT_AUTO_COL);
 // Set the error bar style for the next item only.
 IMPLOT_API void SetNextErrorBarStyle(const ImVec4& col = IMPLOT_AUTO_COL, float size = IMPLOT_AUTO, float weight = IMPLOT_AUTO);
+// Set the quiver style for the next item only.
+IMPLOT_API void SetNextQuiverStyle(float size, const ImVec4& col = IMPLOT_AUTO_COL);
 
 // Gets the last item primary color (i.e. its legend icon color)
 IMPLOT_API ImVec4 GetLastItemColor();

implot_demo.cpp

@@ -78,6 +78,16 @@ void StyleSeaborn();
 
 namespace ImPlot {
 
+static void HelpMarker(const char* desc) {
+    ImGui::TextDisabled("(?)");
+    if (ImGui::BeginItemTooltip()) {
+        ImGui::PushTextWrapPos(ImGui::GetFontSize() * 35.0f);
+        ImGui::TextUnformatted(desc);
+        ImGui::PopTextWrapPos();
+        ImGui::EndTooltip();
+    }
+}
+
 template <typename T>
 inline T RandomRange(T min, T max) {
     T scale = rand() / (T) RAND_MAX;
@@ -737,6 +747,75 @@ void Demo_Heatmaps() {
 
 //-----------------------------------------------------------------------------
 
+void Demo_QuiverPlots(){
+    static float xs[100], ys[100], us[100], vs[100];
+    for (int i = 0; i < 10; ++i) {
+        for(int j = 0; j < 10; ++j){
+            int idx = i*10 + j;
+            xs[idx] = ((float)j * 0.1f) - 0.5;
+            ys[idx] = ((float)i * 0.1f) - 0.5;
+
+            // Taylor-Green vortex
+            float k = 2.0f * 3.14159f;
+            us[idx] = sinf(k * xs[idx]) * cosf(k * ys[idx]);
+            vs[idx] = -cosf(k * xs[idx]) * sinf(k * ys[idx]);
+        }
+    }
+
+    static float mag_min = 0.00f;
+    static float mag_max = 1.0f;
+    static float base_size = 12.0f;
+    static ImPlotColormap map = ImPlotColormap_Viridis;
+
+    if (ImPlot::ColormapButton(ImPlot::GetColormapName(map), ImVec2(225,0), map)) {
+        map = (map + 1) % ImPlot::GetColormapCount();
+    }
+    ImGui::SameLine();
+    ImGui::LabelText("##Colormap Index", "%s", "Change Colormap");
+
+    ImGui::SetNextItemWidth(225);
+    ImGui::DragFloatRange2("Min / Max Magnitude", &mag_min, &mag_max, 0.01f, -20, 20,nullptr,nullptr,ImGuiSliderFlags_AlwaysClamp);
+    if (mag_max < mag_min) {
+        mag_max = mag_min;
+    }
+    ImGui::SameLine();
+    HelpMarker("Minumum and maximum magnitudes for color mapping");
+
+    ImGui::SetNextItemWidth(225);
+    ImGui::DragFloat("Base Size", &base_size, 0.1f, 0, 100);
+    ImGui::SameLine();
+    HelpMarker("Maximum arrow size in pixels. The actual size will depend on the arrow's magnitude");
+
+    static ImPlotQuiverFlags qv_flags = ImPlotQuiverFlags_ColorByMagnitude;
+
+    CHECKBOX_FLAG(qv_flags, ImPlotQuiverFlags_NoClip);
+    ImGui::SameLine();
+    HelpMarker("Arrows on the edge of the plot will not be clipped");
+
+    CHECKBOX_FLAG(qv_flags, ImPlotQuiverFlags_FixedSize);
+    ImGui::SameLine();
+    HelpMarker("All arrows will have the length set to base size");
+
+    CHECKBOX_FLAG(qv_flags, ImPlotQuiverFlags_ColorByMagnitude);
+    ImGui::SameLine();
+    HelpMarker("Arrow will be colored by on their magnitudes");
+
+    ImPlot::PushColormap(map);
+    if (ImPlot::BeginPlot("Quiver Plot", ImVec2(ImGui::GetTextLineHeight()*28, ImGui::GetTextLineHeight()*28))) {
+        ImPlot::SetupAxisTicks(ImAxis_X1, -0.5, 0.5, 11);
+        ImPlot::SetupAxisTicks(ImAxis_Y1, -0.5, 0.5, 11);
+        ImPlot::SetNextQuiverStyle(base_size, ImPlot::GetColormapColor(1));
+        ImPlot::SetupAxes("x", "y");
+        ImPlot::PlotQuiver("Magnitude", xs, ys, us, vs, 100, mag_min, mag_max, qv_flags);
+        ImPlot::EndPlot();
+    }
+    ImGui::SameLine();
+    ImPlot::ColormapScale("##QuiverScale", mag_min, mag_max);
+    ImPlot::PopColormap();
+}
+
+//-----------------------------------------------------------------------------
+
 void Demo_Histogram() {
     static ImPlotHistogramFlags hist_flags = ImPlotHistogramFlags_Density;
     static int  bins       = 50;
@@ -2286,6 +2365,7 @@ void ShowDemoWindow(bool* p_open) {
             DemoHeader("Infinite Lines", Demo_InfiniteLines);
             DemoHeader("Pie Charts", Demo_PieCharts);
             DemoHeader("Heatmaps", Demo_Heatmaps);
+            DemoHeader("Quiver Plots", Demo_QuiverPlots);
             DemoHeader("Histogram", Demo_Histogram);
             DemoHeader("Histogram 2D", Demo_Histogram2D);
             DemoHeader("Digital Plots", Demo_DigitalPlots);

implot_internal.h

@@ -1199,6 +1199,7 @@ struct ImPlotNextItemData {
     ImPlotMarker    Marker;
     float           MarkerSize;
     float           MarkerWeight;
+    float           QuiverSize;
     float           FillAlpha;
     float           ErrorBarSize;
     float           ErrorBarWeight;
@@ -1218,6 +1219,7 @@ struct ImPlotNextItemData {
         LineWeight    = MarkerSize = MarkerWeight = FillAlpha = ErrorBarSize = ErrorBarWeight = DigitalBitHeight = DigitalBitGap = IMPLOT_AUTO;
         Marker        = IMPLOT_AUTO;
         HasHidden     = Hidden = false;
+
     }
 };