1 files changed, 90 insertions, 0 deletions
diff --git a/extension/src/Utilities.cpp b/extension/src/Utilities.cpp
index a912490..f09eae0 100644
--- a/extension/src/Utilities.cpp
+++ b/extension/src/Utilities.cpp
@@ -1,5 +1,7 @@
 #include "Utilities.hpp"
 
+#include <numbers>
+
 #include <godot_cpp/classes/resource_loader.hpp>
 #include <godot_cpp/variant/utility_functions.hpp>
 
@@ -14,3 +16,91 @@ Ref<Image> OpenVic::load_godot_image(String const& path) {
 		return Image::load_from_file(path);
 	}
 }
+
+// Get the polar coordinates of a pixel relative to the center
+static Vector2 getPolar(Vector2 UVin, Vector2 center) {
+	Vector2 relcoord = (UVin-center);
+	float dist = relcoord.length();
+	float theta = std::numbers::pi / 2 + atan2(relcoord.y, relcoord.x);
+	if (theta < 0.0f) theta += std::numbers::pi * 2;
+	return { dist, theta };
+}
+
+// From thebookofshaders, returns a gradient falloff
+static inline float parabola(float base, float x, float k){
+	return powf(base * x * (1.0 - x), k);
+}
+
+static inline float parabola_shadow(float base, float x){
+	return base * x * x;
+}
+
+static Color pie_chart_fragment(Vector2 UV, float radius, Array const& stopAngles, Array const& colours,
+	Vector2 shadow_displacement, float shadow_tightness, float shadow_radius, float shadow_thickness,
+	Color trim_colour, float trim_size, float gradient_falloff, float gradient_base,
+	bool donut, bool donut_inner_trim, float donut_inner_radius) {
+
+	Vector2 coords = getPolar(UV, { 0.5, 0.5 });
+	float dist = coords.x;
+	float theta = coords.y;
+
+	Vector2 shadow_polar = getPolar(UV, shadow_displacement);
+	float shadow_peak = radius + (radius - donut_inner_radius) / 2.0;
+	float shadow_gradient = shadow_thickness + parabola_shadow(shadow_tightness * -10.0, shadow_polar.x + shadow_peak - shadow_radius);
+
+	// Inner hole of the donut => make it transparent
+	if (donut && dist <= donut_inner_radius) {
+		return { 0.1, 0.1, 0.1, shadow_gradient };
+	}
+	// Inner trim
+	else if (donut && donut_inner_trim && dist <= donut_inner_radius + trim_size) {
+		return { trim_colour, 1.0 };
+	}
+	// Interior
+	else if (dist <= radius-trim_size) {
+		Color col { 1.0f, 0.0f, 0.0f };
+		for (int i = 0; i < stopAngles.size(); i++){
+			if (theta <= float(stopAngles[i])) {
+				col = colours[i];
+				break;
+			}
+		}
+		float gradient = parabola(gradient_base, dist, gradient_falloff);
+		return { col * (1.0 - gradient), 1.0 };
+	}
+	// Outer trim
+	else if (dist <= radius) {
+		return { trim_colour, 1.0 };
+	}
+	// Outside the circle
+	else{
+		return { 0.1, 0.1, 0.1, shadow_gradient };
+	}
+}
+
+void OpenVic::draw_pie_chart(Ref<Image> image,
+	Array const& stopAngles, Array const& colours, float radius,
+	Vector2 shadow_displacement, float shadow_tightness, float shadow_radius, float shadow_thickness,
+	Color trim_colour, float trim_size, float gradient_falloff, float gradient_base,
+	bool donut, bool donut_inner_trim, float donut_inner_radius) {
+
+	ERR_FAIL_NULL_EDMSG(image, "Cannot draw pie chart to null image.");
+	const int32_t width = image->get_width();
+	const int32_t height = image->get_height();
+	ERR_FAIL_COND_EDMSG(width <= 0 || height <= 0, "Cannot draw pie chart to empty image.");
+	if (width != height) {
+		UtilityFunctions::push_warning("Drawing pie chart to non-square image: ", width, "x", height);
+	}
+	const int32_t size = std::min(width, height);
+	for (int32_t y = 0; y < size; ++y) {
+		for (int32_t x = 0; x < size; ++x) {
+			image->set_pixel(x, y, pie_chart_fragment(
+				{ static_cast<float>(x) / static_cast<float>(size),
+				  static_cast<float>(y) / static_cast<float>(size) },
+				radius, stopAngles, colours,
+				shadow_displacement, shadow_tightness, shadow_radius, shadow_thickness,
+				trim_colour, trim_size, gradient_falloff, gradient_base,
+				donut, donut_inner_trim, donut_inner_radius));
+		}
+	}
+}