added vector fields

src/VectorField.cpp

@@ -0,0 +1,64 @@
+#include "VectorField.hpp"
+
+#include <SDL.h>
+
+VectorField::VectorField() :
+	width(0), height(0), biggestMagnitude(1.0)
+{
+}
+
+VectorField::VectorField(int width, int height) :
+	width(width), height(height)
+{
+	horizontal	= std::vector<double>(width * height, 0.0);
+	vertical	= std::vector<double>(width * height, 0.0);
+
+	biggestMagnitude = 1.0f;
+}
+
+VectorField::VectorField(int width, int height, const std::vector<double>& hori, const std::vector<double>& vert) :
+	width(width), height(height)
+{
+	horizontal = hori;
+	vertical = vert;
+
+	for (double u : horizontal)
+	{
+		for (double v : vertical)
+		{
+			biggestMagnitude = std::max(biggestMagnitude, u * u + v * v);
+		}
+	}
+
+	if (biggestMagnitude == 0.0)	// should use an epsilon probably
+		biggestMagnitude = 1.0;
+
+	biggestMagnitude = sqrt(biggestMagnitude);
+}
+
+void VectorField::Draw(SDL_Renderer* renderer, const SDL_Rect& targetRect)
+{
+	double cellWidth = (double)(targetRect.w - targetRect.x) / (double)width;
+	double cellHeight = (double)(targetRect.h - targetRect.y) / (double)height;
+
+	SDL_FRect vectorCenterSquare;
+	vectorCenterSquare.w = cellWidth / 5.0;
+	vectorCenterSquare.h = cellHeight / 5.0;
+
+	SDL_SetRenderDrawColor(renderer, 200, 20, 20, 255);
+	for (int y = 0; y < height; y++)
+	{
+		for (int x = 0; x < width; x++)
+		{
+			vectorCenterSquare.x = (double)targetRect.x + cellWidth * (x + 0.4);	// cellWidth * x + cellWidth / 2 - cellWidth / 10
+			vectorCenterSquare.y = (double)targetRect.y + cellHeight * (y + 0.4);
+			SDL_RenderFillRectF(renderer, &vectorCenterSquare);
+			SDL_RenderDrawLineF(renderer,
+				(double)targetRect.x + cellWidth * (x + 0.5),
+				(double)targetRect.y + cellHeight * (y + 0.5),
+				(double)targetRect.x + cellWidth * (x + 0.5) + horizontal[y * width + x] / biggestMagnitude * cellWidth,
+				(double)targetRect.y + cellHeight * (y + 0.5) + vertical[y * width + x] / biggestMagnitude * cellHeight
+			);
+		}
+	}
+}