Fixed vertical axis label bug, more screenshots.

README.md

@@ -1,6 +1,6 @@
 # SdlGrapher
 SdlGrapher is a small program to render math functions as Charts built with SDL2 library.
-It's goal is also to demonstrate **floating-point precision errors**, that's why i didn't do any border / scaling checks.
+The goal is also to demonstrate **floating-point precision errors**, that's why i didn't do any border / scaling checks.
 
 ## Features
 * Horizontal / vertical scrolling.
@@ -10,7 +10,18 @@ It's goal is also to demonstrate **floating-point precision errors**, that's why
 * Automatically calculate scale and axis position based on interval of the math function.
 * Pixel perfect rendering.
 
-## Demo
-![Sin demo](/screenshots/sin.png)
+## Screenshots
+#### f(x) = x ^ 2
+![Parabola demo](/screenshots/xx.png)
+#### f(x) = 1 / x
+![Log demo](/screenshots/1divx.png)
+#### f(x) = log(x)
 ![Log demo](/screenshots/log.png)
+#### f(x) = sqrt(x)
+![Log demo](/screenshots/sqrt.png)
+#### f(x) = sin(x)
+![Sin demo](/screenshots/sin.png)
+#### f(x) = sqrt(x) * sin(x)
+![Sin demo](/screenshots/sqrtsin.png)
+#### f(x) = 3 * sin(x / 4) - 2 / sin(2 * x)
 ![Sin2 demo](/screenshots/sin2.png)

main.cpp

@@ -9,12 +9,26 @@ double mathF(double x) {
 
     // return 1 / x;
 
+    /*if (x < 0.001) {
+        return std::numeric_limits<double>::quiet_NaN();
+    }*/
+
     /*if (x < 0.001) {
         return std::numeric_limits<double>::quiet_NaN();
     }
 
     return log(x);*/
 
+    // return x * x;
+    // return sin(x) / cos(x);
+    // return sin(x) * cos(x);
+    // return sin(x) + cos(x);
+    // return sin(x) - cos(x);
+    // return 13 * x;
+    // return sqrt(x);
+    // return sqrt(x) * sin(x);
+    // return x*x*sin(x);
+    // return 1 / x;
     // return sin(x);
     // return cos(x);
 

src/Grapher.c++

@@ -80,8 +80,12 @@ void Grapher::renderAxes() {
     // vertical line
     SDL_RenderDrawLine(renderer, cx, 0, cx, vHeight);
 
-    int fromY = (int)floor(screenYToMathY(0));
-    int toY = (int)floor(screenYToMathY(vHeight));
+    // int fromY = (int)floor(screenYToMathY(0));
+    // int toY = (int)ceil(screenYToMathY(vHeight));
+    int fromY = (int)floor(screenYToMathY(vHeight));
+    int toY = (int)ceil(screenYToMathY(0));
+
+    // std::cout << fromY << " " << toY << std::endl;
 
     while (fromY <= toY) {
 

src/Grapher.h

@@ -43,7 +43,7 @@ class Grapher : public App {
 
     double screenYToMathY(int screenY) {
 
-        return (screenY - cy) / scale;
+        return -(screenY - cy) / scale;
 
     }