+ VBO by default

+ some error-handling
+ transparency

main.cpp

@@ -30,7 +30,9 @@ bool TestGame::init()
     cerr << "Could not bind attribute " << attribute_name << endl;
     throw nullptr;
   }
-  
+  t1.init();
+  t2.init();
+  t3.init();
   return true;
 }
 void TestGame::stop()
@@ -52,7 +54,8 @@ void TestGame::render()
   //Clear Background
   glClearColor(1.0, 1.0, 1.0, 1.0);
   glClear(GL_COLOR_BUFFER_BIT);
-  
+  glEnable(GL_BLEND);
+  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
   glUseProgram(program);
   glEnableVertexAttribArray(attribute_coord2d);
 

renderer/main.cpp

@@ -6,7 +6,16 @@ MainClass::MainClass(int width, int height)
 {
   SDL_Init(SDL_INIT_VIDEO);
   window = SDL_CreateWindow("Testgame", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, width, height, SDL_WINDOW_RESIZABLE | SDL_WINDOW_OPENGL);
-  SDL_GL_CreateContext(window);
+  if(!window) {
+    cerr << "Error: can't create window: " << SDL_GetError() << endl;
+    throw nullptr;
+  }
+  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
+  SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 1);
+  if(!SDL_GL_CreateContext(window)) {
+    cerr << "Error: SDL_GL_CreateContext: " << SDL_GetError() << endl;
+    throw nullptr;
+  }
 }
 void MainClass::start()
 {

renderer/shapes/triangle.cpp

@@ -13,20 +13,27 @@ Triangle::Triangle(float ax, float ay, float bx, float by, float cx, float cy)
   B.y=by-1.0;
   C.x=cx-1.0;
   C.y=cy-1.0;
-}
-
-Triangle::~Triangle()
-{
   
 }
-bool Triangle::render(GLint attrib)
-{
+auto Triangle::init() -> void {
   GLfloat triangle_vertices[] = {
     A.x, A.y,
     B.x, B.y,
     C.x, C.y
   };
-  glVertexAttribPointer(attrib, 2, GL_FLOAT, GL_FALSE, 0, triangle_vertices);
+  glGenBuffers(1, &vbo_triangle);
+  glBindBuffer(GL_ARRAY_BUFFER, vbo_triangle); //Create VBO
+  //Fill VBO
+  glBufferData(GL_ARRAY_BUFFER, sizeof(triangle_vertices), triangle_vertices, GL_STATIC_DRAW);
+}
+Triangle::~Triangle()
+{
+  glDeleteBuffers(1, &vbo_triangle);
+}
+bool Triangle::render(GLint attrib)
+{
+  glBindBuffer(GL_ARRAY_BUFFER, vbo_triangle);
+  glVertexAttribPointer(attrib, 2, GL_FLOAT, GL_FALSE, 0, 0);
   glDrawArrays(GL_TRIANGLES, 0, 3);
   return true;
 }

renderer/shapes/triangle.h

@@ -4,6 +4,7 @@
 #include <renderer/shapes/float2D.h>
 class Triangle {
 private:
+  GLuint vbo_triangle;
   float2D A;
   float2D B;
   float2D C; //The three points
@@ -11,6 +12,7 @@ public:
   Triangle(float x, float y, float alen, float blen, float clen);
   Triangle(float ax, float ay, float bx, float by, float cx, float cy);
   ~Triangle();
+  auto init() -> void;
   auto render(GLint attrib) -> bool;
 };
 #endif

shaders/triangle.f.glsl

@@ -2,4 +2,5 @@ void main(void) {
   gl_FragColor[0] = 1.0;
   gl_FragColor[1] = 1.0;
   gl_FragColor[2] = 0.0;
+  gl_FragColor[3] = floor(mod(gl_FragCoord.y, 3.0));
 }