OpenGL buffer woes - c++

Question

I've been getting back into OpenGL recently after transitioning to linux. For some reason or another, things like glGenBuffers, glBindBuffer, etc, aren't present with the normal GL headers, and cause my program to crash using GLEW. To get around this I've been using GLES2.
And now the problem:
#include <SFML/Graphics.hpp>
#include <GLES2/gl2.h>
#include <GL/gl.h>
int main() {
sf::RenderWindow window(sf::VideoMode(640, 480), "OpenGL Tests");
glOrtho(0, 640, 0, 480, -1, 1);
glEnable(GL_TEXTURE_2D);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_BLEND);
glClearColor(0, 0, 0, 0);
//x, y, r, g, b
GLfloat triangleVertices[15] = {
10, 10, 1, 0, 0,
110, 10, 0, 1, 0,
60, 96.6f, 0, 0, 1
};
GLuint triangleBuf;
glGenBuffers(1, &triangleBuf);
glBindBuffer(GL_VERTEX_ARRAY, triangleBuf);
glBufferData(GL_VERTEX_ARRAY, sizeof(triangleVertices), triangleVertices, GL_STATIC_DRAW);
glBindBuffer(GL_VERTEX_ARRAY, 0);
while(window.isOpen()) {
sf::Event event;
while(window.pollEvent(event)) {
if(event.type == sf::Event::Closed) window.close();
}
glClear(GL_COLOR_BUFFER_BIT);
glBindBuffer(GL_VERTEX_ARRAY, triangleBuf);
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(2, GL_FLOAT, 3, 0);
glEnableClientState(GL_COLOR_ARRAY);
glColorPointer(3, GL_FLOAT, 2, (GLfloat*) 2);
glDrawArrays(GL_TRIANGLES, 0, 3);
window.display();
sf::sleep(sf::milliseconds(50));
}
glDeleteBuffers(1, &triangleBuf);
}
This is how I remember using buffers, though to be honest I don't trust my memory. With good reason it seems, since this crashes immediately after the window opens.
I've tried changing the last argument to glDrawArrays to 1 instead of 3. I've also tried binding the buffer twice, first as GL_VERTEX_ARRAY, followed by glVertexPointer, second as GL_COLOR_ARRAY, followed by glColorPointer. No dice.

Answer 1

The 3rd parameter of glVertexPointer respectively glColorPointer is the byte offset between consecutive (stride). If a named buffer object is bound, then the 4th parameter is treated as a byte offset, too.
The stride parameter has to be 5 * sizeof(GLfloat), because each attribute tuple consists of 5 (GLfloat) components (X, Y, R, G, B). The offset for the vertex coordinates is 0, because they are at the beginning. The offset for the color is 2 * sizeof(GLfloat), because the color comes after the 2 components of the vertex coordinate.
Further more GL_VERTEX_ARRAY is not a valid buffer target. The buffer target for vertex attributes is GL_ARRAY_BUFFER. The wrong usage of GL_VERTEX_ARRAY will cause INVALID_ENUM errors. Error information can be get by glGetError.
Do the following changes:
glGenBuffers(1, &triangleBuf);
glBindBuffer(GL_ARRAY_BUFFER, triangleBuf);
glBufferData(GL_ARRAY_BUFFER, sizeof(triangleVertices), triangleVertices, GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindBuffer(GL_ARRAY_BUFFER, triangleBuf);
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(2, GL_FLOAT, 5*sizeof(GLfloat), 0);
glEnableClientState(GL_COLOR_ARRAY);
glColorPointer(3, GL_FLOAT, 5*sizeof(GLfloat), (GLfloat*)(2*sizeof(GLfloat)));
Since you do not bind a texture and you do net even have specified texture coordinates, do not enable 2 dimensional texturing:
glEnable(GL_TEXTURE_2D);