如何使用OpenGL和GLSL更改颜色（C ++）？

Question

I am working on an OpenGL project in C++, and I want to learn how to use GLSL shaders. The problem is that, while I can complete my program without using my own shaders, I want to write my own (at this time there are no shaders that I load myself - not sure if OpenGL defaults any).

To draw a bunch of lines on the image (whose vertices are stored in a vector and color values are stored in another vector), I use the following code to run through and render them whenever the frame is updated - I use the GLUT display function for this.

glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_LINES);  
vector<point2>::iterator it;
int c_index = 0;
for(it=points.begin(); it<points.end(); it++){
    if(c_index % 2 == 0) //set color for every pair of points (each line)
        glColor3f(colors[c_index/2][0], colors[c_index/2][1], colors[c_index/2][2]);
    c_index++;

    glVertex2f(it->x, it->y); //set vertex
}
glEnd();
glFlush();

Now, the problem is when I try to use shaders that I found in another example program, the color is all red (even though the shaders do not explicitly define any colors). It also makes glColor3f do nothing.

My question is, assuming I can use shaders to do this, what do the shaders have to look like, and how would I load them?

Answer 1

Apparently it cannot be done using glColor3f. Instead, I had to make a pre-determined OpenGL buffer, and send the buffer data to the shaders. It can't be done "on the fly" as I hoped.