View Full Version : Drawing multiple polygons with vertex buffer object

02-21-2016, 02:28 AM
I tried to create program in which I would draw multiple polygons here is fragment of what I have done:

GLuint VertexArrayID;
exampleof drawing triangle(I have more polygons, like circle, and so on..)

if (figure == RECTANGLE)
data[0][0] = px1; data[0][1] = py1;
data[1][0] = px2; data[1][1] = py1;
data[2][0] = px2; data[2][1] = py2;
data[3][0] = px1; data[3][1] = py2;
vertex_count = 4;
if (vertex_count > 0)
glGenBuffers(3, VertexArrayID);
glBindBuffer(GL_ARRAY_BUFFER, VertexArrayID[0]);
glBufferData(GL_ARRAY_BUFFER, 2 * sizeof(float), data, GL_STATIC_DRAW);
//GLfloat* data = (GLfloat*)glMapBuffer(GL_ARRAY_BUFFER, GL_READ_WRITE);

glVertexPointer(2, GL_FLOAT, 0, NULL);
glDrawArrays(GL_TRIANGLE_FAN, 0, vertex_count);
Now the point is that I want to: 1) create polygon 2) save this polygon ob buffer 3) create other polygon 4) save that polygon 5) and so..

I know that here I create N buffers:

glGenBuffers(N, VertexArrayID);
But I need to know how to save each polygon on each buffer, and then show it all on screen. I tried do use glBufferSubData, glMapBuffer, I have read many tutorials, but still I don't know how to do that.