Constructing a ladder

Question

Let's start with a basic OpenGL ES 2.0 setup (like the Xcode OpenGL game template), If I want to add parts (vertices I should say?) to my model over time, what should I do!

To clarify, let's say I want to add a "step" to a ladder every 5 seconds or every time user taps the view, I initialize with one "step" like an elongated cube and then as things are being rendered on the screen I want to "add" vertices to my data buffer (?),

can I just call:

glBufferData(GL_ARRAY_BUFFER, sizeof(gCubeVertexData), gCubeVertexData, GL_STATIC_DRAW);

with a brand new gCubeVertexData array of floats on the fly each time?
What is the best approach to this?

Answer 1

Note that that way you would need a buffer for every ladder in your game. And even if you have only one ladder you will have to reset the mesh whenever it you want to display it with less steps. Based on that I think in this case the best wouldn't be to modify the mesh but rather to draw the parts the ladder is consisting of each on their own.

Example:

ladderBase.drawScaled(1, ladderLength);
for(int i=0; i++; i<ladderLength)
   ladderStep.drawAtPosition(0, i);

However if for any reason you really want to modify the mesh on run time note that you can use glBufferSubData to update only a part of the buffer, as opposed to replace the whole old data with the whole new data.