Updating vertex data in a VBO (glBufferSubData vs glMapBuffer)

opengl vertex-buffer
Mark Ingram picture Mark Ingram · Sep 3, 2012 · Viewed 12.4k times · Source

I want to update an object's list of vertices after a VBO has been created. I've seen both glBufferSubData and glMapBuffer and they both appear to do similar things, which means I'm now unsure which one to use.

My pseudo workflow is:

Create object
Begin vertex update (calls glBufferData with data = nullptr)
Update object's vertices
End vertex update (takes the updated vertices and either calls glBufferSubData or glMapBuffer)

Answer

Calvin1602 picture Calvin1602 · Sep 3, 2012

Both work.

If you intend to update the vertices often (every frame or so), I recommend avoiding glBufferSubData, which requires one more memcpy in the driver. glMapBuffer/glMapBufferRange usually gets you more perf.

If you update only rarely, glBufferSubData will do fine.

See also chapter 28 of OpenGL Insights ( free : http://openglinsights.com/ )

Related questions

When are VBOs faster than "simple" OpenGL primitives (glBegin())?

After many years of hearing about Vertex Buffer Objects (VBOs), I finally decided to experiment with them (my stuff isn't normally performance critical, obviously...) I'll describe my experiment below, but to make a long story short, I'm seeing indistinguishable performance …

Read More
OpenGL. Updating vertex buffer with glBufferData

I'm using OpenGL to implement some kind of batched drawing. For this I create a vertex buffer to store data. Note: this buffer generally will update on each frame, but will never decrease size (but still can increase). My question …

Read More
Hard time understanding indices with glDrawElements

I'm trying to draw a terrain with GL_TRIANGLE_STRIP and glDrawElements but I'm having a really hard time understanding the indices thing behind glDrawElements... Here's what I have so far: void Terrain::GenerateVertexBufferObjects(float ox, float oy, float oz) { …

Read More