Jump to content
  • Advertisement
Sign in to follow this  

OpenGL Fastest way to upload streaming points, and removing occasionally

This topic is 2163 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

So i have a system (using OpenGL 4.x) where i am receiving a stream of points (potentially with color and/or normal), from an external source. And I need to draw these points as GL_POINTS, running custom switchable shaders for coloring (color could be procedurally generated, or come from vertex color or normal direction).


The stream consists of receiving a group of points (with or without normal or color) of an arbitrary count (typical from 1k to 70k points) at a fairly regular interval, I need to add these points to my current points and draw all the points so far received points.


I am guaranteed that my vertex type will not change, I am told at the beginning of the streaming which to expect, so i am either using an interleaved vertex with: pos+normal+color, pos+normal, pos+color, or just pos.


My current solution is to allocate interleaved vertex VBOs (with surrounding VAOs) of the appropriate vertex type at a config file specified max vertex count (allocated with the DYNAMIC hint).


As new points come in i fill up my current non filled VBO via glBufferSubData. I keep a count (activePoints) of how many vertices the current frontier VBO has in it so far, and use glBufferSubData to fill in a range starting with activePoints, if my current update group has more vertices than can fit in my frontier buffer (since i limit the vertex count per VBO), then i allocate a new VBO and fill the range starting at 0 and ending with the number of points left in my update group (not added to the last buffer), if I still have points left I do this again and again. It is rare that an update group straddles more than 2 buffers.


When rendering i render all my VBOs (-1) with a glDrawArrays(m_DrawMode,0,numVertices), where numVertices is equal to max buffer allowed size, and my frontier buffer with a glDrawArrays(m_DrawMode,startElem,numElems) to account for it not being completely filled with valid vertices.


Of course at some point I will have more points than I can draw interactively, so i have an LRU mechanism that deallocates the oldest (according to the LRU alg) sets of VBOs as needed.


Is there a more optimal method for doing this? Buffer orphaning? Streaming hint? Map vs SubData? Something else?


The second issue is that i am now asked to removed points (at irregular intervals), ranging from 10 to 2000 at a time. But these points are irregularly spaced within the order I received them initially. I can find out what offsets in which buffers they currently exit in, but its more of a scattering than a range. I have been "removing them" by finding their offsets into the right buffers and one by one calling glBufferSubData with a range of 1 (its rare that they are beside each other in a buffer), and changing there pos to be somewhere far off where they will never be seen. Eventually i guess buffers should be deleted from these remove request adding up, but I don't currently do that.


What would be a better way to handle that?

Edited by Ender1618

Share this post

Link to post
Share on other sites
Sign in to follow this  

  • Advertisement

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

GameDev.net is your game development community. Create an account for your GameDev Portfolio and participate in the largest developer community in the games industry.

Sign me up!