CODEWITHSUNDEEP
opengl
bluePhlavio
bluePhlavio

Reputation: 547

Draw particles trajectories of undefined length with opengl

I have to draw a physical simulation that displays trajectories of moving around particles. 3D position data are read from a database in realtime while drawing. Once set up a VBO for each object, the drawing call will be the standard glDrawArrays(GL_LINE_STRIP, 0, size). The problem is that VBOs storing trail points are updated every frame since new points are added. This seems to me extremely inefficient! Furthermore what if I want to draw the trajectories with a gradient color from the particle's actual position to the older points? I have to update the color of all vertices in the VBO at every draw call! What is the standard way through this kind of stuff?

To summarize:

I read many tutorials but I haven't found nothing about drawing ever-updating and indefinitely-growing lines... I will appreciate any suggestion! Thanks!

Upvotes: 1

Views: 176

Answers (1)

genpfault
genpfault

Reputation: 52083

  1. Use multiple VBOs so that you have a fixed number of vertices per. That way you only have to modify the last VBO in the sequence when you add new points instead of completely updating one giant VBO.
  2. Add a sequence number vertex attribute or use gl_VertexID and pass in the total point count as a uniform. Then you can divide a given vertex's sequence number by the total count and use that fraction to mix between your gradient colors.

Upvotes: 1

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