computeShaderParticlesExample

Learning Objectives

This example demonstrates how to use a compute shader to set up an animated point cloud with editable parameters. Compute shaders are rather used to do generic computation in contrast to graphics-oriented shaders. In this case the shader computes the movement of particles using a flocking algorithm based on three parameters: attraction, cohesion and repulsion. It additionally includes different forces in order to separate the particles into groups.

You will learn how to..

• write a shader that animates particles according to their attraction, cohesion or repulsion
• create lively animations using ofNoise()
• use ofParameter objects and ofxGui to create editable variables
• connect parameters to a shader
• set a blend mode
• easily navigate in 3D with ofEasyCam

In the code, pay attention to:

• the separation of two particle groups by their gl_GlobalInvocationID
• the double buffer (ofBufferObject) for faster computation that allows to draw from one buffer while the other one is being updated
• the definition of working groups by setting dispatchCompute() from the C++ shader object and layout() from within the shader

Expected Behavior

When launching this app, you should see a cloud of particles floating in the center of a white cube. In the top left corner there is a panel to manipulate the particle cloud. The panel also includes a display of the current framerate.

Instructions for use:

• Use the mouse to adjust the interactive camera
  • Left click drag = orbit the target
  • Right click drag = dolly in and out
  • Double click = reset camera position
• Change the parameters in the panel to manipulate the particle cloud, for example..
  • check "dir as color" to show each particle in a color according to the direction it is heading
  • change attr1_force to adjust the force applied to all particles with an odd index
  • change attr2_force to adjust the force applied to all particles with an even index

Other classes used in this file

This Example uses the following classes:

• ofShader
• ofVbo
• ofBufferObject
• ofEasyCam
• ofParameter
• ofParameterGroup
• ofxPanel