Accessing Point Positions in Shaders

In a Three.js/React Three Fiber point cloud setup, the shader does have access to each individual point's position through the vertex shader. Here's how it works:

How Shaders Access Point Positions

When you create a point cloud with a custom shader material:

1. The attributes-position buffer attribute you've defined contains the local positions of each point
2. In your vertex shader, these positions are accessible through the built-in position attribute
3. The global/world position is calculated by applying the model-view-projection matrices to this position

Implementation Approach

To properly access and manipulate point positions in your shader:

1. Define your vertex shader to receive the position attribute
2. Use uniforms to pass animation parameters
3. Calculate the world position in the vertex shader

Here's how to modify your code:

JAVASCRIPTCopied
const BrainParticleMaterial = shaderMaterial(
  {
    // Uniforms for animation
    time: 0,
    // Add any other animation parameters you need
  },
  // Vertex Shader
  `
    attribute vec3 position;
    attribute float randoms;
    
    uniform float time;
    // Add other uniforms as needed
    
    varying vec3 vPosition; // To pass to fragment shader if needed
    
    void main() {
      // Access the local position directly via 'position'
      vec3 pos = position;
      
      // Apply any animations or transformations here
      // Example: pos.y += sin(time + randoms) * 0.1;
      
      // Calculate the final position
      vec4 worldPosition = modelMatrix * vec4(pos, 1.0);
      vec4 viewPosition = viewMatrix * worldPosition;
      gl_Position = projectionMatrix * viewPosition;
      
      // Pass the world position to fragment shader if needed
      vPosition = worldPosition.xyz;
      
      // Set point size (optional)
      gl_PointSize = 2.0;
    }
  `,
  // Fragment Shader
  `
    varying vec3 vPosition;
    
    void main() {
      // Use vPosition if needed for coloring based on world position
      gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0);
    }
  `
);

// Then in your component, update the time uniform
useFrame((state) => {
  if (materials.current) {
    materials.current.uniforms.time.value = state.clock.elapsedTime;
  }
});

To animate points along specific paths, you would typically:

1. Either store path data in additional buffer attributes
2. Or calculate the path mathematically in the shader based on the point's original position and time

If you need to pass complex path data, consider using texture maps to store path information that the shader can sample based on point index or position.