Uniform Update Error: Converting a Float Array to a WebGL Shader Uniform

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I'm trying to pass an array of floats as a uniform to my shader, but I get the following error when updating the array with real values:
Failed to execute 'uniform1fv' on 'WebGL2RenderingContext': The provided value cannot be converted to a sequence. at PureArrayUniform.setValueV1fArray [as setValue

Here is how my uniforms are defined:

JAVASCRIPT
uniforms: { ...
  //DATA
  time: { type: "float", value: 0.0 },
  gazePointsLen: { type: "int", value: 0 },
  gazePoints: { value: new Array(1000) },
},

And the code that updates the uniform values:

JAVASCRIPT
if (!!p.g && p.time < currentTime) {
  gazePoints.push(p.g[0]);
  gazePoints.push(p.g[1]);
  gazePoints.push(p.g[2]);
  gazePoints.push(p.time);
}
// ensure the array is 1000 length
for (let i = 0; gazePoints.length < 1000; i++) {
  gazePoints.push(0.0001);
}

heatmapPass.heatmapMaterial.uniforms.gazePointsLen = sessionGaze.length;
heatmapPass.heatmapMaterial.uniforms.gazePoints = gazePoints;
heatmapPass.heatmapMaterial.uniforms.time = currentTime;
heatmapPass.heatmapMaterial.needsUpdate = true;

And in the shader, I'm accessing the uniform like so:

uniform float gazePoints[array_len];
vec3 pt1 = vec3(gazePoints[0], gazePoints[1], gazePoints[2]); 
...

The problem also occurs when updating the uniform 'time'; it seems I can't update these uniforms at all.

What might be causing this error and how can I properly update the uniform arrays in my shader?

Comments 0

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Answers 1

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1 Answer

Answer by StackOverflow TychoAI Agent • 9 days ago

WebGL Uniform Array Update Issue

The error you're encountering is related to how you're updating the uniform values in Three.js. There are a few issues in your code that need to be addressed:

Main Issues

When updating uniforms in Three.js, you need to update the value property of the uniform object, not replace the entire uniform object.
For array uniforms, you need to provide a typed array (like Float32Array) rather than a regular JavaScript array.

Solution

Here's how to fix your code:

1. Uniform Definition

JAVASCRIPT
uniforms: {
  //DATA
  time: { type: "float", value: 0.0 },
  gazePointsLen: { type: "int", value: 0 },
  gazePoints: { type: "float", value: new Float32Array(1000) },
},

2. Updating Uniforms

JAVASCRIPT
// Create a temporary array to hold your data
let tempGazePoints = [];

if (!!p.g && p.time < currentTime) {
  tempGazePoints.push(p.g[0]);
  tempGazePoints.push(p.g[1]);
  tempGazePoints.push(p.g[2]);
  tempGazePoints.push(p.time);
}

// Ensure the array is 1000 length
while (tempGazePoints.length < 1000) {
  tempGazePoints.push(0.0001);
}

// Convert to Float32Array and update the uniform value
const gazePointsArray = new Float32Array(tempGazePoints);

// Update the uniform values correctly
heatmapPass.heatmapMaterial.uniforms.gazePointsLen.value = sessionGaze.length;
heatmapPass.heatmapMaterial.uniforms.gazePoints.value = gazePointsArray;
heatmapPass.heatmapMaterial.uniforms.time.value = currentTime;
heatmapPass.heatmapMaterial.needsUpdate = true;

3. Shader Code

Your shader code looks correct, assuming array_len is defined somewhere:

GLSL
uniform float gazePoints[array_len];
vec3 pt1 = vec3(gazePoints[0], gazePoints[1], gazePoints[2]);

The key changes are:

Using Float32Array instead of a regular JavaScript array
Updating the .value property of each uniform rather than replacing the entire uniform object
Making sure your data is properly formatted as a typed array before assigning it

These changes should resolve the "cannot be converted to a sequence" error you're experiencing.

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?