BabylonJS/Babylon.js · error · Error

Failed to read frame time. Invalid value

Error message

Failed to read frame time. Invalid value 

What it means

ReadBvh requires the frame time to be a positive number since it computes frameRate = 1 / frameTime. This error is thrown when parseFloat succeeds but the value is zero or negative, which would produce a non-finite or negative frame rate.

Source

Thrown at packages/dev/loaders/src/BVH/bvhLoader.ts:386

        throw new Error("Failed to read number of frames.");
    }
    context.numFrames = numFrames;

    // frame time
    const frameTimeLine = lines.shift();
    if (!frameTimeLine) {
        throw new Error("Unexpected end of file before frame time");
    }
    const frameTimeTokens = frameTimeLine.trim().split(/[\s]+/);
    if (frameTimeTokens.length < 3) {
        throw new Error("Invalid frame time line");
    }
    const frameTime = parseFloat(frameTimeTokens[2]);
    if (isNaN(frameTime)) {
        throw new Error("Failed to read frame time.");
    }
    if (frameTime <= 0) {
        throw new Error("Failed to read frame time. Invalid value " + frameTime);
    }

    context.frameRate = 1 / frameTime;

    // read frame data line by line
    for (let i = 0; i < numFrames; ++i) {
        const frameLine = lines.shift();
        if (!frameLine) {
            continue;
        }
        const tokens = frameLine.trim().split(/[\s]+/) || [];
        ReadFrameData(tokens, i, root, { i: 0 });
    }

    context.root = root;

    ConvertNode(context.root, null, context);

View on GitHub (pinned to 0592b347b8)

Solutions

1. Set the frame time to a positive value in seconds, e.g. 'Frame Time: 0.033333' (30 fps)
2. Compute the correct value as 1 / desiredFps from the source animation's frame rate
3. Re-export the BVH from the original animation tool so the header is regenerated correctly
4. Validate that the parsed frame time is > 0 before calling ReadBvh when processing untrusted files

Example fix

// before
Frame Time: 0
// after
Frame Time: 0.033333

function validateFrameTimePositive(text) {
  const m = text.match(/^Frame Time:\s*([^\s]+)\s*$/im);
  const ft = m ? parseFloat(m[1]) : NaN;
  if (!(ft > 0)) throw new Error('Frame Time must be > 0, got ' + ft);
}

function isPositiveFrameTime(text: string): boolean {
  const m = text.match(/^Frame Time:\s*([^\s]+)\s*$/im);
  const ft = m ? parseFloat(m[1]) : NaN;
  return Number.isFinite(ft) && ft > 0;
}

try {
  skeleton.readBvh(text);
} catch (e) {
  if (e instanceof Error && e.message.startsWith('Failed to read frame time. Invalid value')) {
    console.error('Frame Time must be a positive number of seconds');
  } else throw e;
}

When it happens

Trigger: A frame-time line such as 'Frame Time: 0' or 'Frame Time: -0.033' in the BVH file; also a template file where the value placeholder was replaced with 0.

Common situations: Auto-generated BVH with an uninitialized frame-time variable, hand-edited files where the value was zeroed out, or corrupted exports where the header value was overwritten with a default/sentinel.

Understand the failure class

Background: "must be positive", "Invalid value": how libraries reject invalid parameter values (ValueError, ArgumentError, INVALID_PARAMETER_VALUE) — this error's family across 28 libraries.

Related errors

• Unexpected end of file before frame time
• Invalid frame time line
• Failed to read frame time.
• Nothing else parsed so far
• Invalid JSON Format. Check the frame values and make sure t

AI-assisted analysis of BabylonJS/Babylon.js@0592b347b8 (2026-08-30). Data as JSON: /api/errors/abd5f0e543d76c67. Report an issue: GitHub.