BabylonJS/Babylon.js · error · Error

Unexpected end of file before frame count

Error message

Unexpected end of file before frame count

What it means

Immediately after the MOTION keyword, a valid BVH file must contain a 'Frames: <count>' line. ReadBvh shifts the next line after MOTION and throws this error when that line is undefined — the text ended right after MOTION with no frame-count line at all. The parser needs the frame count to know how many motion data lines to read, so it cannot continue.

Source

Thrown at packages/dev/loaders/src/BVH/bvhLoader.ts:358

    if (!firstLine || firstLine.trim().toUpperCase() !== _HierarchyNode) {
        throw new Error("HIERARCHY expected");
    }

    const nodeLine = lines.shift();
    if (!nodeLine) {
        throw new Error("Unexpected end of file after HIERARCHY");
    }
    const root = ReadNode(lines, nodeLine.trim(), null, context);

    // read motion data
    const motionLine = lines.shift();
    if (!motionLine || motionLine.trim().toUpperCase() !== _MotionNode) {
        throw new Error("MOTION expected");
    }

    const framesLine = lines.shift();
    if (!framesLine) {
        throw new Error("Unexpected end of file before frame count");
    }
    const framesTokens = framesLine.trim().split(/[\s]+/);
    if (framesTokens.length < 2) {
        throw new Error("Invalid frame count line");
    }

    // number of frames
    const numFrames = parseInt(framesTokens[1]);
    if (isNaN(numFrames)) {
        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");
    }

View on GitHub (pinned to 0592b347b8)

Solutions

  1. Verify the file is complete: after MOTION there must be a 'Frames: <n>' line followed by 'Frame Time:' and n data lines; re-download or re-export.
  2. Check file size against the source; a truncated transfer is the most common cause — retry the download.
  3. If generating BVH in code, append the 'Frames: N' and 'Frame Time: t' headers after MOTION.
  4. Log the last lines of the text passed to ReadBvh (text.split('\n').slice(-5)) to confirm truncation before calling.
  5. Validate with /MOTION\s*\n\s*Frames:\s*\d+/ before calling ReadBvh.

Example fix

// before
MOTION
// EOF here -> error

// after
MOTION
Frames: 60
Frame Time: 0.033333
<60 lines of frame data>
Defensive patterns

Strategy: validation

Validate before calling

function hasFramesHeader(text: string): boolean {
    return /MOTION\s*\n\s*Frames:\s*\d+/i.test(text);
}
if (!hasFramesHeader(bvhText)) {
    throw new Error("BVH file truncated before 'Frames:' line");
}
const skeleton = ReadBvh(bvhText, scene, null, options);

Try / catch

try {
    const skeleton = ReadBvh(bvhText, scene, null, options);
} catch (e) {
    if (e instanceof Error && e.message.includes("before frame count")) {
        console.error("BVH ends right after MOTION — file truncated", e);
    } else {
        throw e;
    }
}

Prevention

When it happens

Trigger: Calling ReadBvh with text that ends exactly at the 'MOTION' line (nothing after it), a file truncated between 'MOTION' and 'Frames:', or passing a string that was sliced/trimmed so trailing lines were dropped before the call.

Common situations: Truncated downloads or uploads (file cut off mid-write), server responses cut at a content-length boundary, text editors or scripts that stripped trailing lines, or generating BVH programmatically and forgetting to append the 'Frames:' header and frame data.

Related errors

AI-assisted analysis of BabylonJS/Babylon.js@0592b347b8 (2026-08-30). Data as JSON: /api/errors/c9a044e18d9401d2. Report an issue: GitHub.