vvvv-troubleshooting

Original：🇺🇸 English

Translated

Diagnoses and fixes common vvvv gamma errors in C# nodes, SDSL shaders, and runtime behavior. Use when encountering errors, exceptions, crashes, red nodes, shader compilation failures, missing nodes in the browser, performance issues, or unexpected behavior.

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Sourcetebjan/vvvv-skills

Added on2026-02-17

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vvvv gamma Troubleshooting

C# / ProcessNode Issues

"Node" Suffix in Class Name

Symptom: Node works but has ugly name in vvvv. Fix: Remove "Node" suffix — vvvv convention forbids it.

csharp

// WRONG
[ProcessNode]
public class SteeringBehaviorNode { }

// CORRECT
[ProcessNode]
public class SteeringBehavior { }

Out Parameters After Inputs

Symptom: Pins appear in wrong order or node doesn't compile correctly. Fix:

out

parameters must come FIRST in Update signature.

csharp

// WRONG
public void Update(float input = 0f, out float result) { ... }

// CORRECT
public void Update(out float result, float input = 0f) { ... }

Node Not Appearing in Node Browser

Symptom: Your C# class exists but doesn't show up in vvvv. Fix: Check these in order:

```
[assembly: ImportAsIs]
```
attribute exists in your project
```
[ProcessNode]
```
attribute on the class
Project targets
```
net8.0
```
DLL is in the correct
```
lib/net8.0/
```
path relative to
```
.vl
```
document
Project builds without errors

Allocations Causing Frame Drops

Symptom: GC spikes, stuttering, frame drops. Diagnosis: Allocations in the Update loop.

Common culprits:

```
new
```
keyword in Update method
LINQ operators (
```
.Where()
```
,
```
.Select()
```
,
```
.ToList()
```
)
String concatenation (
```
+
```
operator on strings)
Boxing value types (passing
```
int
```
where
```
object
```
expected)

Fix: Cache everything, pre-allocate buffers, eliminate LINQ from hot paths.

Missing Change Detection

Symptom: CPU usage high even when nothing changes. Fix: Compare inputs to cached values, only recompute on change.

csharp

if (param != _lastParam)
{
    _cached = Compute(param);
    _lastParam = param;
}
result = _cached; // Always output cached

Downstream Nodes See null/default

Symptom: Connected nodes get no data, even though the node "works". Fix: Always output cached result, even when no computation happens.

csharp

// WRONG — output is only set inside the if block
public void Update(out float result, float input = 0f)
{
    if (input != _last)
    {
        result = Compute(input);
        _last = input;
    }
    // result is unassigned when input hasn't changed!
}

// CORRECT — always assign output
public void Update(out float result, float input = 0f)
{
    if (input != _last)
    {
        _cached = Compute(input);
        _last = input;
    }
    result = _cached;
}

SDSL Shader Issues

For SDSL syntax rules, common mistakes, and correct/wrong examples, see vvvv-shaders/syntax-rules.md. Key issues:

static const

scope, missing semicolons, missing

override

, enum binding format.

Runtime Issues

Memory Leaks

Symptom: Memory usage grows over time. Causes:

Missing
```
IDisposable
```
on nodes with native resources
COM objects (
```
ComPtr<T>
```
) not disposed
Event handler subscriptions not unsubscribed

Thread Safety

Symptom: Intermittent crashes, data corruption. Fix:

Update()

runs on the main thread. Capture

SynchronizationContext

in the constructor, then marshal background results back:

csharp

private SynchronizationContext _vlSyncContext;

public MyNode()
{
    _vlSyncContext = SynchronizationContext.Current!;
}

// From background thread:
_vlSyncContext.Post(_ => { /* runs on VL thread */ }, null);

Circular Dependencies

Symptom: vvvv warns about circular dependency, patch won't compile. Fix: Insert a

FrameDelay

node to break the cycle.

Build Issues

Target Framework Mismatch

Symptom: DLL loads but types aren't found. Fix: Ensure

.csproj

targets

net8.0

(matching vvvv gamma's runtime).

Assembly Version Conflicts

Symptom:

FileLoadException

or

TypeLoadException

at runtime. Fix: Align package versions with vvvv's bundled versions. Check vvvv's

lib/

folder for reference.

For detailed error-to-solution mapping, see error-catalog.md.

vvvv-troubleshooting

NPX Install

Tags

SKILL.md Content

vvvv gamma Troubleshooting

C# / ProcessNode Issues

"Node" Suffix in Class Name

Out Parameters After Inputs

Node Not Appearing in Node Browser

Allocations Causing Frame Drops

Missing Change Detection

Downstream Nodes See null/default

SDSL Shader Issues

Runtime Issues

Memory Leaks

Thread Safety

Circular Dependencies

Build Issues

Target Framework Mismatch

Assembly Version Conflicts