The Visual Logger

The Visual Logger, VisLog for short, is a powerful profiling tool that allows you to easily capture, visualize, and debug in-game events. It’s commonly used with AI debug visualization, however, it’s great for a plethora of other use-cases, such as —

• Projected Actor Paths
• Collision Traces
• Attack/projectile trajectories
• networking debugging (clients Vs. Server Data Comparisons)
• Use With The Environment Query System (EQS)
• Etc.

How can I open the Visual Logger?

There are two methods that you can use to open the Visual Logger —

Method 1 — Menu Bar

The Visual Logger can be opened from the Editor Menu Bar.

Method 2 — Console Command

Use the VisLog console command to open the Visual Logger window.

Is the VisLog recording by default?

No. The VisLog only records data when it is enabled.

Use the Enable VisLog Recording function to toggle VisLogging on and off.

FVisualLogger& VisualLogger = FVisualLogger::Get();
VisualLogger.SetIsRecording(true);

How do I capture VisLog events?

There are a variety of functions and methods that can be used VisLog events. Here are a few common ones —

VisLog Location

The VisLog Location function records a particular location, represented as a sphere with a specified radius.

This function can be great for visualizing —

• hit traces
• object/data locations
• paths along segments
• etc.

VisLog Segment

The VisLog Segment function records a line with a specified start and end position.

This function can be great for visualizing —

• distance between objects
• trajectories and paths

VisLog Text

The VisLog Text function is useful for logging a simple text string, perfect for capturing data related to a specific event.

VisLog Shapes

A vast array of shapes is available for visualization when using C++, enabling you to represent almost anything. Although most of these shapes aren't directly accessible in Blueprints, they can be exposed for use within Blueprints, providing even more flexibility.

UE_VLOG_BOX

UE_VLOG_CONE

UE_VLOG_ARROW

UE_VLOG_CIRCLE

UE_VLOG_CYLINDER

And more…

While I covered the common ones, I want to at-least mention the interesting ones.

There are multiple other C++ macros that might prove useful —

UE_VLOG_MESH

The UE_VLOG_MESH macro is used to draw a custom mesh using vertices and indices. Useful for debugging issues related to collision or navigation.

The procedural mesh and geometry scripting functions are quite useful when using this macro.

UE_VLOG_HISTOGRAM

The UE_VLOG_HISTOGRAM macro is used to draw a histogram onto of the viewport, which represents a statistical distribution of a set of data. It can be used to visualize data distributes (e.g., AI decision-making weight distributions, character attribute changes, etc.)

Note: To visualize the Histogram, make sure to enable the Graphs option int he Visual Logger.

UE_VLOG_CONVEXPOLY

The UE_VLOG_CONVEXPOLY macro is used to draw a 2D convex-hull polygon. It can be used to visualize areas or regions (e.g., navigation, pathing, sight, etc.)

UE_VLOG_EVENT_WITH_DATA

The UE_VLOG_EVENT_WITH_DATA macro is used to provide custom event-based data to the Visual Logger. It can be used to record specific events or actions with associated data, providing more context for debugging and analysis.

UE_VLOG_EQS

The UE_VLOG_EQS macro is used to log data related to the Environmental Query System (EQS), which itself is a system for querying the environment to make AI-based decisions.

This macro, in particular, logs the results of EQS queries, providing insights into AI decision-making.

How can I get started with the Visual Logger in C++?

Thankfully, it’s pretty straightforward to get started with the Visual Logger in C++. Here are some code snippets to get you started —

Include

This is the required C++ include for the Visual Logger.

#include "VisualLogger/VisualLogger.h"

Define Static Log

When dealing with VisLogging, you might want to define a specific log type.

DEFINE_LOG_CATEGORY_STATIC( LogUDVisLog, Log, All )

Class

The class used to call VisLog functions.

FVisualLogger

Example

Here’s a minimal viable example for drawing a VisLog box.

#include "VisualLogger/VisualLogger.h"
 
DEFINE_LOG_CATEGORY_STATIC( LogUDVisLog, Log, All )
 
AUDVisLogExample::Example()
{
 
#if ENABLE_VISUAL_LOG
 
	if (!FVisualLogger::IsRecording()) { return; }
 
	const UWorld* World = GetWorld();
	if (!World) { return; }
 
	const FVector BoxLocation = GetActorLocation() + FVector(500.0f, 0.0f, 0.0f);
	const FVector BoxExtent(100.0f, 100.0f, 100.0f);
	const FBox Box(BoxLocation - BoxExtent, BoxLocation + BoxExtent);
	UE_VLOG_BOX(World, LogUDVisLog, Log, Box, FColor::Blue, TEXT("Draw Box"));
 
#endif
}