Godot: Light Blocking Bug With FOV Override On Meshes

by Alex Johnson 54 views

Have you encountered strange light blocking artifacts in your Godot Engine projects when using FOV override on meshes? This article dives deep into a peculiar issue affecting Godot 4.5.1, specifically when the Forward+ renderer is in play. We'll explore the problem, how to reproduce it, and what might be causing this visual glitch.

Understanding the Light Blocking Issue with FOV Override

When working with 3D graphics in Godot, controlling the field of view (FOV) is crucial for achieving the desired visual perspective. The FOV override feature in Godot's StandardMaterial3D allows developers to adjust the FOV for individual meshes, offering creative control over how objects are rendered. However, a strange issue arises when this feature interacts with lights, particularly when a mesh isn't entirely within the light's frustum or radius. This results in light blocking artifacts that can be visually jarring.

The issue manifests as unexpected shadows or dark areas on the mesh, even though the light source should illuminate the entire surface. This problem seems specific to the Forward+ renderer and doesn't appear when using the Mobile or Compatibility renderers. If you're aiming for high-fidelity visuals and utilizing the Forward+ renderer, this bug can be a significant hurdle.

This problem particularly affects projects that require precise control over lighting and rendering, making it essential to understand and potentially work around this limitation. Game developers, especially those creating visually intensive scenes, might find themselves grappling with this artifact. So, how can you spot this issue in your project, and what steps can you take to address it?

Reproducing the Light Blocking Bug

To better understand the issue, it's important to be able to reproduce it consistently. This allows for easier testing of potential solutions or workarounds. Here’s a step-by-step guide to replicate the light blocking bug in Godot 4.5.1:

  1. Create a Mesh Instance: Begin by adding a MeshInstance node to your scene. This will serve as the object that exhibits the light blocking issue. You can use any basic mesh shape, such as a cube or a sphere.
  2. Assign a Mesh and Material: Next, assign a mesh to the MeshInstance. You can use a built-in mesh or import one from an external source. Then, create a new StandardMaterial3D and assign it to the MeshInstance.
  3. Enable FOV Override: Within the StandardMaterial3D settings, locate and enable the “FOV Override” option. This is the key step that triggers the bug when combined with specific lighting conditions.
  4. Set the FOV: Adjust the FOV value to something lower than the primary camera’s FOV. This difference in FOV is crucial for the issue to manifest. Experiment with different FOV values to see the effect on the light blocking.
  5. Create a Light 3D Node: Add any Light 3D node to your scene, such as a DirectionalLight3D or OmniLight3D. This will be the light source that interacts with the mesh.
  6. Position the Light: Position the light node so that its radius or frustum does not entirely cover the mesh. This is the final trigger for the bug. The mesh needs to be partially outside the light’s influence to exhibit the artifact.

Once you’ve followed these steps, you should observe the strange light blocking artifacts on the mesh. The areas of the mesh that are outside the light's direct influence will appear darker or shadowed in an unnatural way. This reproduction process helps confirm the issue and allows you to test any potential fixes or adjustments to your scene.

System Information and Tested Versions

The light blocking issue has been reproduced in Godot v4.5.1.stable [f62fdbde1]. It's important to note the specific version as the bug may or may not be present in other versions. Here’s a detailed breakdown of the system information used during testing:

  • Operating System: Windows 11 (build 26200)
  • Rendering: Multi-window, 1 monitor
  • Renderer: Vulkan (Forward+)
  • Graphics Card: dedicated NVIDIA GeForce RTX 3050 (NVIDIA; 32.0.15.7700)
  • Processor: AMD Ryzen 7 7800X3D 8-Core Processor (16 threads)
  • Memory: 31.11 GiB

This information helps to contextualize the issue and provides a reference point for other users who may be experiencing the same problem. The fact that the bug is reproducible on a system with a dedicated NVIDIA GeForce RTX 3050 suggests that it is not limited to low-end hardware. The use of the Vulkan (Forward+) renderer is also a key factor, as the issue has not been observed with the Mobile or Compatibility renderers.

Issue Description: Deep Dive into the Artifacts

The core issue revolves around how Light 3D nodes interact with meshes when the