[Bug]: DirectBRDFSpecular FP16 overflow clamp missing for Linux (Vulkan/OpenGL Core)

[decentraland-bot]

Bug Report

Description

The DirectBRDFSpecular function in Runtime/Shaders/Scene/URP/Lighting.hlsl has an FP16 overflow protection guard that only covers mobile and Switch platforms:

#if defined (SHADER_API_MOBILE) || defined (SHADER_API_SWITCH)
    specularTerm = specularTerm - HALF_MIN;
    specularTerm = clamp(specularTerm, 0.0, 100.0); // Prevent FP16 overflow on mobiles
#endif

This condition is incomplete — Linux using Vulkan (SHADER_API_VULKAN) or OpenGL Core (SHADER_API_GLCORE) is not covered, yet those backends also use true 16-bit half-precision types and are susceptible to the same FP16 overflow.

Steps to Reproduce

1. Run Decentraland on Linux (Vulkan or OpenGL Core)
2. Observe broken specular highlights / rendering artifacts in scenes

Expected Behavior

Specular term is clamped to [0, 100] on all platforms where half is a true 16-bit type, including Linux.

Actual Behavior

On Linux, the clamp is skipped, causing FP16 overflow and visual artifacts in the specular BRDF.

Fix

Expand the #if guard to include SHADER_API_VULKAN and SHADER_API_GLCORE, or remove the guard entirely and apply the clamp unconditionally (safe, since it's a no-op on 32-bit float platforms).

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Reported via Slack by Esteban Ordano