Setting glslVersion GLSL3 on a three.js ShaderMaterial removes the gl_FragColor its own chunks write to

Fact

three.js compiles every non-raw ShaderMaterial as #version 300 es already, with gl_FragColor defined to a declared pc_fragColor output. Setting glslVersion: THREE.GLSL3 upgrades nothing: it only drops those two lines and expects you to declare your own out vec4. Chunks such as #include <colorspace_fragment> still assign to gl_FragColor, so the fragment shader fails with "'gl_FragColor' : undeclared identifier" and "'linearToOutputTexel' : no matching overloaded function found".

Why it matters

GLSL3 is usually set to get sampler2DArray, texture() or integer attributes, which work without it. The broken material draws nothing while every other material renders, so it reads as missing geometry; the only trace is a shader error logged once and a stream of "useProgram: program not valid" warnings.

How to apply

• Leave glslVersion unset on ShaderMaterial; GLSL ES 3.00 features are already available, and attribute/varying map to in/out by define.
• Set THREE.GLSL3 only on a RawShaderMaterial, or when the shader declares its own output and includes no chunk that writes gl_FragColor.