I have a 3D model in blender with custom normals that I baked onto the vertex colors. In godot, I'm trying to use the vertex colors as normal for my toon shader to get stylized shadowing on the face. However, the lighting seems borked with the shader I'm using. The shader code is below:


>! shader_type spatial;
>! 
>! #define USE_RIM 1
>! 
>! #define USE_PIXELART 1
>! #define USE_SMOOTH_PIXELART 1
>! 
>! #define USE_ALPHA 1
>! #define USE_DISABLE_CULL 1
>! 
>! #define USE_SUBSURFACESCATTERING 1
>! 
>! render_mode 
>! 	#if USE_DISABLE_CULL
>! 		cull_disabled;
>! 	#else
>! 		cull_back;
>! 	#endif
>! 
>! group_uniforms Toon;
>! uniform float     ToonRampOffset:     hint_range(0.0, 1.0) = 0.5;
>! uniform float     ToonRampSmoothness: hint_range(0.0, 1.0) = 0.05;
>! uniform vec3      ToonRampTinting:    source_color;
>! 
>! #if USE_RIM
>! 	group_uniforms Rim;
>! 	uniform float     RimPower:           hint_range(0.0, 10.0) = 1.0;
>! 	uniform float     RimCutOff:          hint_range(0.0, 1.0) = 0.5;
>! 	uniform float     RimSmoothness:      hint_range(0.0, 1.0) = 0.05;
>! 	uniform float     RimLightBrightness: hint_range(0.0, 50.0) = 20.0;
>! #endif
>! 
>! #if USE_SUBSURFACESCATTERING
>! 	group_uniforms SubsurfaceScattering;
>! 	uniform float     SubSurfDistortion:  hint_range(0.0, 5.0) = 1.0;
>! 	uniform vec3      SubSurfTint:        source_color;
>! 	uniform float     SubSurfBrightness:  hint_range(0.0, 10.0) = 3.0;
>! 	uniform float     SubSurfCutoff:      hint_range(0.0, 1.0) = 0.5;
>! 	uniform float     SubSurfSmoothness:  hint_range(0.0, 1.0) = 0.05;
>! 	uniform sampler2D SubSurfTexture:  source_color, hint_default_white;
>! 	
>! #endif
>! 
>! group_uniforms Texture;
>! #if (USE_SMOOTH_PIXELART || !USE_PIXELART)
>! 	uniform sampler2D Texture:            source_color, filter_linear_mipmap_anisotropic;
>! #else 
>! 	uniform sampler2D Texture:            source_color, filter_nearest_mipmap_anisotropic;
>! #endif
>! 
>! #if USE_RIM
>! 	float fresnel(float amount, vec3 normal, vec3 view) {
>! 		return pow((1.0 - clamp(dot(normalize(normal), normalize(view)), 0.0, 1.0 )), amount);
>! 	}
>! #endif
>! 
>! #if USE_SMOOTH_PIXELART
>! 	vec4 texture_point_smooth(sampler2D smp, vec2 uv, vec2 pixel_size) {
>! 		vec2 ddx = dFdx(uv);
>! 		vec2 ddy = dFdy(uv);
>! 		vec2 lxy = sqrt(ddx * ddx + ddy * ddy);
>! 		
>! 		vec2 uv_pixels = uv / pixel_size;
>! 		
>! 		vec2 uv_pixels_floor = round(uv_pixels) - vec2(0.5f);
>! 		vec2 uv_dxy_pixels = uv_pixels - uv_pixels_floor;
>! 		
>! 		uv_dxy_pixels = clamp((uv_dxy_pixels - vec2(0.5f)) * pixel_size / lxy + vec2(0.5f), 0.0f, 1.0f);
>! 		
>! 		uv = uv_pixels_floor * pixel_size;
>! 		
>! 		return textureGrad(smp, uv + uv_dxy_pixels * pixel_size, ddx, ddy);
>! 	}
>! #endif
>! void vertex () {
>! 	//set range from 0..1 to -1..1
>! 	vec3 normal = COLOR.rgb * 2.0 - 1.0;
>! 	NORMAL = normal;
>! }
>! void fragment() {
>! 	vec4 textureColor;
>! 	
>! 	#if USE_SMOOTH_PIXELART
>! 		vec2 tex_size = 1.0f / vec2(textureSize(Texture, 0));
>! 		textureColor = texture_point_smooth(Texture, UV, tex_size);
>! 	#else
>! 		textureColor = texture(Texture, UV);
>! 	#endif
>! 		ALBEDO = textureColor.rgb;
>! 
>! 	#if USE_ALPHA
>! 		ALPHA = textureColor.a;
>! 		ALPHA_SCISSOR_THRESHOLD = 0.5;
>! 	#endif
>! }
>! 
>! void light() {
>! 	// Diffuse Shading
>! 	float d =  dot(NORMAL,LIGHT) * 0.5 + 0.5;
>! 	float toonRamp = smoothstep(ToonRampOffset, ToonRampOffset + ToonRampSmoothness, d);
>! 	
>! 	// Shadows
>! 	toonRamp *= ATTENUATION;
>! 	
>! 	vec3 toonRampOutput = LIGHT_COLOR * toonRamp;
>! 	vec3 ambientLightOutput = ALBEDO * ToonRampTinting;
>! 	DIFFUSE_LIGHT += clamp((toonRampOutput - ambientLightOutput), vec3(0.0), vec3(1.0));
>! 	
>! 	
>! 	#if USE_RIM
>! 		float fresnel = fresnel(RimPower, NORMAL, VIEW);
>! 		float d2 = dot(NORMAL, LIGHT);
>! 		d2 *= fresnel;
>! 		d2 = smoothstep(RimCutOff, RimCutOff + RimSmoothness, d2);
>! 		
>! 		vec3 rimOutput =  d2 * RimLightBrightness * ALBEDO;
>! 		
>! 		DIFFUSE_LIGHT += rimOutput;
>! 	#endif
>! 	
>! 	
>! 	
>! 	#if USE_SUBSURFACESCATTERING
>! 		float subSurfBack = dot(VIEW, -(LIGHT + NORMAL * SubSurfDistortion));
>! 		float subSurfFront = dot(VIEW, LIGHT - NORMAL * SubSurfDistortion);
>! 		subSurfBack = max(subSurfBack, 0.0);
>! 		subSurfFront = max(subSurfFront, 0.0);
>! 		
>! 		float subSurfScattering = smoothstep(SubSurfCutoff, SubSurfCutoff + SubSurfSmoothness, subSurfBack + subSurfFront); 
>! 		
>! 		vec3 subSurfColor = SubSurfTint * texture(SubSurfTexture, UV).rgb;
>! 		DIFFUSE_LIGHT += subSurfScattering * SubSurfBrightness * subSurfColor;
>! 	#endif         
>!           
>! 	
>! 	SPECULAR_LIGHT = ambientLightOutput;
>! }

The base code is from this shader: https://godotshaders.com/shader/toon-shader-for-godot-4/. I only added the below lines:

void vertex () {
    vec3 normal = COLOR.rgb * 2.0 - 1.0;
    NORMAL = normal;
}

Below is a screenshot. As you can see the shading when changing direction along the x-axis rotation is wrong. Rotation along y-axis seems to be working fine though.