Call SRGBToLinear in Bloom FragPrefilter Pass

[gam0022]

I fixed the Bloom Effect implementation: Calling SRGBToLinear() in the FragPrefilter Pass is missing.

This change makes Bloom Effect maintain the same appearance regardless of the Unity's Color Space setting (Gamma or Linear).

Details

The Bloom threshold is in Linear Space.

PostProcessing/PostProcessing/Runtime/Effects/Bloom.cs

Line 124 in d4eb229

float lthresh = Mathf.GammaToLinearSpace(settings.threshold.value);

On the other hand, Bloom FragPrefilter does not convert to Linear Space.

PostProcessing/PostProcessing/Shaders/Builtins/Bloom.shader

Lines 31 to 41 in d4eb229

	half4 FragPrefilter13(VaryingsDefault i) : SV_Target
	{
	half4 color = DownsampleBox13Tap(TEXTURE2D_PARAM(_MainTex, sampler_MainTex), i.texcoord, _MainTex_TexelSize.xy);
	return Prefilter(SafeHDR(color), i.texcoord);
	}
	half4 FragPrefilter4(VaryingsDefault i) : SV_Target
	{
	half4 color = DownsampleBox4Tap(TEXTURE2D_PARAM(_MainTex, sampler_MainTex), i.texcoord, _MainTex_TexelSize.xy);
	return Prefilter(SafeHDR(color), i.texcoord);
	}

The UberShader Pass calls LinearToSRGB().

PostProcessing/PostProcessing/Shaders/Builtins/Uber.shader

Lines 233 to 237 in 4bfd2ef

	#if UNITY_COLORSPACE_GAMMA
	{
	output = LinearToSRGB(output);
	}
	#endif

It means that the Linear Space Threshold is compared with the SRGB Space RenderTexutre when UNITY_COLORSPACE_GAMMA is defined (Unity Color Space: Gamma).

I fixed this implementation so that the Bloom Effect works properly even if UNITY_COLORSPACE_GAMMA is defined or not.

Results

Before (v2 branch)

The intensity of Bloom is changed by Unity's color space setting (Gamma or Linear).

After (this branch)

It maintains the same appearance regardless of the Unity's color space setting.

The original image belongs to the following site.
http://www.humus.name/index.php?page=Textures&ID=18

[gam0022]

@Chman Would you please review?