mame/hlsl/phosphor.fx

// license:BSD-3-Clause
// copyright-holders:Ryan Holtz, Westley M. Martinez
//-----------------------------------------------------------------------------
// Phosphor Effect
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// Sampler Definitions
//-----------------------------------------------------------------------------

texture Diffuse;

sampler DiffuseSampler = sampler_state
{
	Texture   = <Diffuse>;
	SRGBTexture = TRUE;
	MipFilter = LINEAR;
	MinFilter = LINEAR;
	MagFilter = LINEAR;
	AddressU = CLAMP;
	AddressV = CLAMP;
	AddressW = CLAMP;
};

texture LastPass;

sampler PreviousSampler = sampler_state
{
	Texture   = <LastPass>;
	SRGBTexture = TRUE;
	MipFilter = LINEAR;
	MinFilter = LINEAR;
	MagFilter = LINEAR;
	AddressU = CLAMP;
	AddressV = CLAMP;
	AddressW = CLAMP;
};

//-----------------------------------------------------------------------------
// Vertex Definitions
//-----------------------------------------------------------------------------

struct VS_OUTPUT
{
	float4 Position : POSITION;
	float4 Color : COLOR0;
	float2 TexCoord : TEXCOORD0;
	float2 PrevCoord : TEXCOORD1;
};

struct VS_INPUT
{
	float3 Position : POSITION;
	float4 Color : COLOR0;
	float2 TexCoord : TEXCOORD0;
};

struct PS_INPUT
{
	float4 Color : COLOR0;
	float2 TexCoord : TEXCOORD0;
	float2 PrevCoord : TEXCOORD1;
};

//-----------------------------------------------------------------------------
// Phosphor Vertex Shader
//-----------------------------------------------------------------------------

uniform float2 ScreenDims;
uniform float2 TargetDims;

uniform bool Passthrough;

VS_OUTPUT vs_main(VS_INPUT Input)
{
	VS_OUTPUT Output = (VS_OUTPUT)0;

	Output.Position = float4(Input.Position.xyz, 1.0f);
	Output.Position.xy /= ScreenDims;
	Output.Position.y = 1.0f - Output.Position.y; // flip y
	Output.Position.xy -= 0.5f; // center
	Output.Position.xy *= 2.0f; // zoom

	Output.TexCoord = Input.TexCoord;
	Output.TexCoord += 0.5f / TargetDims; // half texel offset correction (DX9)

	Output.PrevCoord = Output.TexCoord;

	Output.Color = Input.Color;

	return Output;
}

//-----------------------------------------------------------------------------
// Phosphor Pixel Shader
//-----------------------------------------------------------------------------

uniform int Mode = 0;
uniform float DeltaTime = 0.0f;
uniform float3 TimeConstant = { 0.0f, 0.0f, 0.0f };
uniform float3 Beta = { 0.0f, 0.0f, 0.0f };
static const float TAU_FACTOR = 0.4342944819;
static const float GAMMA_INV_FACTOR = TAU_FACTOR / 100;
// sRGB half-step for small intensities
float THRESHOLD = 0.5f / 255.0f / 12.92f;

float4 ps_main(PS_INPUT Input) : COLOR
{
	float4 CurrPix = tex2D(DiffuseSampler, Input.TexCoord);
	float3 PrevPix = tex2D(PreviousSampler, Input.PrevCoord).rgb;
	float r = PrevPix.r;
	float g = PrevPix.g;
	float b = PrevPix.b;

	if (Mode == 0) {
		r = 0;
		g = 0;
		b = 0;
	}
	else if (Mode == 1) {
		float3 tau = TimeConstant * TAU_FACTOR;

		r *= tau.r == 0 ? 0 : exp(-DeltaTime / tau.r);
		g *= tau.g == 0 ? 0 : exp(-DeltaTime / tau.g);
		b *= tau.b == 0 ? 0 : exp(-DeltaTime / tau.b);
	}
	else {
		float3 gamma = 1 / (TimeConstant * GAMMA_INV_FACTOR);

		if (r != 0.0f)
			r = pow(gamma.r * DeltaTime + pow(1 / r, 1 / Beta.r),
			        -Beta.r);
		if (g != 0.0f)
			g = pow(gamma.g * DeltaTime + pow(1 / g, 1 / Beta.g),
			        -Beta.g);
		if (b != 0.0f)
			b = pow(gamma.b * DeltaTime + pow(1 / b, 1 / Beta.b),
			        -Beta.b);
	}
	// Prevent burn-in
	if (DeltaTime > 0.0f) {
		r = max(0.0f, r - THRESHOLD);
		g = max(0.0f, g - THRESHOLD);
		b = max(0.0f, b - THRESHOLD);
	}
	r = max(CurrPix.r, r);
	g = max(CurrPix.g, g);
	b = max(CurrPix.b, b);
	return Passthrough ?  CurrPix : float4(r, g, b, CurrPix.a);
}

//-----------------------------------------------------------------------------
// Phosphor Technique
//-----------------------------------------------------------------------------

technique DefaultTechnique
{
	pass Pass0
	{
		SRGBWriteEnable = TRUE;
		Lighting = FALSE;

		VertexShader = compile vs_2_0 vs_main();
		PixelShader  = compile ps_2_0 ps_main();
	}
}