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-rw-r--r--hlsl/prescale.fx42
1 files changed, 30 insertions, 12 deletions
diff --git a/hlsl/prescale.fx b/hlsl/prescale.fx
index 846c02577ce..419254acd07 100644
--- a/hlsl/prescale.fx
+++ b/hlsl/prescale.fx
@@ -1,7 +1,11 @@
// license:BSD-3-Clause
-// copyright-holders:Ryan Holtz
+// copyright-holders:Ryan Holtz,Themaister,ImJezze
//-----------------------------------------------------------------------------
-// Prescale Effect
+// Pre-scale Effect
+//
+// Uses the hardware bilinear interpolator to avoid having to sample 4 times manually.
+//
+// https://github.com/libretro/common-shaders/blob/master/retro/shaders/sharp-bilinear.cg
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
@@ -13,9 +17,9 @@ texture Diffuse;
sampler DiffuseSampler = sampler_state
{
Texture = <Diffuse>;
- MipFilter = NONE;
- MinFilter = NONE;
- MagFilter = NONE;
+ MipFilter = LINEAR;
+ MinFilter = LINEAR;
+ MagFilter = LINEAR;
AddressU = CLAMP;
AddressV = CLAMP;
AddressW = CLAMP;
@@ -45,39 +49,53 @@ struct PS_INPUT
};
//-----------------------------------------------------------------------------
-// Prescale Vertex Shader
+// Pre-scale Vertex Shader
//-----------------------------------------------------------------------------
uniform float2 ScreenDims;
uniform float2 TargetDims;
+uniform float2 SourceDims;
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.TexCoord += 0.5f / targetDims; // half texel offset correction (DX9)
return Output;
}
//-----------------------------------------------------------------------------
-// Prescale Pixel Shader
+// Pre-scale Pixel Shader
//-----------------------------------------------------------------------------
float4 ps_main(PS_INPUT Input) : COLOR
{
- return tex2D(DiffuseSampler, Input.TexCoord);
+ float2 Scale = TargetDims / SourceDims;
+
+ float2 TexelDims = Input.TexCoord * SourceDims;
+ float2 i = floor(TexelDims);
+ float2 s = frac(TexelDims);
+
+ // Figure out where in the texel to sample to get the correct pre-scaled bilinear.
+ float2 CenterDistance = s - 0.5f;
+ float2 RegionRange = 0.5f - 0.5f / Scale;
+ float2 f = (CenterDistance - clamp(CenterDistance, -RegionRange, RegionRange)) * Scale + 0.5f;
+
+ float2 TexCoord = (i + f) / SourceDims;
+
+ return tex2D(DiffuseSampler, TexCoord);
}
//-----------------------------------------------------------------------------
-// Prescale Technique
+// Pre-scale Technique
//-----------------------------------------------------------------------------
technique DefaultTechnique