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// Copyright (C) 2021-2023 Michael Fabian 'Xaymar' Dirks <info@xaymar.com>
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#define IS_FILTER
#include "../base.effect"

//-----------------------------------------------------------------------------
// Uniforms
//-----------------------------------------------------------------------------

uniform texture2d DisplacementMap<
	string name = "Displacement Map";
	string description = "A standard normal map to be used for displacement";
	string field_type = "input";
>;

uniform float DisplacementRange<
	string name = "Displacement Range";
	string field_type = "slider";
	string suffix = " px";
	float minimum = -1000.0;
	float maximum = 1000.0;
	float step = 0.01;
	float scale = 1.00;
> = 10.0;

//-----------------------------------------------------------------------------
// Technique: Version_1_0
//-----------------------------------------------------------------------------

float4 DisplacementPixelShader_v1(VertexInformation vtx) : TARGET {
	// Calculate proper offset.
	// 1. Sample the DisplacementMap texture.
	float2 offset = DisplacementMap.Sample(LinearClampSampler, vtx.texcoord0.xy).rg;
	// 2. Convert from [+0.0, +1.0] to [-0.5, +0.5].
	offset -= .5f;
	// 3. Fix the aliasing that happens with 8bpc normal maps, which also gives us the range [-1.0, +1.0].
	offset = floor(abs(offset * 255.f)) / 127.f * sign(offset);
	// 4. Scale to correct range specified by the user.
	offset *= DisplacementRange * ViewSize.zw;
	// 5. Calculate final sampled UV.
	float2 sample_uv = vtx.texcoord0.xy + offset;

	// Sample the Input texture at sample_uv.
	return InputA.Sample(LinearClampSampler, sample_uv);
}

technique Version_1_0 {	
	pass
	{
		vertex_shader = DefaultVertexShader(vtx);
		pixel_shader = DisplacementPixelShader_v1(vtx);
	}
}
