Concatenating Two or More Images Together

color = texcoord.x < 0.5 ? tex2D(BackBuffer, float2((texcoord.x*2), texcoord.y)) : depth;

technique MyEffect
{
  pass first_execute
  {
    VertexShader = PostProcessVS;
    PixelShader = PS_First;
    RenderTarget = TemporaryTex_For_First;
  }
  pass second_execute
  {
    VertexShader = PostProcessVS;
    PixelShader = PS_Second;
    RenderTarget = TemporaryTex_For_Second;
  }
  pass third_execute
  {
    VertexShader = PostProcessVS;
    PixelShader = PS_Third;
    // Render to screen with using TemporaryTex_For_First and TemporaryTex_For_Second.
  }
}

// Bring to equal with game screen resolution. (BUFFER_ macro created by ReShade)

// for PS_First and PS_Third
texture TemporaryTex_For_First { Width = BUFFER_WIDTH; Height = BUFFER_HEIGHT; };
sampler TexSampler_For_First { Texture = TemporaryTex_For_First; };

// for PS_Second and PS_Third
texture TemporaryTex_For_Second { Width = BUFFER_WIDTH; Height = BUFFER_HEIGHT; };
sampler TexSampler_For_Second { Texture = TemporaryTex_For_Second; };

void PS_First(float4 pos : SV_Position, float2 texCoord : TEXCOORD, out float4 passColor : SV_Target)
{
	// Render to TemporaryTex_For_First
	passColor = float4(texCoord.x, 0.0, 0.0, 1.0); // Gradation of red
}

void PS_Second(float4 pos : SV_Position, float2 texCoord : TEXCOORD, out float4 passColor : SV_Target)
{
	// Render to TemporaryTex_For_Second
	passColor = float4(0.0, texCoord.x, 0.0, 1.0); // Gradation of green
}

void PS_Third(float4 pos : SV_Position, float2 texCoord : TEXCOORD, out float4 passColor : SV_Target)
{
	// Render to screen
	if (texCoord.x < 0.5) // Render the gradation of red to left
	{
		// texCoord 0.0 ... 0.5 for texture 0.0 ... 1.0
		passColor = tex2D(TexSampler_For_First, float2(texCoord.x * 2.0, texCoord.y));
	}
	else // Render the gradation of green to right
	{
		// texCoord 0.5 ... 1.0 for texture 0.0 ... 1.0
		passColor = tex2D(TexSampler_For_Second, float2((texCoord.x - 0.5) * 2.0, texCoord.y));
	}
}