Simple 2D Shader

[Chase.XNA]

I never knew this and it always drove me crazy why a simple shader wouldn't give me the same results as a SpriteBatch, well finally I found out why. You have to subtract half a pixel from the x/y of a vertex. Who would have thought...

float light = 1.0f;
sampler textureSampler;
float4x4 worldViewProj : WORLDVIEWPROJ;

struct PositionTexCoord
{
	float4 Position : POSITION0;
	float2 TexCoord : TEXCOORD0;
};

float4 PS_Process(PositionTexCoord IN) : COLOR
{
	return tex2D(textureSampler, IN.TexCoord) * light;
}

void VS_Process(in PositionTexCoord IN, out PositionTexCoord OUT)
{
	float4 position = IN.Position;
	
	position.x -= 0.5f;
	position.y -= 0.5f;

	OUT.Position = mul(position, worldViewProj);
	OUT.TexCoord = IN.TexCoord;
}

technique Baisc
{
	pass p0
	{
		vertexshader = compile vs_2_0 VS_Process();
		pixelshader = compile ps_2_0 PS_Process();
	}
}

[Jeff]

Originally Posted by Chase.XNA

I never knew this and it always drove me crazy why a simple shader wouldn't give me the same results as a SpriteBatch, well finally I found out why. You have to subtract half a pixel from the x/y of a vertex. Who would have thought...

float light = 1.0f;
sampler textureSampler;
float4x4 worldViewProj : WORLDVIEWPROJ;

struct PositionTexCoord
{
	float4 Position : POSITION0;
	float2 TexCoord : TEXCOORD0;
};

float4 PS_Process(PositionTexCoord IN) : COLOR
{
	return tex2D(textureSampler, IN.TexCoord) * light;
}

void VS_Process(in PositionTexCoord IN, out PositionTexCoord OUT)
{
	float4 position = IN.Position;
	
	position.x -= 0.5f;
	position.y -= 0.5f;

	OUT.Position = mul(position, worldViewProj);
	OUT.TexCoord = IN.TexCoord;
}

technique Baisc
{
	pass p0
	{
		vertexshader = compile vs_2_0 VS_Process();
		pixelshader = compile ps_2_0 PS_Process();
	}
}

Hah, i remember reading about that on MSDN, i believe the reason you don't do this for normal texturing is because you want each pixel to blend with the pixels beside it, this way your textures ingame look smooth.