I'm having a hell of a time getting an L16 texture (16bit heightfield data) read in my shader and was hoping someone could spot where I'm going wrong.

I'm pretty sure the logic is just some syntax issue in my shader, but just to verify I ran everything through RenderDoc and I can see the load call being executed, however it always returns 0. I've tried a few values to no avail, checking the pipeline I can see the resource is bound and I can see the values in the resource look correct - the shader just isn't reading it for some reason.

Any thoughts?

Shader:

float4x4 WorldViewProjection	: WorldViewProjection;

// Textures
Texture2D<float4> DiffuseTexture;
Texture2D<uint> HeightmapTexture;

float MaxHeight;

// Structures
struct VSInput
{
	float4 Position		: POSITION;
	float2 Uv		: TEXCOORD0;
};

struct VSOutput
{
	float4 Position		: SV_POSITION;
	float2 Uv		: TEXCOORD0;
};

sampler LinearClampSampler
{
	Filter = Min_Mag_Mip_Linear;
	AddressU = Clamp;
	AddressV = Clamp;
};

sampler PointClampSampler
{
	Filter = Min_Mag_Mip_Point;
	AddressU = Clamp;
	AddressV = Clamp;
};

// Helper Methods
float GetHeightmapValue(float2 uv)
{
	uint rawValue = HeightmapTexture.Load(uint3(uv.x, uv.y, 0)); // <- Always returns 0,0,0,0
	return ((float)rawValue/(256.0f * 256.0f)) * MaxHeight;
}

// Vertex shaders
VSOutput ForwardRenderVS(VSInput IN)
{
	VSOutput Out = (VSOutput)0;
	float3 position = IN.Position.xyz;
	position.y = GetHeightmapValue(IN.Uv);
	Out.Position = mul(float4(position, 1.0f), WorldViewProjection);
	Out.Uv = IN.Uv;
	return Out;
}


// Fragment shaders.
float4 ForwardRenderFP(VSOutput In) : FRAG_OUTPUT_COLOR0
{
	return float4(0.0f, 1.0f, 0.0f, 0.0f);
}

// Render states.
BlendState NoBlend
{
	BlendEnable[0] = FALSE;
	RenderTargetWriteMask[0] = 15;
};

BlendState LinearBlend
{
	BlendEnable[0] = TRUE;
	SrcBlend[0] = SRC_ALPHA;
	DestBlend[0] = INV_SRC_ALPHA;
	BlendOp[0] = ADD;
	SrcBlendAlpha[0] = ZERO;
	DestBlendAlpha[0] = ZERO;
	BlendOpAlpha[0] = ADD;
	BlendEnable[1] = FALSE;
	RenderTargetWriteMask[0] = 15;
};

DepthStencilState DefaultDepthState
{
	DepthEnable = TRUE;
	DepthWriteMask = All;
	DepthFunc = Less;
	StencilEnable = FALSE;
};

RasterizerState DefaultRasterState
{
	CullMode = None;
};

RasterizerState CullBackRasterState
{
	CullMode = Front;
};

// Techniques.
technique11 ForwardRender
{
	pass pass0
	{
		SetVertexShader( CompileShader( vs_4_0, ForwardRenderVS() ) );
		SetPixelShader( CompileShader( ps_4_0, ForwardRenderFP() ) );
	
		SetBlendState( NoBlend, float4( 0.0f, 0.0f, 0.0f, 0.0f ), 0xFFFFFFFF );
		SetDepthStencilState( DefaultDepthState, 0 );
		SetRasterizerState( DefaultRasterState );
	}
}

RenderDoc image.

Are your UVs in the range [0, 1] or are they in the range [0, HeightmapDimension]? I'm pretty sure Load takes texel coordinates as integers between 0 and the width/height of the resource in texels. When you take your UVs and cast them to an int you might be getting uint3(0,0,0) every time, and simply be loading the same texture location over and over again.

Are your UVs in the range [0, 1] or are they in the range [0, HeightmapDimension]? I'm pretty sure Load takes texel coordinates as integers between 0 and the width/height of the resource in texels. When you take your UVs and cast them to an int you might be getting uint3(0,0,0) every time, and simply be loading the same texture location over and over again.

Yea I had that thought as well, even when I multiplied the uv coords (which are in 0 - 1 space) value by the dimensions of the texture, I still get all 0's back.

EDIT:

Here's the ASM, notice the r0 index value:

And here's what that value should be returning:

Thanks MJP, I'll give that a shot. Is using the Load method the best way to read that value? Or (since its going to be a float value returned anyway) go back to using SampleLevel?