Jump to content

  • Log In with Google      Sign In   
  • Create Account

We're offering banner ads on our site from just $5!

1. Details HERE. 2. GDNet+ Subscriptions HERE. 3. Ad upload HERE.


Lotes

Member Since 08 Nov 2012
Offline Last Active Yesterday, 09:34 AM

Topics I've Started

Problems with Alchemy SSAO implementation

03 November 2014 - 10:29 AM

I want to implement the Alchemy SSAO algorithm (see http://graphics.cs.williams.edu/papers/AlchemyHPG11/).

Some code is taken from here:
http://www.gamedev.net/topic/648090-alchemy-ambient-occlusion/

But my shader is inverted on some shapes (see screenshot). I don't know where to search for the bug.
Can someone help me?

Here is my shader code...

The input is a texture with normals in world space (rgb) and depth (a) and texture with noise. The noise texture is currently not read.

Two user constants are defined for the texture width and texture height.

#define PI    3.14159265

cbuffer ConstBuffer : register(c0)
{
    float width; //texture width
    float height; //texture height    
}

static const int samplesCount = 16;
static const int spiralTurns = 1;

static const float radius = 0.25;
static const float epsilon = 0.01;

static const float zNear = 0.1;
static const float zFar = 500;
static const float fov = 45.0 / 180.0 * PI;
static const float2 focalLength = float2(1.0/tan(fov*0.5) * height / width, 1.0/tan(fov*0.5));

Texture2D normalDepthTexture: register(t0);
Texture2D randomTexture: register(t1);

SamplerState textureSampler
{
    Filter = MIN_MAG_MIP_LINEAR;
    AddressU = Wrap;
    AddressV = Wrap;
};

struct VS_INPUT
{
    float3 position             : POSITION;    
    float3 normal               : NORMAL;
    float2 uv                   : TEXCOORD;
};

struct VS_OUTPUT
{
    float4 position             : SV_POSITION;
    float2 uv                   : TEXCOORD;
};

VS_OUTPUT VShader(VS_INPUT i)
{
    VS_OUTPUT vo;    
    vo.position = float4(i.position, 1);    
    vo.uv = i.uv;
    return vo;
}

float4 readNormalDepth(float2 uv)
{
    return normalDepthTexture.SampleLevel(textureSampler, uv, 0.0f);
}

float3 readNormal(float2 uv)
{
    return normalize((readNormalDepth(uv).xyz - 0.5) * 2);
}

float readDepth(float2 uv)
{
    return readNormalDepth(uv).a;
}

float linearDepth(float d)
{
	d = d*2.0 - 1.0;
	float2 lin = float2((zNear-zFar)/(2.0*zNear*zFar), (zNear+zFar)/(2.0*zNear*zFar));
	return -1.0/(lin.x*d+lin.y);
}

float3 getViewPosition(float2 uv)
{
	float z = linearDepth(readDepth(uv));
	float2 UVtoViewB = float2(1.0 / focalLength.x, 1.0 / focalLength.y);
	float2 UVtoViewA = 2 * UVtoViewB;	
	return float3((UVtoViewA * uv - UVtoViewB) * z, z);
}

float2 tapLocation(int sampleNumber, float spinAngle)
{
	float alpha = float(sampleNumber + 0.5) * (1.0 / samplesCount);
	float angle = alpha * (spiralTurns * 2 * PI) + spinAngle;
	float radius = alpha;
	return radius * float2(cos(angle), sin(angle));
}

float4 PShader(VS_OUTPUT i) : SV_Target
{   	
	float ao = 0;
	float3 currentPoint = getViewPosition(i.uv);
	float3 normal = readNormal(i.uv);
	float2 pixelPosition = float2(i.uv.x * width, i.uv.y * height);
	float random =
	    (3*int(pixelPosition.x)^int(pixelPosition.y)+int(pixelPosition.x)*int(pixelPosition.y))*10.0;
		//randomTexture.SampleLevel(textureSampler, i.uv, 0.0f).x;
	float diskRadius = 0.5 * focalLength.y * radius / currentPoint.z;
	[unroll]
	for(int sampleIndex=0; sampleIndex < samplesCount; sampleIndex++)
	{
		float2 offset = tapLocation(sampleIndex, random);
		float2 samplePosition = i.uv + diskRadius * offset;
		float3 samplePoint = getViewPosition(samplePosition);
		float3 v = samplePoint - currentPoint;
		float vv = dot(v, v);
		float vn = dot(v, normal);
		ao += max(0, vn + currentPoint.z * 0.001) / (vv + epsilon);		
	}
	ao *= 2.0 * PI * radius * 0.05 / samplesCount;
	ao *= 5; //makes ssao darker
	ao = min(1, max(0, 1 - ao));
    return float4(ao, ao, ao, 1);
}

Render depth to texture

08 November 2012 - 07:30 AM

Hi, I work with XNA and I want to render the depth information of my scene into a texture. But all I get is my scene (some cubes) completly colored in white. So the depth information I determined is greater or equal 1.0 I guess. How is it done right? I googled a lot, but I can't find my mistake :'-(... Do I have to make any settings in XNA before rendering?

Here are the HLSL shaders I use:

float4x4 xView;
float4x4 xProjection;
float4x4 xWorld;

struct VertexToPixel
{
	float4 Position	: POSITION;  
	float4 Color  : COLOR0;
};

struct PixelToFrame
{
	float4 Color : COLOR0;
};

VertexToPixel PositionsVS( float4 inPos : POSITION)
{
	float4x4 preViewProjection = mul (xView, xProjection);
	float4x4 preWorldViewProjection = mul (xWorld, preViewProjection);
	VertexToPixel Output = (VertexToPixel)0;
	Output.Position = mul(inPos, preWorldViewProjection);
	Output.Color.a = 1;
	Output.Color.rgb = Output.Position.z/Output.Position.w;
	return Output;
}

PixelToFrame PositionsPS(VertexToPixel PSIn)
{
	PixelToFrame Output = (PixelToFrame)0;
	Output.Color = PSIn.Color;
	return Output;
}

technique Positions
{
	pass Pass0
	{  
	  VertexShader = compile vs_3_0 PositionsVS();
	  PixelShader  = compile ps_3_0 PositionsPS();
	}
}

PARTNERS