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Lotes

Member Since 08 Nov 2012
Offline Last Active Feb 19 2015 07:07 AM

Posts I've Made

In Topic: Problems with Alchemy SSAO implementation

10 November 2014 - 09:41 AM

I finally fixed it :-). The view space position was not computed correctly. And the disk radius was wrong. Screenshot appended...

//from: http://graphics.cs.williams.edu/papers/AlchemyHPG11/

#define PI 3.14159265

//Important: http://msdn.microsoft.com/en-us/library/bb509632%28v=vs.85%29.aspx
cbuffer ConstBuffer : register(c0)
{
	float4x4 inverseProjection;
	float cameraFOV;	
    float cameraZNear;
	float cameraZFar;	
	float width; 
    float height;    
}

static const float halfFOV = cameraFOV / 2;

static const int samplesCount = 16;
static const int spiralTurns = 10;

static const float radius = 0.10;
static const float beta = 0.2;
static const float epsilon = 0.01;

Texture2D normalDepthTexture: register(t0);

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 (readNormalDepth(uv).xyz - 0.5) * 2;
}

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

float linearDepth(float d)
{
	//http://www.humus.name/temp/Linearize%20depth.txt
	//returns a value between 0 (near) and 1 (far)
	return d / (cameraZFar - d * (cameraZFar - cameraZNear));
}

float3 getViewPosition(float2 uv)
{
	float depth = readDepth(uv);
	float4 screenCoordinate = 2 * (float4(uv.x, 1-uv.y, depth, 1) - 0.5);
	float4 viewCoordinate = mul(inverseProjection, screenCoordinate);
	return viewCoordinate.xyz / viewCoordinate.w;
}

float3 getPosition(float2 uv)
{
	return getViewPosition(uv);
}

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 = getPosition(i.uv);
	float currentDepth = linearDepth(readDepth(i.uv));
	float3 normal = readNormal(i.uv);
	float2 pixelPosition = i.uv * float2(width, height);
	float random = (3*int(pixelPosition.x)^int(pixelPosition.y)+int(pixelPosition.x)*int(pixelPosition.y))*10.0;
	float diskRadius = radius / (2 * (currentDepth * (cameraZFar - cameraZNear) + cameraZNear) * tan(halfFOV));
	[unroll]
	for(int sampleIndex=0; sampleIndex < samplesCount; sampleIndex++)
	{
		float2 offset = tapLocation(sampleIndex, random);
		float2 samplePosition = i.uv + diskRadius * offset;
		float3 samplePoint = getPosition(samplePosition);
		float3 v = samplePoint - currentPoint;
		float vv = dot(v, v);
		float vn = dot(v, normal);
		if(currentDepth < 1) //do not AO for far plane
			ao += max(0, vn + currentDepth * 0.001) / (vv + epsilon);
	}
	ao *= 2.0 * PI * radius * beta / samplesCount;
	ao = min(1, max(0, 1 - ao));
	return float4(ao, ao, ao, 1);	
}

In Topic: Problems with Alchemy SSAO implementation

05 November 2014 - 10:13 AM

I now think the problem is, that on the even surfaces the dot product of v and the normal (for one sample) is not zero. The "getViewPosition" function must be wrong... This function should reconstruct the world space coordinate from texture coordinate (uv) and the depth buffer.

My current version of "getWorldPosition" is something like that (it is not correct so far):
 

float3 getWorldPosition(float2 uv)
{
    float depth = readDepth(uv);
    float4 projectionPosition = float4(uv, depth, 1);
    float4 worldPosition = mul(inverseProjection, projectionPosition);    
    worldPosition /= worldPosition.w;    
    worldPosition = mul(inverseView, worldPosition);        
    return worldPosition.xyz;
}

What is the right way of reconstructing the world space coordinate?


In Topic: Render depth to texture

08 November 2012 - 09:30 AM

It works with this code. But I find it very ugly to use a magic number like 25 as a factor in this case. How can I calculate this factor from my matrices? :-/
VertexToPixel PositionsVS( float4 inPos : POSITION, float3 inNormal: NORMAL, float4 inColor: COLOR)
{
    VertexToPixel Output = (VertexToPixel)0;
    float4x4 preViewProjection = mul (xView, xProjection);
    float4x4 preWorldViewProjection = mul (xWorld, preViewProjection);
    Output.Position = mul(inPos, preWorldViewProjection);
    Output.Color = 1;
    Output.Color.rgb = Output.Position.z;
    return Output;
}
PixelToFrame PositionsPS(VertexToPixel PSIn)
{
    PixelToFrame Output = (PixelToFrame)0;
    Output.Color = PSIn.Color/25;
    return Output;
}

My cubes have a dimension of 0.9x0.9x0.9 at positions (0,0,-10), (0,0,-9) ... (0,0,10).
My camera is at (0,10,-20) looking at (0,0,0).

In Topic: Render depth to texture

08 November 2012 - 09:14 AM

they are drawn (black cubes on blue background).
changing 200 to 200.0 did not help. i think in hlsl it does not matter.

In Topic: Render depth to texture

08 November 2012 - 08:43 AM

Here is it...
VertexToPixel PositionsVS( float4 inPos : POSITION)
{
    VertexToPixel Output = (VertexToPixel)0;

    float4x4 preWorldView= mul (xWorld, xView);
    Output.Position = mul(inPos, preWorldView);
    Output.Color = 1;
    Output.Color.rgb = Output.Position.z/200;
    Output.Position = mul(Output.Position,xProjection);
    return Output;
}
PixelToFrame PositionsPS(VertexToPixel PSIn)
{
    PixelToFrame Output = (PixelToFrame)0;
    Output.Color = PSIn.Color;
    return Output;
}

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