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Atmospheric Scattering XNA 4.0


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#1 montify   Members   -  Reputation: 395

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Posted 30 November 2012 - 11:34 AM

Hello

Anyone out there who could help me..

SpaceToSky Shader...

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float4x4 World; 
float4x4 View; 
float4x4 Projection; 
float seaLevel; 

float Km = 0.0025f;
float Kr = 0.0015f;
float ESun = 20.0f;

float3 v3InvWavelength = float3(
  1.0f / pow(0.650f, 4),
  1.0f / pow(0.570f, 4),
  1.0f / pow(0.475f, 4)
);


// The number of sample points taken along the ray
static const int nSamples = 2;
static const float fSamples = (float)nSamples;
// Gravity
static const float g  = -0.99f;
static const float g2 =  0.81f;

// Shader Constants
float3 v3CameraPos;   // The camera's current position
float3 v3LightPos;   // The direction vector to the light source

//float3 v3InvWavelength;  // 1 / pow(wavelength, 4) for the red, green, and blue channels
float fCameraHeight;  // The camera's current height
float fCameraHeight2;  // fCameraHeight^2


float fOuterRadius= 1.4f;   // The outer (atmosphere) radius
float fOuterRadius2 = (1.4f * 1.4f);  // fOuterRadius^2
float fInnerRadius = 1.0f;   // The inner (planetary) radius
float fInnerRadius2 = (1.0f * 1.0f);  // fInnerRadius^2

float fKrESun = (0.0015f * 10.0f);  // Kr * ESun
float fKmESun = (0.0025f * 10.0f);;  // Km * ESun

float fKr4PI = 0.0015f * 4.0f * 3.14159265; 
float fKm4PI = 0.0025f * 4 * 3.14159265;   // Km * 4 * PI

float fScaleDepth = 0.25f;   // The scale depth (the altitude at which the average atmospheric density is found)
float fInvScaleDepth = 1.0f / 0.25f;  // 1 / fScaleDepth
float fScale = 1.0f / (1.4f - 1.0f);
float fScaleOverScaleDepth = (1.0f)  / ( 1.0f / 0.25f); // fScale / fScaleDepth

	float scale(float fCos)
	{
		float x = 1.0 - fCos;
		return fScaleDepth * exp(-0.00287 + x*(0.459 + x*(3.83 + x*(-6.80 + x*5.25))));
	}
	// Calculates the Mie phase function
	float getMiePhase(float fCos, float fCos2, float g, float g2)
	{
		return 1.5 * ((1.0 - g2) / (2.0 + g2)) * (1.0 + fCos2) / pow(abs(1.0 + g2 - 2.0*g*fCos), 1.5);
	}

	// Calculates the Rayleigh phase function
	float getRayleighPhase(float fCos2)
	{
		//return 1.0;
		return 0.75 + 0.75*fCos2;
	}

	// Returns the near intersection point of a line and a sphere
	float getNearIntersection(float3 v3Pos, float3 v3Ray, float fDistance2, float fRadius2)
	{
		float B = 2.0 * dot(v3Pos, v3Ray);
		float C = fDistance2 - fRadius2;
		float fDet = max(0.0, B*B - 4.0 * C);
		return 0.5 * (-B - sqrt(fDet));
	}

	// Returns the far intersection point of a line and a sphere
	float getFarIntersection(float3 v3Pos, float3 v3Ray, float fDistance2, float fRadius2)
	{
		float B = 2.0 * dot(v3Pos, v3Ray);
		float C = fDistance2 - fRadius2;
		float fDet = max(0.0, B*B - 4.0 * C);
		return 0.5 * (-B + sqrt(fDet));
	}

	struct VertexShaderInput 
	{ 
		float4 Position : POSITION0; 
		float3 PositionWS : TEXCOORD0;
	}; 

	struct VertexShaderOutput
	{ 
		float4 Position : POSITION0; 
		float3 PositionWS : TEXCOORD0;
	}; 



//#############  VERTEX SHADER  #############
VertexShaderOutput VertexShaderFunction(VertexShaderInput input) 
{ 
	VertexShaderInput output; 
	
	output.PositionWS = input.Position;
	
	float4 worldPosition = mul(input.Position, World); 
	worldPosition = float4( normalize(worldPosition.xyz) * 6918.75f, 1); 

	
	float4 viewPosition = mul(worldPosition, View); 
	output.Position = mul(viewPosition, Projection); 
	return output; 
} 


//#############  PIXEL SHADER  #############
float4 PixelShaderFunction(VertexShaderOutput input) : COLOR0 
{ 

	// Get the ray from the camera to the vertex and its length (which is the far point of the ray passing through the atmosphere)
	float3 v3Pos = input.PositionWS;
	float3 v3Ray = v3Pos - v3CameraPos;
	float fFar = length(v3Ray);
	v3Ray /= fFar;

	// Calculate the closest intersection of the ray with the outer atmosphere (which is the near point of the ray passing through the atmosphere)
	float fNear = getNearIntersection(v3CameraPos, v3Ray, fCameraHeight2, fOuterRadius2);

	// Calculate the ray's start and end positions in the atmosphere, then calculate its scattering offset
	float3 v3Start = v3CameraPos + v3Ray * fNear;
	fFar -= fNear;
	float fStartAngle = dot(v3Ray, v3Start) / fOuterRadius;
	float fStartDepth = exp(-fInvScaleDepth);
	float fStartOffset = fStartDepth*scale(fStartAngle);

	// Initialize the scattering loop variables
	float fSampleLength = fFar / fSamples;
	float fScaledLength = fSampleLength * fScale;
	float3 v3SampleRay = v3Ray * fSampleLength;
	float3 v3SamplePoint = v3Start + v3SampleRay * 0.5;

	// Now loop through the sample rays
	float3 v3FrontColor = float3(0.0, 0.0, 0.0);
	for(int i=0; i<nSamples; i++)
	{
	  float fHeight = length(v3SamplePoint);
	  float fDepth = exp(fScaleOverScaleDepth * (fInnerRadius - fHeight));
	  float fLightAngle = dot(v3LightPos, v3SamplePoint) / fHeight;
	  float fCameraAngle = dot(v3Ray, v3SamplePoint) / fHeight; 
	  float fScatter = (fStartOffset + fDepth*(scale(fLightAngle) - scale(fCameraAngle)));
	  float3 v3Attenuate = exp(-fScatter * (v3InvWavelength * fKr4PI + fKm4PI));
	  v3FrontColor += v3Attenuate * (fDepth * fScaledLength);
	  v3SamplePoint += v3SampleRay;
	}

	// Finally, scale the Mie and Rayleigh colors and set up the varying variables for the pixel shader
	float3 c0 = v3FrontColor * (v3InvWavelength * fKrESun);
	float3 c1 = v3FrontColor * fKmESun;
	float3 v3Direction = v3CameraPos - v3Pos;
	float fCos = dot(v3LightPos, v3Direction) / length(v3Direction);
	float fCos2 = fCos*fCos;
	float3 color = getRayleighPhase(fCos2) * c0 + getMiePhase(fCos, fCos2, g, g2) * c1;
	float4 AtmoColor = float4(color, color.b);
	return AtmoColor;
} 


//#############  Technik  #############
technique Technique1 
{ 
	pass Pass1 
	{ 
		CullMode = ccw;
		VertexShader = compile vs_3_0 VertexShaderFunction(); 
		PixelShader = compile ps_3_0 PixelShaderFunction(); 
	} 
}

And here the Sphere.cs:


 public class ScatteringSphere
    {
        private GraphicsDevice device;
        private VertexBuffer vb;
        private IndexBuffer ib;
        private Effect effect;
        private static int size = 128;
        Matrix[] rotation = new Matrix[6];
        Vector3 lightPos;

        public ScatteringSphere(GraphicsDevice device)
        {
            this.device = device;

            effect = Manager.cManager.Load<Effect>("Effekte\\SpaceToSky");
            CreateSphere();

            rotation[0] = Matrix.CreateRotationX(MathHelper.ToRadians(180)) * Matrix.CreateTranslation(Vector3.Down);
            rotation[1] = Matrix.CreateTranslation(Vector3.Up);
            rotation[2] = Matrix.CreateRotationX(MathHelper.ToRadians(90)) * Matrix.CreateTranslation(Vector3.Backward);
            rotation[3] = Matrix.CreateRotationX(MathHelper.ToRadians(270)) * Matrix.CreateTranslation(Vector3.Forward);
            rotation[4] = Matrix.CreateRotationZ(MathHelper.ToRadians(270)) * Matrix.CreateTranslation(Vector3.Right);
            rotation[5] = Matrix.CreateRotationZ(MathHelper.ToRadians(90)) * Matrix.CreateTranslation(Vector3.Left);

        }

        private void CreateSphere()
        {
            VertexPositionColor[] vertices = new VertexPositionColor[size * size];
            for (int z = 0; z < size; z++)
                for (int x = 0; x < size; x++)
                    vertices[x + z * size] = new VertexPositionColor(new Vector3(MathHelper.Lerp(-1, 1, (float)x / (size - 1)), 0, MathHelper.Lerp(-1, 1, (float)z / (size - 1))), Color.Aquamarine);

            vb = new VertexBuffer(device, typeof(VertexPositionColor), size * size, BufferUsage.WriteOnly);
            vb.SetData<VertexPositionColor>(vertices);

            ushort[] indices = new ushort[(size - 1) * (size - 1) * 6];
            int i = 0;
            for (int z = 0; z < size - 1; z++)
                for (int x = 0; x < size - 1; x++)
                {
                    ushort upperleft = (ushort)(z * size + x);
                    ushort upperright = (ushort)(upperleft + 1);
                    ushort lowerleft = (ushort)(upperleft + size);
                    ushort lowerright = (ushort)(lowerleft + 1);

                    indices[i++] = upperleft;
                    indices[i++] = upperright;
                    indices[i++] = lowerleft;

                    indices[i++] = lowerleft;
                    indices[i++] = upperright;
                    indices[i++] = lowerright;
                }

            ib = new IndexBuffer(device, IndexElementSize.SixteenBits, indices.Length, BufferUsage.WriteOnly);
            ib.SetData<ushort>(indices);



        }

        public void Draw(FreeCam cam)
        {
            device.SetVertexBuffer(vb);
            device.Indices = ib;

            lightPos = new Vector3(0.5f, 0.5f, -0.5f);
            lightPos.Normalize();

            effect.Parameters["seaLevel"].SetValue(6750);
            effect.Parameters["View"].SetValue(Manager.cam.View);
            effect.Parameters["Projection"].SetValue(Manager.cam.Projection);
            effect.Parameters["v3CameraPos"].SetValue(Manager.cam.Position);
            effect.Parameters["v3LightPos"].SetValue(lightPos);
            effect.Parameters["fCameraHeight"].SetValue(Manager.cam.Position.Length());
            effect.Parameters["fCameraHeight2"].SetValue(Manager.cam.Position.LengthSquared());




            effect.Parameters["World"].SetValue(rotation[0]);
            foreach (EffectPass pass in effect.CurrentTechnique.Passes)
            {
                pass.Apply();
                device.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, size * size, 0, (size - 1) * (size - 1) * 6 / 3);
            }

            effect.Parameters["World"].SetValue(rotation[1]);
            foreach (EffectPass pass in effect.CurrentTechnique.Passes)
            {
                pass.Apply();
                device.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, size * size, 0, (size - 1) * (size - 1) * 6 / 3);
            }

            effect.Parameters["World"].SetValue(rotation[2]);
            foreach (EffectPass pass in effect.CurrentTechnique.Passes)
            {
                pass.Apply();
                device.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, size * size, 0, (size - 1) * (size - 1) * 6 / 3);
            }

            effect.Parameters["World"].SetValue(rotation[3]);
            foreach (EffectPass pass in effect.CurrentTechnique.Passes)
            {
                pass.Apply();
                device.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, size * size, 0, (size - 1) * (size - 1) * 6 / 3);
            }

            effect.Parameters["World"].SetValue(rotation[4]);
            foreach (EffectPass pass in effect.CurrentTechnique.Passes)
            {
                pass.Apply();
                device.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, size * size, 0, (size - 1) * (size - 1) * 6 / 3);
            }

            effect.Parameters["World"].SetValue(rotation[5]);
            foreach (EffectPass pass in effect.CurrentTechnique.Passes)
            {
                pass.Apply();
                device.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, size * size, 0, (size - 1) * (size - 1) * 6 / 3);

            }

        }



    } 

AA

Edited by montify, 30 November 2012 - 12:54 PM.


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#2 montify   Members   -  Reputation: 395

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Posted 03 December 2012 - 04:34 PM

Job Done






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