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Article : Realistic Soft Edged Water In XNA

The reflection looks nice, but the edges are all blue. What we need is the refraction texture, which is set up in much the same way as the scene depth, except we do not need our own shader.

Add a third render target to the game class:

private RenderTarget2D sceneColor;

Again, initialize it in LoadContent(), but instead of using the screen width and height, use half that size since we do not need as much detail.

sceneColor = new RenderTarget2D(GraphicsDevice, width / 2, height / 2, 1, SurfaceFormat.Color, RenderTargetUsage.DiscardContents);

Now we can draw to it, place this before the DrawReflection() call:

GraphicsDevice.SetRenderTarget(0, this.sceneColor);
GraphicsDevice.Clear(ClearOptions.DepthBuffer | ClearOptions.Target, Color.CornflowerBlue, 1f, 0);
this.DrawTerrain(null, ref view, ref projection);

Also, just like reflection, we need to pass the texture to the PlanarWater Draw method. Change the PlanarWater Draw method to:

public void Draw(GraphicsDevice device, Texture2D sceneDepth, Texture2D waterReflection, Texture2D sceneColor,
                 Matrix waterViewProjection, Matrix view, Matrix projection)
{
    device.VertexDeclaration = this.PlaneVD;
    device.Vertices[0].SetSource(this.PlaneVB, 0, VertexPositionTexture.SizeInBytes);
    device.Indices = null;

    device.Textures[0] = sceneDepth;
    device.Textures[1] = waterReflection;
    device.Textures[2] = sceneColor;

    for (int i = 0; i < 3; i++)
    {
        device.SamplerStates[i].AddressU = TextureAddressMode.Clamp;
        device.SamplerStates[i].AddressV = TextureAddressMode.Clamp;
    }

    device.SamplerStates[0].MinFilter = TextureFilter.Point;
    device.SamplerStates[0].MagFilter = TextureFilter.Point;
    device.SamplerStates[0].MipFilter = TextureFilter.Point;

    RenderState renderState = device.RenderState;

    renderState.DepthBufferEnable = true;
    renderState.AlphaTestEnable = false;
    renderState.AlphaBlendEnable = false;

    this.WaterEffect.Begin();

    this.WaterEffect.Parameters["World"].SetValue(PlanarWater.World);
    this.WaterEffect.Parameters["View"].SetValue(view);
    this.WaterEffect.Parameters["Projection"].SetValue(projection);
    this.WaterEffect.Parameters["WaterViewProjection"].SetValue(waterViewProjection);

    this.WaterEffect.Techniques[0].Passes[0].Begin();

    const int primitiveCount = 2 * (TesselationN1*TesselationN1);
    device.DrawPrimitives(PrimitiveType.TriangleList, 0, primitiveCount);

    this.WaterEffect.Techniques[0].Passes[0].End();
    this.WaterEffect.End();

    device.Textures[0] = null;
    device.Textures[1] = null;
    device.Textures[2] = null;

    for (int i = 0; i < 3; i++)
    {
        device.SamplerStates[i].AddressU = TextureAddressMode.Wrap;
        device.SamplerStates[i].AddressV = TextureAddressMode.Wrap;
    }

    device.SamplerStates[0].MinFilter = TextureFilter.Linear;
    device.SamplerStates[0].MagFilter = TextureFilter.Linear;
    device.SamplerStates[0].MipFilter = TextureFilter.Linear;
}

…and update the call to it:

this.water.Draw(graphics.GraphicsDevice, this.sceneDepth.GetTexture(), this.waterReflection.GetTexture(), this.sceneColor.GetTexture(), reflectionViewProjection, view, projection);

Now we are ready to use it in the shader. Add a third sampler for refraction in water.fx:

sampler2D RefractionSampler : register(s2);

Now we can read the refraction texture instead of using a blue color.

Change:

float3 refraction = float3(0, 0, 1);

To:

float3 refraction = tex2D(RefractionSampler, screenTexCoords).rgb;

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