体积雾 global fog unity 及改进

https://github.com/keijiro/KinoFog

lighting box 2.7.2

halfspace fog 相机位于一个位置 这个位置可以在fog volumn里面或者外面  雾开始的地方就是文中的plane

http://www.terathon.com/lengyel/Lengyel-UnifiedFog.pdf

这个fog volume可以从中间某个位置height 这个平面产生雾 远近浓度通过depth深度计算

还可以定义雾密度

    // Applies one of standard fog formulas, given fog coordinate (i.e. distance)

    half ComputeFogFactor (float coord)

    {

        float fogFac = 0.0;

        if (_SceneFogMode.x == ) // linear

        {

            // factor = (end-z)/(end-start) = z * (-1/(end-start)) + (end/(end-start))

            fogFac = coord * _SceneFogParams.z + _SceneFogParams.w;

        }

        if (_SceneFogMode.x == ) // exp

        {

            // factor = exp(-density*z)

            fogFac = _SceneFogParams.y * coord; fogFac = exp2(-fogFac);

        }

        if (_SceneFogMode.x == ) // exp2

        {

            // factor = exp(-(density*z)^2)

            fogFac = _SceneFogParams.x * coord; fogFac = exp2(-fogFac*fogFac);

        }

        return saturate(fogFac);

    }

    // Distance-based fog

    float ComputeDistance (float3 camDir, float zdepth)

    {

        float dist;

        if (_SceneFogMode.y == )

            dist = length(camDir);

        else

            dist = zdepth * _ProjectionParams.z;

        // Built-in fog starts at near plane, so match that by

        // subtracting the near value. Not a perfect approximation

        // if near plane is very large, but good enough.

        dist -= _ProjectionParams.y;

        return dist;

    }

     float ComputeHalfSpace (float3 wsDir)

    {

        float3 wpos = _CameraWS + wsDir;

        float FH = _HeightParams.x;

        float3 C = _CameraWS;

        float3 V = wsDir;

        float3 P = wpos;

        float3 aV = _HeightParams.w * V;

        float FdotC = _HeightParams.y;

        float k = _HeightParams.z;

        float FdotP = P.y-FH;

        float FdotV = wsDir.y;

        float c1 = k * (FdotP + FdotC);

        float c2 = (-*k) * FdotP;

        float g = min(c2, 0.0);

        g = -length(aV) * (c1 - g * g / abs(FdotV+1.0e-5f));

        return g;

    }

FdocC = camPos.y-height.value;      height  就是halfplane所定义的高度 plane法线垂直向上

       // Calculate vectors towards frustum corners.

            var cam = GetComponent<Camera>();

            var camtr = cam.transform;

            var camNear = cam.nearClipPlane;

            var camFar = cam.farClipPlane;

            var tanHalfFov = Mathf.Tan(cam.fieldOfView * Mathf.Deg2Rad / );

            var toRight = camtr.right * camNear * tanHalfFov * cam.aspect;

            var toTop = camtr.up * camNear * tanHalfFov;

            var v_tl = camtr.forward * camNear - toRight + toTop;

            var v_tr = camtr.forward * camNear + toRight + toTop;

            var v_br = camtr.forward * camNear + toRight - toTop;

            var v_bl = camtr.forward * camNear - toRight - toTop;

            var v_s = v_tl.magnitude * camFar / camNear;

            // Draw screen quad.

            RenderTexture.active = destination;

            _material.SetTexture("_MainTex", source);

            _material.SetPass();

            GL.PushMatrix();

            GL.LoadOrtho();

            GL.Begin(GL.QUADS);

            GL.MultiTexCoord2(, , );

            GL.MultiTexCoord(, v_bl.normalized * v_s);

            GL.Vertex3(, , 0.1f);

            GL.MultiTexCoord2(, , );

            GL.MultiTexCoord(, v_br.normalized * v_s);

            GL.Vertex3(, , 0.1f);

            GL.MultiTexCoord2(, , );

            GL.MultiTexCoord(, v_tr.normalized * v_s);

            GL.Vertex3(, , 0.1f);

            GL.MultiTexCoord2(, , );

            GL.MultiTexCoord(, v_tl.normalized * v_s);

            GL.Vertex3(, , 0.1f);

            GL.End();

            GL.PopMatrix();

这里是用了一个quard我做到用trangle了

要铭记一点 quard 和trangle的插值结果 顶多数据传对了 插值是一样的 没有差别 因为都是线性的 这个问题我想了好几个小时！

uv 和pos肯定是一样的 dir也是一样的 因为也是线性的

这意味着我接下来可以做大面积优化了 好开心

mg你太棒了 这个小故事告诉我们代码要每一行都看懂 不要再像黑盒那样抄了

Vector3 topLeft3 = topLeft*2-bottomLeft;//2

Vector3 bottomRight3 = bottomRight*2 -bottomLeft;//1

Vector3 topRight3= bottomRight3+topLetf3;//0

这里因为scale过到farplane不能在原始那个nearplane的数据直接3x