你如何在着色器中编写z-depth？

此着色器(末尾的代码)使用光线匹配来渲染过程几何:

但是,在图像(上图)中,背景中的立方体应该部分遮挡粉红色的固体; 不是因为这个:

  struct fragmentOutput {
    float4 color : SV_Target;
    float zvalue : SV_Depth;
  };

  fragmentOutput frag(fragmentInput i) {
    fragmentOutput o;
    ...
    o.zvalue = IF(output[1] > 0, 0, 1);
  }

但是,我不能在我的生活中弄清楚如何在这里正确生成深度值,正确地允许光线移动的实体隐藏/不掩盖场景中的其他几何体.

我知道这是可能的,因为这里有一个有效的例子:https://github.com/i-saint/RaymarchingOnUnity5(相关的日语博客http://i-saint.hatenablog.com/)

然而,它是日语,很大程度上没有文档,而且非常复杂.

我正在寻找同样的东西的极简化版本,从中可以构建.

在着色器中我正在使用片段程序行:

float2 output = march_raycast(i.worldpos, i.viewdir, _far, _step);

将四边形上的输入点p映射到需要相机(此着色器附加到其上)的输出浮点2(密度,距离),其中距离是从程序表面上的四边形到"点"的距离.

问题是,如何以任何有用的方式将其映射到深度缓冲区？

完整的着色器在这里,使用它,创建一个球体在0,0,0,大小至少为50的新场景,并为其指定着色器:

Shader "Shaders/Raymarching/BasicMarch" {
  Properties {
    _sun ("Sun", Vector) = (0, 0, 0, 0)
    _far ("Far Depth Value", Float) = 20
    _edgeFuzz ("Edge fuzziness", Range(1, 20)) = 1.0
    _lightStep ("Light step", Range(0.1, 5)) = 1.0
    _step ("Raycast step", Range(0.1, 5)) = 1.0
    _dark ("Dark value", Color) = (0, 0, 0, 0)
    _light ("Light Value", Color) = (1, 1, 1, 1)
    [Toggle] _debugDepth ("Display depth field", Float) = 0
    [Toggle] _debugLight ("Display light field", Float) = 0
  }
  SubShader {
    Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
    Blend SrcAlpha OneMinusSrcAlpha
    Pass {
      CGPROGRAM

      #pragma vertex vert
      #pragma fragment frag
      #pragma target 3.0

      #include "UnityCG.cginc"
      #include "UnityLightingCommon.cginc" // for _LightColor0
      #define IF(a, b, c) lerp(b, c, step((fixed) (a), 0));

      uniform float _far;
      uniform float _lightStep;
      uniform float3 _sun;
      uniform float4 _light;
      uniform float4 _dark;
      uniform float _debugDepth;
      uniform float _debugLight;
      uniform float _edgeFuzz;
      uniform float _step;

      /**
       * Sphere at origin c, size s
       * @param center_ The center of the sphere
       * @param radius_ The radius of the sphere
       * @param point_ The point to check
       */
      float geom_soft_sphere(float3 center_, float radius_, float3 point_) {
        float rtn = distance(center_, point_);
        return IF(rtn < radius_, (radius_ - rtn) / radius_ / _edgeFuzz, 0);
      }

      /**
       * A rectoid centered at center_
       * @param center_ The center of the cube
       * @param halfsize_ The halfsize of the cube in each direction
       */
      float geom_rectoid(float3 center_, float3 halfsize_, float3 point_) {
        float rtn = IF((point_[0] < (center_[0] - halfsize_[0])) || (point_[0] > (center_[0] + halfsize_[0])), 0, 1);
        rtn = rtn * IF((point_[1] < (center_[1] - halfsize_[1])) || (point_[1] > (center_[1] + halfsize_[1])), 0, 1);
        rtn = rtn * IF((point_[2] < (center_[2] - halfsize_[2])) || (point_[2] > (center_[2] + halfsize_[2])), 0, 1);
        rtn = rtn * distance(point_, center_);
        float radius = length(halfsize_);
        return IF(rtn > 0, (radius - rtn) / radius / _edgeFuzz, 0);
      }

      /**
       * Calculate procedural geometry.
       * Return (0, 0, 0) for empty space.
       * @param point_ A float3; return the density of the solid at p.
       * @return The density of the procedural geometry of p.
       */
      float march_geometry(float3 point_) {
        return
          geom_rectoid(float3(0, 0, 0), float3(7, 7, 7), point_) +
          geom_soft_sphere(float3(10, 0, 0), 7, point_) +
          geom_soft_sphere(float3(-10, 0, 0), 7, point_) +
          geom_soft_sphere(float3(0, 0, 10), 7, point_) +
          geom_soft_sphere(float3(0, 0, -10), 7, point_);
      }

      /** Return a randomish value to sample step with */
      float rand(float3 seed) {
        return frac(sin(dot(seed.xyz ,float3(12.9898,78.233,45.5432))) * 43758.5453);
      }

      /**
       * March the point p along the cast path c, and return a float2
       * which is (density, depth); if the density is 0 no match was
       * found in the given depth domain.
       * @param point_ The origin point
       * @param cast_ The cast vector
       * @param max_ The maximum depth to step to
       * @param step_ The increment to step in
       * @return (denity, depth)
       */
      float2 march_raycast(float3 point_, float3 cast_, float max_, float step_) {
        float origin_ = point_;
        float depth_ = 0;
        float density_ = 0;
        int steps = floor(max_ / step_);
        for (int i = 0; (density_ <= 1) && (i < steps); ++i) {
          float3 target_ = point_ + cast_ * i * step_ + rand(point_) * cast_ * step_;
          density_ += march_geometry(target_);
          depth_ = IF((depth_ == 0) && (density_ != 0), distance(point_, target_), depth_);
        }
        density_ = IF(density_ > 1, 1, density_);
        return float2(density_, depth_);
      }

      /**
       * Simple lighting; raycast from depth point to light source, and get density on path
       * @param point_ The origin point on the render target
       * @param cast_ The original cast (ie. camera view direction)
       * @param raycast_ The result of the original raycast
       * @param max_ The max distance to cast
       * @param step_ The step increment
       */
      float2 march_lighting(float3 point_, float3 cast_, float2 raycast_, float max_, float step_) {
        float3 target_ = point_ + cast_ * raycast_[1];
        float3 lcast_ = normalize(_sun - target_);
        return march_raycast(target_, lcast_, max_, _lightStep);
      }

      struct fragmentInput {
        float4 position : SV_POSITION;
        float4 worldpos : TEXCOORD0;
        float3 viewdir : TEXCOORD1;
      };

      struct fragmentOutput {
        float4 color : SV_Target;
        float zvalue : SV_Depth;
      };

      fragmentInput vert(appdata_base i) {
        fragmentInput o;
        o.position = mul(UNITY_MATRIX_MVP, i.vertex);
        o.worldpos = mul(_Object2World, i.vertex);
        o.viewdir = -normalize(WorldSpaceViewDir(i.vertex));
        return o;
      }

      fragmentOutput frag(fragmentInput i) {
        fragmentOutput o;

        // Raycast
        float2 output = march_raycast(i.worldpos, i.viewdir, _far, _step);
        float2 light = march_lighting(i.worldpos, i.viewdir, output, _far, _step);
        float lvalue = 1.0 - light[0];
        float depth = output[1] / _far;

        // Generate fragment color
        float4 color = lerp(_light, _dark, lvalue);

        // Debugging: Depth
        float4 debug_depth = float4(depth, depth, depth, 1);
        color = IF(_debugDepth, debug_depth, color);

        // Debugging: Color
        float4 debug_light = float4(lvalue, lvalue, lvalue, 1);
        color = IF(_debugLight, debug_light, color);

        // Always apply the depth map
        color.a = output[0];

        o.zvalue = IF(output[1] > 0, 0, 1);
        o.color = IF(output[1] <= 0, 0, color);
        return o;
      }
      ENDCG
    }
  }
}

(是的,我知道它非常复杂,但要将这种着色器简化为"简单的测试用例"非常困难)

我很高兴接受任何回答,这是上面着色器的修改,允许程序实体被遮挡/模糊场景中的其他几何,就好像是'真实几何'.

-

编辑:您可以使用与raymarcher相同的深度函数在场景中的其他几何体上显式设置深度值,从而实现"工作":

...但是,我仍然无法使用"标准"着色器使其与几何体一起正常工作.仍在寻找可行的解决方案......

看看你链接到的项目,我看到的最重要的区别是他们的raycast march函数使用pass-by-reference参数来返回一个名为的片段位置ray_pos.该位置似乎位于对象空间中,因此它们使用视图投影矩阵对其进行变换以获取剪辑空间并读取深度值.

该项目还有一个compute_depth功能,但看起来很简单.

你的march_raycast函数已经在计算一个target_位置,所以你可以重构一下,应用out关键字将它返回给调用者,并在深度计算中使用它:

//get position using pass-by-ref
float3 ray_pos = i.worldpos;
float2 output = march_raycast(ray_pos, i.viewdir, _far, _step);

...

//convert position to clip space, read depth
float4 clip_pos = mul(UNITY_MATRIX_VP, float4(ray_pos, 1.0));
o.zvalue = clip_pos.z / clip_pos.w;