screen space reflection/soft alpha test/

http://www.crytek.com/cryengine/presentations/secrets-of-cryengine-3-graphics-technology

很多宝贝里面

不止题目那俩

soft alpha test不用msaa的话用后处理

screen space reflection用 ray tracing

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screen space reflection /real time local reflection

1.为每个像素计算反射vector（deferred depth and normal）这里需要normal

2.ray march along reflect vector（拿depth01）

3.depth01与sample depth检测 

4.if hit sample last frame color

看起来合适deferred shading

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screen space selt-shadow

soft shadow

contact shadow

======================

skin

http://www.iryoku.com/stare-into-the-future

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pass 0

pass 1

pass 2

blur几次 接着

pass3 composition

http://casual-effects.blogspot.com/2014/08/screen-space-ray-tracing.html

算法描述

pass0

1.计算每个pixel的reflect vector用wold normal（view关于normal的reflect）

2.沿reflect vector ray march，设step=n

3.在step那里 sample depth tex得到depthS

   在step那里可以算得 reflect方向上此点depth01

4.if depth01<depthS continue;继续迭代

5.if depth01>depthS hit,此点被场景遮挡 形成反射

    return 此点的data---uv pos iterator count hit

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下面有些问题 步长该如何确定，一共多少step

A：步长小会更精确 大会fast 取个合适的值 有个最大距离限制和最大迭代次数限制 合理设置一下 可见的反射距离

jitter为什么加进来

A：

 分层抽样stratified sampling 积分收敛和视觉效果优于均匀采样

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错的地方 fade out

屏幕外面的pix在屏幕内部发生反射的那部分图像不存在 用fade out掩饰下

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ray marching

sphere marching for sdf 每个黑点那里存了distance to surface

cone tracing

cone 就是这个cone

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http://casual-effects.blogspot.com/2014/08/screen-space-ray-tracing.html

代码

github postprocessing stack v2

https://github.com/Unity-Technologies/PostProcessing

使用manual

https://docs.unity3d.com/Manual/PostProcessing-ScreenSpaceReflection.html

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这张算法图说的很详细了 和我理解的是一致的

https://gizmosandgames.com/2017/01/17/screen-space-reflections/

算uv reflection上step那次的uv

// Center of ray through pixel
t2 = min(tMax.x, tMax.y);
average = refl_dir * (t1 + t2) * 0.5f;
t1 = t2;

// Calculating the eye vector for the current pixel
float u = (pos.x + 0.5f + average.x) / width - 0.5f;
float v = (pos.y + 0.5f + average.y) / height - 0.5f;
cam_ray_dir = float3(u, v * aspect, -ratio);

// Compare ray depth to world depth and end if ray has gone behind image
depth_travelled = intersection(starting_world_pos, float3(0,0,0), refl_dir, cam_ray_dir);
ray_depth = starting_world_pos.z + depth_travelled * refl_dir.z;
if (!src.bounds.inside(pixel_x, pixel_y) || ray_depth <= world_pos(pixel_x, pixel_y, 2))
  break;
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http://roar11.com/2015/07/screen-space-glossy-reflections/