解决Unity urp级联阴影接缝问题
作者：飞天大蟾蜍
通过从unity内部函数中抽几个出来改造，强制取某个裁切球的级联阴影映射，通过案例给大家详细介绍，文中给出了完整的urp shader代码，对Unity级联阴影知识感兴趣的朋友一起看看吧
试了一下unity自带的阴影,发现有接缝问题,
上网找了一些解决方案,都非常庞大,
基本是要自己处理级联阴影
看了urp的build-in之后,想了一个比较暗黑的方式,简单处理一下,运行对比图如下,
左边是unity自带的级联阴影效果,右边是平滑后的级联阴影
思路比较简单,从unity内部函数中抽几个出来改造
计算当前像素点(世界坐标)位于哪个裁切球,代码如下:
强制取某个裁切球的级联阴影映射,代码如下:
本案例只处理第一个裁切球与第二个裁切球过渡效果,
其它的裁切球离摄像机比较远,处不处理影响不大,如果要处理,方法也是相同的
混合两个解析度的阴影代码如下
其它urp管线需要用到的pass DepthOnly ShadowCaster就不说明了,照抄就可以了,以便物体本身也能生成阴影
以下贴出完整的urp shader代码
Shader "lsc/csm_shader"
{
Properties
{
_MainTex("Texture", 2D) = "white" {}
}
SubShader
{
LOD 100
Tags{"RenderType" = "Opaque" "RenderPipeline" = "UniversalPipeline" "UniversalMaterialType" = "Lit" "IgnoreProjector" = "True" "ShaderModel" = "2.0"}
Pass
{
Name "ForwardLit"
Tags{"LightMode" = "UniversalForward"}
HLSLPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma exclude_renderers gles gles3 glcore
#pragma target 4.5
#pragma multi_compile _ _MAIN_LIGHT_SHADOWS
#pragma multi_compile _ _MAIN_LIGHT_SHADOWS_CASCADE
#pragma multi_compile_fragment _ _ADDITIONAL_LIGHT_SHADOWS
#pragma multi_compile_fragment _ _SHADOWS_SOFT
#pragma vertex LitPassVertex
#pragma fragment LitPassFragment
#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"
struct appdata
{
float4 vertex : POSITION;
float2 uv : TEXCOORD0;
float3 normal : NORMAL;
};
struct v2f
{
float2 uv : TEXCOORD0;
float4 vertex : SV_POSITION;
float3 normal : TEXCOORD2;
float3 world_pos : TEXCOORD3;
};
sampler2D _MainTex;
float4 _MainTex_ST;
v2f vert(appdata v)
{
v2f o;
VertexPositionInputs vertexInput = GetVertexPositionInputs(v.vertex.xyz);
o.vertex = vertexInput.positionCS;;
o.uv = TRANSFORM_TEX(v.uv, _MainTex);
o.normal = v.normal;
o.world_pos = vertexInput.positionWS;
return o;
}
//常规的计算csm纹理映射函数
//unity把所有的级联阴影刷在一个深度纹理
//通过切换shadow coord的方式取不同解析度的光源深度纹理
//每个解析度区间是用裁切球的方式
float4 anhei_TransformWorldToShadowCoord(float3 positionWS)
{
half cascadeIndex = ComputeCascadeIndex(positionWS);
float4 shadowCoord = mul(_MainLightWorldToShadow[cascadeIndex], float4(positionWS, 1.0));
return float4(shadowCoord.xyz, cascadeIndex);
}
//自定义直接指定取某个区间段级联阴影
float4 anhei_TransformWorldToShadowCoord2(int idx, float3 positionWS)
{
half cascadeIndex = idx;
float4 shadowCoord = mul(_MainLightWorldToShadow[cascadeIndex], float4(positionWS, 1.0));
return float4(shadowCoord.xyz, cascadeIndex);
}
//常规计算当前像素点(世界坐标)处于哪个裁切球
half anhei_ComputeCascadeIndex(float3 positionWS)
{
float3 fromCenter0 = positionWS - _CascadeShadowSplitSpheres0.xyz;
float3 fromCenter1 = positionWS - _CascadeShadowSplitSpheres1.xyz;
float3 fromCenter2 = positionWS - _CascadeShadowSplitSpheres2.xyz;
float3 fromCenter3 = positionWS - _CascadeShadowSplitSpheres3.xyz;
float4 distances2 = float4(dot(fromCenter0, fromCenter0), dot(fromCenter1, fromCenter1), dot(fromCenter2, fromCenter2), dot(fromCenter3, fromCenter3));
half4 weights = half4(distances2 < _CascadeShadowSplitSphereRadii);
weights.yzw = saturate(weights.yzw - weights.xyz);
return 4 - dot(weights, half4(4, 3, 2, 1));
}
float4 frag(v2f i) : SV_Target
{
// sample the texture
float4 col = tex2D(_MainTex, i.uv);
float3 nml = normalize(i.normal.xyz);
int cas_idx_1 = anhei_ComputeCascadeIndex(i.world_pos);
Light light_1;
Light light_0;
half shadow_mix = 1.0f;
float mix_fact = 0;
if (cas_idx_1 == 0)//只处理第一个裁切球,其它裁切球的太远了,在画面上可能看不见
{
float4 shadow_coord0 = anhei_TransformWorldToShadowCoord2(0, i.world_pos);
light_0 = GetMainLight(shadow_coord0);
float4 shadow_coord1 = anhei_TransformWorldToShadowCoord2(1, i.world_pos);
light_1 = GetMainLight(shadow_coord1);
shadow_mix = light_1.shadowAttenuation;
//离第一个裁切球心距离
float3 fromCenter0 = i.world_pos - _CascadeShadowSplitSpheres0.xyz;
float3 first_sphere_dis = length(fromCenter0);
//第一个裁切球的半径
float first_sphere_rad = sqrt(_CascadeShadowSplitSphereRadii.x);
//做一个简单的插值
mix_fact = clamp((first_sphere_dis) / (first_sphere_rad / 1.0f), 0.0f, 1.0f);
shadow_mix = light_0.shadowAttenuation* (1 - mix_fact) + light_1.shadowAttenuation * mix_fact;
}
else
{
float4 shadow_coord1 = anhei_TransformWorldToShadowCoord2(1, i.world_pos);
light_1 = GetMainLight(shadow_coord1);
shadow_mix = light_1.shadowAttenuation;
}
col.rgb = shadow_mix * col.rgb;
return col;
}
ENDHLSL
}
// ShadowCaster 将物体写入光源的深度纹理
// 使用自定义的shadow caster, urp会从光源处拍摄场影
pass
{
Tags{ "LightMode" = "ShadowCaster" }
HLSLPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"
struct appdata
{
float4 vertex : POSITION;
float3 normal : NORMAL;
};
struct v2f
{
float4 pos : SV_POSITION;
};
sampler2D _MainTex;
float4 _MainTex_ST;
float3 _LightDirection;
v2f vert(appdata v)
{
v2f o;
float3 world_pos = TransformObjectToWorld(v.vertex);
float3 world_nml = TransformObjectToWorldNormal(v.normal);
o.pos = TransformWorldToHClip(ApplyShadowBias(world_pos, world_nml, _LightDirection));
return o;
}
float4 frag(v2f i) : SV_Target
{
float4 color;
color.xyz = float3(0.0, 0.0, 0.0);
return color;
}
ENDHLSL
}
// DepthOnly 直接使用内置hlsl代码
Pass
{
Name "DepthOnly"
Tags{"LightMode" = "DepthOnly"}
ZWrite On
ColorMask 0
Cull[_Cull]
HLSLPROGRAM
#pragma exclude_renderers gles gles3 glcore
#pragma target 4.5
#pragma vertex DepthOnlyVertex
#pragma fragment DepthOnlyFragment
// -------------------------------------
// Material Keywords
#pragma shader_feature_local_fragment _ALPHATEST_ON
#pragma shader_feature_local_fragment _SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A
//--------------------------------------
// GPU Instancing
#pragma multi_compile_instancing
#pragma multi_compile _ DOTS_INSTANCING_ON
#include "Packages/com.unity.render-pipelines.universal/Shaders/LitInput.hlsl"
#include "Packages/com.unity.render-pipelines.universal/Shaders/DepthOnlyPass.hlsl"
ENDHLSL
}
}
}
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