ScreenSpaceShadowMask Blur推荐
- 作者:admin
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- 时间:2016年09月23日
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- 浏览:13759 次
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- 分类:厚积薄发
在移动游戏中渲染阴影时,我们通常使用低分辨率的ShadowMap来降低内存,其不足之处就是锯齿明显。对此,我们推荐大家使用Unity ScreenSpaceShadowMask Blur技术来增加阴影质量,消除锯齿感。
目的
Unity自带的阴影功能ShadowMap占用内存过大,1024 * 1024占用8MB。而我们项目内存吃紧,所以只能选用512 * 512,如下图,带有明显的锯齿感,效果差了很多。
如果您也有类似的需求,这时就可以采用 Unity ScreenSpaceShadowMask Blur。原理就是在屏幕空间里对已经投射完阴影的物体进行高斯模糊,以此来增加阴影质量,减少锯齿感。(PS:Unity提供的软阴影应该是PCF,但是效果并不明显)。
经过 ScreenSpaceShadowMask Blur后,效果如下:
具体实现步骤
一、 渲染流程
ShadowCamera的ShadowPass
->ShadowCamera 正常Pass
->BlurPass
->Main Camera Pass
->全屏片
二、详细分析
1.ShadowPass要产生ShadowMap,只需让ShadowCamera能看到投射阴影和接收阴影的物体,同时把那些阴影开关打开,Unity就会自动加入该Pass。(PS:如果物体是自己写的Vertext Fragement Shader,则需要自己加入Shadow Caster Pass,调用Unity内置即可。文件在UnityStandardShadow.cginc里)。
Shadow Camera在渲染前会统一替换成一个简单的Shader,只需包含投射跟接收阴影2个Pass即可。这样既可以减少Shader复杂度,又可以合并Draw Call。
2.正常Pass就是正常渲染阴影,比较ShadowMap与自己的深度值。我们将ShadowCamera清屏色设置成黑色,最终效果为有阴影的地方有颜色,其余地方为黑色。(颜色值会当成最后的Alpha值来处理)。
3.Blur Pass可以用CommandBuffer,也可以用OnPostRender。输入参数为ShaderCamera的Rendertarget,通过Blit来进行高斯模糊。(建议尽量少用CommandBuffer。我采用CommandBuffer,在小米1s上 RT->blurRT->RT会出现抖动现象,OnPostRender并没有。但是这两者原理应该是一样的,通过GPA查看,代码都是一样的。暂时不清楚其原因,欢迎有兴趣的朋友和我交流)。
4.Main Camera Pass 正常渲染场景。原则上渲染的物体是不会接收阴影的。
5.全屏可以通过CommandBuffer,也可以通过OnPostRender来处理。输入参数为上次经过模糊的RT值。Alpha、阴影颜色、透明度这些参数值自己写两个进行调节即可。最终渲染流程:
消耗统计
1. 内存消耗
(1) ShadowMap:512*512 2MB
(2) ShadowCamera RT 1/4屏 带16位深度
(3) Blur RT 1/4屏 不带深度
这是小米4c上的数据。
2. 渲染消耗统计
(1)多一个相机投射阴影体,接收阴影体多渲染一次;
(2)2次Blur操作;
(3)1次全屏blit操作;
主要对于带宽影响较大的物体影响较重。
总结
1.CommandBuffer 更自由,比如很多点都可以插入自定义行为,比如对ShadowMap进行操作等。虽然稳定性不佳,性能还是可以的。
2.如果一个Camera被设成RT,它会在其他相机渲染之前渲染,不受Depth影响。
相应资源
1.ShadowPass Shader
Shader "Shadow/ShadowMask" {
Properties
{
}
SubShader
{
Tags { "RenderType"="Geometry" }
Pass
{
Tags {"LightMode"="ForwardBase"}
CGPROGRAM
#pragma multi_compile_fwdbase
#pragma vertex vertForwardBase
#pragma fragment fragForwardBase
struct appdata_input
{
float4 vertex : POSITION;
};
struct v2f
{
float4 pos : SV_POSITION;
LIGHTING_COORDS(1,2)
};
v2f vertForwardBase (appdata_input v)
{
v2f o;
o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
TRANSFER_VERTEX_TO_FRAGMENT(o);
return o;
}
fixed4 fragForwardBase (v2f i) : SV_Target
{
fixed4 col = fixed4(1,0,0,1);
fixed attenuation = LIGHT_ATTENUATION(i);
col = col * (1-attenuation);
return col;
}
ENDCG
}
Pass
{
Name "ShadowCaster"
Tags { "LightMode" = "ShadowCaster" }
Fog {Mode Off}
ZWrite On ZTest LEqual Cull Off
Offset 1, 1
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma multi_compile_shadowcaster
#pragma fragmentoption ARB_precision_hint_fastest
#include "UnityCG.cginc"
struct v2f {
V2F_SHADOW_CASTER;
};
v2f vert( appdata_base v )
{
v2f o;
TRANSFER_SHADOW_CASTER(o)
return o;
}
float4 frag( v2f i ) : COLOR
{
SHADOW_CASTER_FRAGMENT(i)
}
ENDCG
}
}
}
2. 高斯模糊Shader
3. 全屏blit shader
Shader "BlitQuad1"
{
Properties
{
_MainTex("MainTexture",2D) = "white"{}
_Color("ShadowColor",Color) = (0,0,0,1)
_Intension("Intension",Float) = 0.6
}
SubShader
{
Tags { "RenderType"="Transparent" }
Blend SrcAlpha OneMinusSrcAlpha
zwrite off
Pass
{
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
struct appdata
{
float4 vertex : POSITION;
float2 uv : TEXCOORD0;
};
struct v2f
{
float2 uv : TEXCOORD0;
float4 vertex : SV_POSITION;
};
sampler2D _MainTex;
half4 _MainTex_TexelSize;
float _Intension;
fixed _Color;
v2f vert (appdata v)
{
v2f o;
o.vertex = v.vertex;
o.uv = v.uv;
return o;
}
fixed4 frag (v2f i) : SV_Target
{
half4 color = half4(1,1,1,1) * _Color;
half4 alpha = tex2D(_MainTex,i.uv);
color.a = alpha.r * _Intension;
return color;
}
ENDCG
}
}
}
C#脚本
1. ShadowCamera挂载实现 注释代码为CommandBuffer
using UnityEngine;
using UnityEngine.Rendering;
using System.Collections;
public class ShadowMask : MonoBehaviour
{
//public int maxBlurCount = 2;
public int sampleOffset = 2;
private const float UIWIDTH = 1136f;
private const int MAX_VALUE = 2048;
private int screenWidth;
private int screenHeight;
public RenderTexture renderTexture;
public RenderTexture blurRT;
//private RenderTargetIdentifier rtl;
//private RenderTargetIdentifier blurRtl;
//private CommandBuffer blurCommand;
//private CommandBuffer screenQuadCommand;
private Material material1;
private Material material2;
public Camera shadowCamera;
//public Camera mainCamera;
private int SCALE = 2;
//private int pass = 0;
//private bool hasAdd = false;
void Awake()
{
RenderTextureFormateSupportTool.GetInstance().Init();
screenWidth = Mathf.Min(Screen.width, MAX_VALUE);
screenHeight = Mathf.Min(Screen.height, MAX_VALUE);
renderTexture = RenderTextureFormateSupportTool.GetInstance().GetRenderTexture(screenWidth / SCALE, screenHeight / SCALE, 16, RenderTextureFormateSupportTool.H3DRenderTextureFormate.R8);
renderTexture.name = "RenderTexture";
blurRT = RenderTextureFormateSupportTool.GetInstance().GetRenderTexture(screenWidth / SCALE, screenHeight / SCALE,0, RenderTextureFormateSupportTool.H3DRenderTextureFormate.R8);
blurRT.name = "BlurRT";
float aspectValue = shadowCamera.aspect;
shadowCamera.targetTexture = renderTexture;
shadowCamera.aspect = aspectValue;
Shader shadowShader = Shader.Find("Shadow/ShadowMask");
shadowCamera.SetReplacementShader(shadowShader, "");
//blurCommand = new CommandBuffer();
//blurCommand.name = "BlurShadowMask";
//screenQuadCommand = new CommandBuffer();
//screenQuadCommand.name = "ScreenQuad";
//rtl = new RenderTargetIdentifier(renderTexture);
//blurRtl = new RenderTargetIdentifier(blurRT);
Shader blurShader = Shader.Find("Shadow/ShadowMaskBlur");
material1 = new Material(blurShader);
material2 = new Material(blurShader);
}
void OnPostRender()
{
material1.SetTexture("_MainTexture", renderTexture);
material1.SetInt("_Horizontal", 0);
material1.SetInt("_SampleOffset", sampleOffset);
Graphics.Blit(renderTexture, blurRT, material1);
material2.SetTexture("_MainTexture", blurRT);
material2.SetInt("_Horizontal", 1);
material2.SetInt("_SampleOffset", sampleOffset);
Graphics.Blit(blurRT, renderTexture, material2);
}
//void Update()
//{
// if (hasAdd)
// {
// blurCommand.Clear();
// }
// else
// {
// shadowCamera.AddCommandBuffer(CameraEvent.AfterEverything, blurCommand);
// hasAdd = true;
// }
// for (int i = 0; i < maxBlurCount; i++)
// {
// if (i % 2 == 0)
// {
// material1.SetTexture("_MainTexture", renderTexture);
// material1.SetInt("_Horizontal", pass % 2);
// material1.SetInt("_SampleOffset", sampleOffset);
// blurCommand.Blit(rtl, blurRtl, material1);
// }
// else
// {
// material2.SetTexture("_MainTexture", blurRT);
// material2.SetInt("_Horizontal", pass % 2);
// material2.SetInt("_SampleOffset", sampleOffset);
// blurCommand.Blit(blurRtl, blurRt2, material2);
// }
// pass++;
// }
//}
}
2.mainCamera挂载实现 全屏blit操作
using UnityEngine;
using System.Collections;
public class MainCameraTest : MonoBehaviour
{
public ShadowMask shadowMask;
public float shadowIntensity = 1f;
public Color shadowColor = Color.black;
private Material screenQuadMaterial;
private Mesh screenQuadMesh;
private Matrix4x4 matrix;
public void Start()
{
Shader screenQuadShader = Shader.Find("BlitQuad");
screenQuadMaterial = new Material(screenQuadShader);
screenQuadMaterial.SetTexture("_MainTex", shadowMask.renderTexture);
screenQuadMesh = new Mesh();
Vector3[] verts = new Vector3[4];
verts[0] = new Vector3(-1, -1, 0);
verts[1] = new Vector3(-1, 1, 0);
verts[2] = new Vector3(1, 1, 0);
verts[3] = new Vector3(1, -1, 0);
screenQuadMesh.vertices = verts;
Vector2[] uvs = new Vector2[4];
uvs[0] = new Vector2(0, 0);
uvs[1] = new Vector2(0, 1);
uvs[2] = new Vector2(1, 1);
uvs[3] = new Vector2(1, 0);
screenQuadMesh.uv = uvs;
int[] indices = new int[6];
indices[0] = 0;
indices[1] = 1;
indices[2] = 2;
indices[3] = 0;
indices[4] = 2;
indices[5] = 3;
screenQuadMesh.triangles = indices;
screenQuadMesh.Optimize();
matrix = Matrix4x4.identity;
}
void OnPostRender()
{
screenQuadMaterial.SetFloat("_Intension", shadowIntensity);
screenQuadMaterial.SetColor("_Color", shadowColor);
screenQuadMaterial.SetPass(0);
Graphics.DrawMeshNow(screenQuadMesh, matrix);
}
}
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