前言
前面4章完成了波浪动画、上色、岸边泡沫的生成。本章梳理水底的焦散模拟。
焦散模拟
我们可以使用类似的水纹的贴图作色散分离，或者直接使用分离的三通道贴图。
下面的代码设置了宏_DISPERSION_ON，如果是三通道分离贴图，则调用_getDispersion函数
real4 _getCausticReults(float2 uv){uv = uv / _CausticsScale;float speed = _Time.y * _CausticsSpeed * 0.1;#ifdef _DISPERSION_ONfloat3 channel_offset = _Channel_Offset.xyz*0.01;real4 caustics1 = _getDispersion(_CausticsTex, sampler_CausticsTex, uv+speed,channel_offset );real4 caustics2 = _getDispersion(_CausticsTex, sampler_CausticsTex, speed*0.8-uv,channel_offset );#elsereal4 caustics1 = SAMPLE_TEXTURE2D(_CausticsTex, sampler_CausticsTex, uv+speed);real4 caustics2 = SAMPLE_TEXTURE2D(_CausticsTex, sampler_CausticsTex, speed*0.8-uv);#endifreturn real4(min(caustics1, caustics2));}
_getDispersion函数
real4 _getDispersion(Texture2D tex,SamplerState _sampler,float2 uv,float3 channel_offset){float r = SAMPLE_TEXTURE2D(tex, _sampler, uv+channel_offset.x).r;float g = SAMPLE_TEXTURE2D(tex, _sampler, uv+channel_offset.y).g;float b = SAMPLE_TEXTURE2D(tex, _sampler, uv+channel_offset.b).b;return real4(r, g, b, 1);}
左边是未色散的情况，右边是色散的情况
为了让波纹贴附在水底，我们使用第一章从深度图重建的世界坐标来采样贴图
最后代码如下，我们还利用了第一章的RawDepth来建立焦散的maskcausticsMask
real4 frag(v2f i) : SV_TARGET{// =========Get necessity=========== //float3 PosW = i.posW;float3 normalW = i.normalW;float3 viewW = i.viewDirW;float4 screenPos = i.scrPos / i.scrPos.w;// screenPos.z = (UNITY_NEAR_CLIP_VALUE >=0)?screenPos.z:screenPos.z* 0.5 + 0.5;float sceneRawDepth = SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, sampler_CameraDepthTexture,screenPos.xy);float3 worldPos = ComputeWorldSpacePosition(screenPos.xy, sceneRawDepth, UNITY_MATRIX_I_VP);float RawDepth = PosW.y-worldPos.y;float waterDepth = _getNewDepthMask(RawDepth, _DepthRange);float causticsMask = _getNewDepthMask(RawDepth, _CausticsRange);// =========Foam=========== //float FoamDepth = smoothstep(_FoamBlend, 1, RawDepth);float wave_noise = SAMPLE_TEXTURE2D(_FoamNoiseMap, sampler_FoamNoiseMap, i.uv.xy).r* _FoamNoiseStr;real4 sinWave = _getFoamWave(RawDepth, wave_noise) * _FoamCol;// =========Fresnel=========== //real4 base_col = lerp(_DeepCol, _ShallowCol, waterDepth);float F = _getfresnelMask(normalW, viewW);base_col = lerp(base_col, _FresnelCol, F);// =========Get Normals=========== //float3 normalTS = _getNormalTS(PosW.xz);float2 uvSS = screenPos.xy;uvSS += 0.01 * normalTS * _UWDistort;real4 grab_col = SAMPLE_TEXTURE2D(_CameraOpaqueTexture, sampler_CameraOpaqueTexture, uvSS);// =========Get Caustics=========== //real4 caustics_col = _getCausticReults(worldPos.xz) * _CausticsStr * causticsMask;// =========Mix Results=========== //base_col = lerp(grab_col+caustics_col, base_col, base_col.a);base_col = lerp(base_col, base_col+sinWave, sinWave.a);// return real4(caustics_col.xyz, base_col.a);return base_col;}
