OSG系列文章目錄

前言

先看下效果：下雨

效果：下雪


效果：雨夾雪

🌤? Sundog Software 的 SilverLining SDK 是一個專為模擬真實天空和天氣效果而設計的高性能圖形庫，廣泛應用于飛行模擬、虛擬現實、游戲和科學可視化等領域。下面是它的核心功能介紹：

?? 3D動態云層系統
SilverLining 提供多種真實云層類型，支持動態變化和體積渲染：

積云（Cumulus）：包括 Cumulus Mediocris、Congestus、Towering Cumulus、Cumulonimbus 等，支持體積建模、云成長動畫、隨風漂移。

層云（Stratus）：適合模擬低空覆蓋的厚重云層，支持霧化和光照穿透。

卷云（Cirrus）：高空薄云，用于增強天空真實感。

沙塵暴（Sandstorm）：模擬沙塵天氣，帶有特殊的霧效和顏色。

云層支持 無限區域覆蓋、隨時間變化、隨風移動，并可通過配置文件或 API 動態控制。

降水系統（雨、雪、雨夾雪）
SilverLining 的降水系統支持三種主要天氣粒子效果：

類型 控制參數示例 特效說明
雨（RAIN） SetPrecipitation(RAIN, intensity) 模擬雨滴下落、雨絲、地面濕潤感
雪（SNOW） SetPrecipitation(SNOW, intensity) 模擬雪花飄落、雪粒旋轉、積雪感
雨夾雪（SLEET） SetPrecipitation(SLEET, intensity) 混合雨雪效果，粒子更稠密
🔧 可調參數包括：

粒子數量（如 rain-max-particles）

粒子大小（如 rain-streak-width-multiplier、snowflake-size-multiplier）

可見度影響（如 rain-visibility-multiplier）

雨絲亮度、雪花顏色、粒子速度等

📁 所有這些都可以通過 SilverLining.config 文件進行精細調節，也可以在運行時通過 API 動態修改。

🌌 天空與光照模擬
真實的太陽、月亮、星辰軌道計算

晨昏光線（Crepuscular Rays），俗稱“上帝之光”

HDR色調映射，自動調整亮度與對比度

天空顏色算法：支持 Hosek-Wilkie 模型，模擬不同大氣條件下的天空色彩

? 其他高級特效
閃電模擬：支持閃電分支、光照影響、HDR增強

云影圖：自動生成云層陰影，增強真實感

從太空看地球大氣邊緣：支持地心坐標系渲染

🧩 集成與兼容性

支持 OpenGL、DirectX、Vulkan 渲染管線

提供 C++ 和 C# API

可與 Unity、osgEarth、OpenSceneGraph 等平臺集成

跨平臺支持：Windows、Linux、macOS、iOS、Android

一、3d動態云與下雨、下雪效果不能同時出現

遇到的問題：3d動態云與下雨、下雪效果不能同時出現

二、3d動態云與下雨、下雪效果不能同時出現的原因

這是 SilverLining SDK 的一個常見“陷阱”，其實并不是你的云層消失了，而是能見度效果在起作用。
SilverLining 在啟用降水（如雨、雪、雨夾雪）時，會自動模擬真實天氣中的能見度降低。這意味著：

云層距離攝像機較遠時，會被“霧化”或“淡出”處理。

降水強度越高，能見度越低，云層越容易被遮蔽。

三、解決辦法：

🛠? 解決方法： 你可以通過修改配置文件 SilverLining.config 來調整或關閉這種能見度衰減效果：
找到SilverLining SDK安裝路徑：我的路徑是
D:\workSpace\osg\sundog\SilverLining SDK\resources\SilverLining.config

1.提高能見度倍率：雨、雪、雨夾雪

# the simulated visibility here.
rain-visibility-multiplier = 5.0# A similar fudge factor for snow visibility
snow-visibility-multiplier = 50.0# And for sleet
sleet-visibility-multiplier = 1.0

2.完全關閉能見度衰減：

enable-precipitation-visibility-effects = no
apply-fog-from-cloud-precipitation = no

添加代碼：

cumulusCongestusLayer->SetPrecipitation(SilverLining::CloudLayer::RAIN, 30.0);

🌧? 參數說明：

RAIN 是降水類型（你也可以選擇 DRY_SNOW、WET_SNOW或 SLEET）。

20.0 是降水強度，單位是毫米/小時。你可以根據需要調整這個值。
完整代碼：
頭文件

// Copyright (c) 2008-2012 Sundog Software, LLC. All rights reserved worldwide.#pragma once#include <osg/Drawable>
#include <osgViewer/Viewer>
#include "SilverLining.h"class AtmosphereReference;
class SkyDrawable;// SilverLining now supports separate cull and update methods, so we hook into OSG's cull and update
// passes using callbacks on our Drawable object.
struct SilverLiningCullCallback : public osg::Drawable::CullCallback
{SilverLiningCullCallback() : atmosphere(0) {}virtual bool cull(osg::NodeVisitor* nv, osg::Drawable* drawable, osg::RenderInfo* renderInfo) const { if (atmosphere)  {atmosphere->CullObjects();}return false; }SilverLining::Atmosphere *atmosphere;
};// Our update callback just marks our bounds dirty each frame (since they move with the camera.)
struct SilverLiningUpdateCallback : public osg::Drawable::UpdateCallback
{SilverLiningUpdateCallback() : camera(0) {}virtual void update(osg::NodeVisitor*, osg::Drawable* drawable);osg::Camera *camera;
};// We also hook in with a bounding box callback to tell OSG how big our skybox is, plus the
// atmospheric limb if applicable.
struct SilverLiningSkyComputeBoundingBoxCallback : public osg::Drawable::ComputeBoundingBoxCallback
{SilverLiningSkyComputeBoundingBoxCallback() : camera(0) {}virtual osg::BoundingBox computeBound(const osg::Drawable&) const;osg::Camera *camera;
};// The SkyDrawable wraps SilverLining to handle updates, culling, and drawing of the skybox - and works together with a CloudsDrawable
// to draw the clouds toward the end of the scene.
class SkyDrawable : public osg::Drawable
{
public:SkyDrawable();SkyDrawable(osgViewer::Viewer* view);virtual bool isSameKindAs(const Object* obj) const {return dynamic_cast<const SkyDrawable*>(obj)!=NULL;}virtual Object* cloneType() const {return new SkyDrawable();}virtual Object* clone(const osg::CopyOp& copyop) const {return new SkyDrawable();}void setSkyboxSize(double size) {_skyboxSize = size;}double getSkyboxSize() const {return _skyboxSize;}virtual void drawImplementation(osg::RenderInfo& renderInfo) const;protected:void setLighting(SilverLining::Atmosphere *atm) const;void initializeSilverLining(AtmosphereReference *ar) const;void initializeDrawable();void logCloudInfo(SilverLining::Atmosphere* atmosphere) const;osgViewer::Viewer* _view;double _skyboxSize;SilverLiningCullCallback *cullCallback;SilverLiningUpdateCallback *updateCallback;SilverLiningSkyComputeBoundingBoxCallback *computeBoundingBoxCallback;
};

實現文件：

// Copyright (c) 2008-2012 Sundog Software, LLC. All rights reserved worldwide.#include "SkyDrawable.h"
#include "SilverLining.h"
#include "AtmosphereReference.h"#include <GL/gl.h>
#include <GL/glu.h>
#include <assert.h>using namespace SilverLining;SkyDrawable::SkyDrawable(): osg::Drawable(), _view(0), _skyboxSize(100000)
{
}SkyDrawable::SkyDrawable(osgViewer::Viewer* view): osg::Drawable(), _view(view), _skyboxSize(100000)
{initializeDrawable();
}void SkyDrawable::initializeDrawable()
{setDataVariance(osg::Object::DYNAMIC);setUseVertexBufferObjects(false);setUseDisplayList(false);cullCallback = new SilverLiningCullCallback();setCullCallback(cullCallback);updateCallback = new SilverLiningUpdateCallback();updateCallback->camera = _view->getCamera();setUpdateCallback(updateCallback);computeBoundingBoxCallback = new SilverLiningSkyComputeBoundingBoxCallback();computeBoundingBoxCallback->camera = _view->getCamera();setComputeBoundingBoxCallback(computeBoundingBoxCallback);
}void SkyDrawable::setLighting(SilverLining::Atmosphere *atmosphere) const
{osg::Light *light = _view->getLight();osg::Vec4 ambient, diffuse;osg::Vec3 direction;if (atmosphere && light) {float ra, ga, ba, rd, gd, bd, x, y, z;atmosphere->GetAmbientColor(&ra, &ga, &ba);atmosphere->GetSunOrMoonColor(&rd, &gd, &bd);atmosphere->GetSunOrMoonPosition(&x, &y, &z);direction = osg::Vec3(x, y, z);ambient = osg::Vec4(ra, ga, ba, 1.0);diffuse = osg::Vec4(rd, gd, bd, 1.0);direction.normalize();light->setAmbient(ambient);light->setDiffuse(diffuse);light->setSpecular(osg::Vec4(0,0,0,1));light->setPosition(osg::Vec4(direction.x(), direction.y(), direction.z(), 0));}
}void SkyDrawable::initializeSilverLining(AtmosphereReference *ar) const
{if (ar && !ar->atmosphereInitialized) {ar->atmosphereInitialized = true; // only try once.SilverLining::Atmosphere *atmosphere = ar->atmosphere;if (atmosphere) {srand(1234); // constant random seed to ensure consistent clouds across windows// Update the path below to where you installed SilverLining's resources folder.const char *slPath = getenv("SILVERLINING_PATH");if (!slPath) {printf("Can't find SilverLining; set the SILVERLINING_PATH environment variable ");printf("to point to the directory containing the SDK.\n");exit(0);}std::string resPath(slPath);
#ifdef _WIN32resPath += "\\Resources\\";
#elseresPath += "/Resources/";
#endifint ret = atmosphere->Initialize(SilverLining::Atmosphere::OPENGL, resPath.c_str(),true, 0);if (ret != SilverLining::Atmosphere::E_NOERROR) {printf("SilverLining failed to initialize; error code %d.\n", ret);printf("Check that the path to the SilverLining installation directory is set properly ");printf("in SkyDrawable.cpp (in SkyDrawable::initializeSilverLining)\n");exit(0);}// Let SilverLining know which way is up. OSG usually has Z going up.atmosphere->SetUpVector(0, 0, 1);atmosphere->SetRightVector(1, 0, 0);// Set our location (change this to your own latitude and longitude)SilverLining::Location loc;loc.SetAltitude(0);loc.SetLatitude(45);loc.SetLongitude(-122);atmosphere->GetConditions()->SetLocation(loc);// Set the time to noon in PSTSilverLining::LocalTime t;t.SetFromSystemTime();t.SetHour(12);t.SetTimeZone(PST);atmosphere->GetConditions()->SetTime(t);// Center the clouds around the camera's initial positionosg::Vec3d pos = _view->getCameraManipulator()->getMatrix().getTrans();SilverLining::CloudLayer *cumulusCongestusLayer;cumulusCongestusLayer = SilverLining::CloudLayerFactory::Create(CUMULUS_CONGESTUS, *atmosphere);  //STRATUS //CUMULUS_CONGESTUS,CUMULUS_CONGESTUScumulusCongestusLayer->SetPrecipitation(SilverLining::CloudLayer::SLEET, 30.0);cumulusCongestusLayer->SetIsInfinite(true);cumulusCongestusLayer->SetBaseAltitude(4000);cumulusCongestusLayer->SetThickness(1500);//設置云層厚度cumulusCongestusLayer->SetBaseLength(80000); //40000cumulusCongestusLayer->SetBaseWidth(80000); //40000cumulusCongestusLayer->SetDensity(0.8);cumulusCongestusLayer->SetAlpha(0.8);cumulusCongestusLayer->SetWind(10.0f, 0.0f);  //設置風速和風向cumulusCongestusLayer->SetCloudAnimationEffects(1.0, true, 0, 0);//翻滾或卷動//cumulusCongestusLayer->SetPrecipitation(SilverLining::CloudLayer::DRY_SNOW, 20.0);cumulusCongestusLayer->SetFadeTowardEdges(true);//cumulusCongestusLayer->EnableFadeTowardGround(true);//cumulusCongestusLayer->EnablePrecipitationShadowing(true);          // 讓雨水與環境互動//cumulusCongestusLayer->EnableFadeTowardGround(true);// Note, we pass in X and -Y since this accepts "east" and "south" coordinates.cumulusCongestusLayer->SetLayerPosition(pos.x(), -pos.y());cumulusCongestusLayer->SeedClouds(*atmosphere);atmosphere->GetConditions()->AddCloudLayer(cumulusCongestusLayer);cullCallback->atmosphere = atmosphere;}}
}void SkyDrawable::drawImplementation(osg::RenderInfo& renderInfo) const
{SilverLining::Atmosphere *atmosphere = 0;AtmosphereReference *ar = dynamic_cast<AtmosphereReference *>(renderInfo.getCurrentCamera()->getUserData());if (ar) atmosphere = ar->atmosphere;renderInfo.getState()->disableAllVertexArrays();if (atmosphere) {initializeSilverLining(ar);osg::Matrix projMat = renderInfo.getState()->getProjectionMatrix();atmosphere->SetProjectionMatrix(projMat.ptr());osg::Matrix viewMat = renderInfo.getCurrentCamera()->getViewMatrix();atmosphere->SetCameraMatrix(viewMat.ptr());atmosphere->DrawSky(true, false, _skyboxSize, true, false);setLighting(atmosphere);}//if (atmosphere) {//	initializeSilverLining(ar);//	osg::Matrix projMat = renderInfo.getState()->getProjectionMatrix();//	atmosphere->SetProjectionMatrix(projMat.ptr());//	osg::Matrix viewMat = renderInfo.getCurrentCamera()->getViewMatrix();//	atmosphere->SetCameraMatrix(viewMat.ptr());//	atmosphere->DrawSky(true, false, _skyboxSize, true, false);//	setLighting(atmosphere);//	// 新增：渲染云層和降水//	//atmosphere->DrawObjects(true, true, true);//}//logCloudInfo(atmosphere);renderInfo.getState()->dirtyAllVertexArrays();
}void SkyDrawable::logCloudInfo(SilverLining::Atmosphere* atmosphere) const{if (!atmosphere) {std::cerr << "Atmosphere 是空指針！" << std::endl;return;}SilverLining::AtmosphericConditions* conditions = atmosphere->GetConditions();if (!conditions) {std::cerr << "無法獲取 AtmosphericConditions！" << std::endl;return;}// 自動推導類型，避免手動書寫 allocatorconst auto& layers = conditions->GetCloudLayers();std::cout << "云層數量：" << layers.size() << std::endl;for (const auto& entry : layers) {int id = entry.first;const SilverLining::CloudLayer* layer = entry.second;if (layer) {std::cout << "云層 ID " << id<< "：高度=" << layer->GetBaseAltitude()<< " 厚度=" << layer->GetThickness()<< " 密度=" << layer->GetDensity()<< " 透明度=" << layer->GetAlpha()<< std::endl;}}
}void SilverLiningUpdateCallback::update(osg::NodeVisitor*, osg::Drawable* drawable)
{SilverLining::Atmosphere *atmosphere = 0;AtmosphereReference *ar = dynamic_cast<AtmosphereReference *>(camera->getUserData());if (ar) {if (!ar->atmosphereInitialized) return;atmosphere = ar->atmosphere;}//if (atmosphere) {//    atmosphere->UpdateSkyAndClouds();//}// Since the skybox bounds are a function of the camera position, always update the bounds.drawable->dirtyBound();
}osg::BoundingBox SilverLiningSkyComputeBoundingBoxCallback::computeBound(const osg::Drawable& drawable) const
{osg::BoundingBox box;if (camera) {const SkyDrawable& skyDrawable = dynamic_cast<const SkyDrawable&>(drawable);SilverLining::Atmosphere *atmosphere = 0;AtmosphereReference *ar = dynamic_cast<AtmosphereReference *>(camera->getUserData());if (ar) {atmosphere = ar->atmosphere;}if (atmosphere) {double skyboxSize;if (skyDrawable.getSkyboxSize() != 0.0) {skyboxSize = skyDrawable.getSkyboxSize();} else {skyboxSize = atmosphere->GetConfigOptionDouble("sky-box-size");if (skyboxSize == 0.0) skyboxSize = 1000.0;}double radius = skyboxSize * 0.5;osg::Vec3f eye, center, up;camera->getViewMatrixAsLookAt(eye, center, up);osg::Vec3d camPos = eye;osg::Vec3d min(camPos.x() - radius, camPos.y() - radius, camPos.z() - radius);osg::Vec3d max(camPos.x() + radius, camPos.y() + radius, camPos.z() + radius);box.set(min, max);double dToOrigin = camPos.length();bool hasLimb = atmosphere->GetConfigOptionBoolean("enable-atmosphere-from-space");if (hasLimb) {// Compute bounds of atmospheric limb centered at 0,0,0double earthRadius = atmosphere->GetConfigOptionDouble("earth-radius-meters");double atmosphereHeight = earthRadius ++ atmosphere->GetConfigOptionDouble("atmosphere-height");double atmosphereThickness = atmosphere->GetConfigOptionDouble("atmosphere-scale-height-meters")+ earthRadius;osg::BoundingBox atmosphereBox;osg::Vec3d atmMin(-atmosphereThickness, -atmosphereThickness, -atmosphereThickness);osg::Vec3d atmMax(atmosphereThickness, atmosphereThickness, atmosphereThickness);// Expand these bounds by itbox.expandBy(atmosphereBox);}}}return box;
}