osgearth 实现简单的雷达扫描

一、前言

通过使用着色器，实现简单的贴地扫描效果，基于此效果可以添加线框、刻度盘等。

二、效果

非贴地

贴地

三、几何体构建

osg::ref_ptr<osg::Node> EntityRadarScan::BuildEntityBody() { Style circleStyle; //circleStyle.getOrCreate<PolygonSymbol>()->fill()->color() = Color(Color::Cyan, 0.5); circleStyle.getOrCreate<AltitudeSymbol>()->clamping() = AltitudeSymbol::CLAMP_TO_TERRAIN; circleStyle.getOrCreate<AltitudeSymbol>()->technique() = AltitudeSymbol::TECHNIQUE_DRAPE; circle = new CircleNode( DigitalEarthWidget::GetInstance()->m_pMapNode.get(), GeoPoint(DigitalEarthWidget::GetInstance()->m_pMapNode->getMapSRS(), m_stLocation.dLng, m_stLocation.dLat, m_stLocation.dAlt, ALTMODE_ABSOLUTE), Distance(m_iRadius, Units::METERS), circleStyle, Angle(0.0, Units::DEGREES), Angle(360.0, Units::DEGREES), true); CreateShaders(*(circle->getOrCreateStateSet())); return circle.get(); }

四、着色器代码

void EntityRadarScan::InitShaderProgram(QString &strVert, QString &strFrag)const { strVert = "\ varying vec2 v_texcoord;\ void main() {\ v_texcoord = gl_Vertex.xy;\ gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\ }"; strFrag = "\ uniform float simTime;\ uniform vec4 baseColor;\ uniform vec4 scanColor;\ varying vec2 v_texcoord;\ const float pi = 3.1415926;\n\ void main() {\ vec2 pos = normalize(v_texcoord);\n\ // 计算当前角度(0-2π)\n\ float angle = atan(pos.y, pos.x)+pi;\n\ // 将时间转换为旋转角度(0-2π)\n\ float scanAngle = mod(simTime , 2*pi);\n\ // 计算角度差值(0-2π)\n\ float angleDiff = mod(angle - scanAngle , 2*pi);\n\ if(angleDiff>1.0){\n\ gl_FragColor = baseColor;\n\ }else {\n\ gl_FragColor = mix(baseColor, scanColor, angleDiff<0.0?0.0:angleDiff); \n\ }\n\ }"; } void EntityRadarScan::CreateShaders(osg::StateSet& ss) { QString m_strVertSource; QString m_strfragSource; InitShaderProgram(m_strVertSource, m_strfragSource); osg::ref_ptr<osg::Shader> vertShader = new osg::Shader(osg::Shader::VERTEX, m_strVertSource.toStdString()); osg::ref_ptr<osg::Shader> fragShader = new osg::Shader(osg::Shader::FRAGMENT, m_strfragSource.toStdString()); osg::ref_ptr<osg::Program> program = new osg::Program; program->addShader(vertShader.get()); program->addShader(fragShader.get()); osg::ref_ptr<osg::Uniform> simTime = new osg::Uniform("simTime", 1.0f); ss.addUniform(simTime.get()); osg::ref_ptr<osg::Uniform> baseColor = new osg::Uniform("baseColor", m_baseColor); ss.addUniform(baseColor.get()); osg::ref_ptr<osg::Uniform> scanColor = new osg::Uniform("scanColor", m_scanColor); ss.addUniform(scanColor.get()); ss.setAttributeAndModes(program.get()); ss.setAttributeAndModes(program.get(), osg::StateAttribute::OVERRIDE | osg::StateAttribute::ON); ss.setMode(GL_BLEND, osg::StateAttribute::ON); ss.setAttributeAndModes(new osg::BlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)); ss.setRenderingHint(osg::StateSet::TRANSPARENT_BIN); //ss.setRenderBinDetails(99, "RenderBin"); // 使用更高的渲染顺序 }

五、传值驱动

bool EntityRadarScan::EntityUpdate(osg::Node* node, osg::NodeVisitor* nv) { setMatrix(GetLocationMatrix()); if (circle) { osg::StateSet* stateset = circle->getOrCreateStateSet(); osg::Uniform* simTime = stateset->getUniform("simTime"); if (simTime) { float alpha = (float)(osg::Timer::instance()->time_s())*2.0; //OSG_WARN << alpha << std::endl; simTime->set(alpha); } } return true; }

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