网站排名易下拉用法,网站建设价格差异好大,wordpress 标签云插件下载,站长网站查询又到了开心的公式时刻了。 先看看渲染方程 现在关注第二部分#xff0c;镜面反射。 其中 这里很棘手#xff0c;与输入wi和输出w0都有关系#xff0c;所以#xff0c;再近似 其中第一部分#xff0c;就是预滤波环境贴图#xff0c;形式上与前面的辐照度图很相似#…又到了开心的公式时刻了。 先看看渲染方程 现在关注第二部分镜面反射。 其中 这里很棘手与输入wi和输出w0都有关系所以再近似 其中第一部分就是预滤波环境贴图形式上与前面的辐照度图很相似那么能不能用同样的方法呢 先看看镜面反射和漫反射的图 可以看到镜面反射是绕着出射向量的一个范围成为波瓣而漫反射是绕着法线方向均匀分布的。 再想想积分辐照度图时是以法线向量为中心进行积分的。 那很自然的想到积分镜面反射的预滤波环境贴图可以以出射向量为中心在波瓣范围内积分。
然而 波瓣有大有小是因为粗糙度不同 所以不能只积分一次而是多次按照不同粗糙度积分后写到mipmap或者单独的纹理中。这里为了方便分别写到不同的纹理中。
那么该如何积分呢辐照度图是在经度0到360纬度0到90内均匀积分。
而镜面反射中给定入射方向波瓣指向方向就是微平面半向量的反射方向。所以只在波瓣内积分就可以了即重要性采样。 这时就可以使用蒙特卡洛积分即在大数定律基础上采取N样本即可。N越大越准。pdf为概率密度函数。 比如 采样样本越多越靠近中间范围。因为中间范围概率大。
以上为均匀采样
如果采样样本有偏则会更快收敛。比如通过低差异序列获取样本。 float RadicalInverse_VdC(uint bits) { bits (bits 16u) | (bits 16u); bits ((bits 0x55555555u) 1u) | ((bits 0xAAAAAAAAu) 1u); bits ((bits 0x33333333u) 2u) | ((bits 0xCCCCCCCCu) 2u); bits ((bits 0x0F0F0F0Fu) 4u) | ((bits 0xF0F0F0F0u) 4u); bits ((bits 0x00FF00FFu) 8u) | ((bits 0xFF00FF00u) 8u); return float(bits) * 2.3283064365386963e-10; // / 0x100000000 }
vec2 Hammersley(uint i, uint N) { return vec2(float(i)/float(N), RadicalInverse_VdC(i)); } 或者无位运算的 float VanDerCorpus(uint n, uint base) { float invBase 1.0 / float(base); float denom 1.0; float result 0.0; for (uint i 0u; i 32u; i) { if (n 0u) { denom mod(float(n), 2.0); result denom * invBase; invBase invBase / 2.0; n uint(float(n) / 2.0); } } return result; } vec2 HammersleyNoBitOps(uint i, uint N) { return vec2(float(i) / float(N), VanDerCorpus(i, 2u)); }
然后根据法线方向粗糙度和低差异序列生成采样向量该向量大体围绕着预估的波瓣方向。 “vec3 ImportanceSampleGGX(vec2 Xi, vec3 N, float roughness)” “{” “float a roughness * roughness;” “float phi 2.0 * PI * Xi.x;” “float cosTheta sqrt((1.0 - Xi.y)/(1.0(a*a-1.0) * Xi.y));” “float sinTheta sqrt(1.0 - cosTheta * cosTheta);” “vec3 H;” “H.x cos(phi) * sinTheta;” “H.y sin(phi) * sinTheta;” “H.z cosTheta;” “vec3 up abs(N.z) 0.999 ? vec3(0.0,0.0,1.0) : vec3(1.0,0.0,0.0);” “vec3 tangent normalize(cross(up,N));” “vec3 bitangent cross(N,tangent);” “vec3 sampleVec tangent * H.x bitangent * H.y N * H.z;” “return normalize(sampleVec);” “}” 运行结果如下 代码如下 #include osg/TextureCubeMap #include osg/TexGen #include osg/TexEnvCombine #include osgUtil/ReflectionMapGenerator #include osgDB/ReadFile #include osgViewer/Viewer #include osg/NodeVisitor #include osg/ShapeDrawable
static const char * vertexShader { //“#version 120 core\n” “in vec3 aPos;\n” “varying vec3 localPos;\n” “void main(void)\n” “{\n” “localPos aPos;\n” gl_Position ftransform();\n //“gl_Position view * view * vec4(aPos,1.0);” “}\n” };
static const char psShader { “varying vec3 localPos;\n” “uniform samplerCube environmentMap;” “uniform float roughness;” “const float PI 3.1415926;” “float VanDerCorpus(uint n, uint base) “{ float invBase 1.0 / float(base); float denom 1.0; float result 0.0; for (uint i 0u; i 32u; i) { if (n 0u) { denom mod(float(n), 2.0); result denom * invBase; invBase invBase / 2.0; n uint(float(n) / 2.0); } } “return result; “} “vec2 HammersleyNoBitOps(uint i, uint N) “{ return vec2(float(i) / float(N), VanDerCorpus(i, 2u)); “} //“float RadicalInverse_Vdc(uint bits)\n” //”{” //“bits (bits 16u) | (bits 16u);” //“bits ((bits 0x55555555u) 1u ) | (bits 0xAAAAAAAAu) 1u);” //“bits ((bits 0x33333333u) 2u ) | (bits 0xCCCCCCCCu) 2u);” //“bits ((bits 0x0F0F0F0Fu) 4u ) | (bits 0xF0F0F0F0u) 4u);” //“bits ((bits 0x00FF00FFu) 8u ) | (bits 0xFF00FF00u) 8u);” //“return float(bits) * 2.3283064365386963e-10;” //”}” //“vec2 Hammersley(uint i, uint N)” //”{” //“return vec2(float(i) / float(N), RadicalInverse_Vdc(i));” //”} “vec3 ImportanceSampleGGX(vec2 Xi, vec3 N, float roughness)” “{” “float a roughness * roughness;” “float phi 2.0 * PI * Xi.x;” float cosTheta sqrt((1.0 - Xi.y)/(1.0(aa-1.0) * Xi.y)); “float sinTheta sqrt(1.0 - cosTheta * cosTheta);” “vec3 H;” “H.x cos(phi) * sinTheta;” “H.y sin(phi) * sinTheta;” “H.z cosTheta;” “vec3 up abs(N.z) 0.999 ? vec3(0.0,0.0,1.0) : vec3(1.0,0.0,0.0);” “vec3 tangent normalize(cross(up,N));” “vec3 bitangent cross(N,tangent);” “vec3 sampleVec tangent * H.x bitangent * H.y N * H.z;” “return normalize(sampleVec);” “}” void main() { vec3 N normalize(localPos); vec3 R N; vec3 V R; const uint SAMPLE_COUNT 1024u; float totalWeight 0.0; vec3 prefilteredColor vec3(0.0); for (uint i 0u; i SAMPLE_COUNT; i) { vec2 Xi HammersleyNoBitOps(i, SAMPLE_COUNT); vec3 H ImportanceSampleGGX(Xi, N, roughness); vec3 L normalize(2.0 * dot(V, H) * H - V); float NdotL max(dot(N, L), 0.0); if (NdotL 0.0) { prefilteredColor texture(environmentMap, L).rgb * NdotL; totalWeight NdotL; } } prefilteredColor prefilteredColor / totalWeight; gl_FragColor vec4(prefilteredColor, 1.0); } }; class MyNodeVisitor : public osg::NodeVisitor { public: MyNodeVisitor() : osg::NodeVisitor(osg::NodeVisitor::TRAVERSE_ALL_CHILDREN) {
}
void apply(osg::Geode geode)
{int count geode.getNumDrawables();for (int i 0; i count; i){osg::ref_ptrosg::Geometry geometry geode.getDrawable(i)-asGeometry();if (!geometry.valid()){continue;}osg::Array* vertexArray geometry-getVertexArray();geometry-setVertexAttribArray(1, vertexArray);}traverse(geode);
}};
int main() {
osg::ref_ptrosgViewer::Viewer viewer new osgViewer::Viewer;osg::ref_ptrosg::TextureCubeMap tcm new osg::TextureCubeMap;
tcm-setTextureSize(128, 128);
tcm-setFilter(osg::Texture::MIN_FILTER, osg::Texture::LINEAR_MIPMAP_LINEAR);
tcm-setFilter(osg::Texture::MAG_FILTER, osg::Texture::LINEAR);
tcm-setWrap(osg::Texture::WRAP_S, osg::Texture::CLAMP_TO_EDGE);
tcm-setWrap(osg::Texture::WRAP_T, osg::Texture::CLAMP_TO_EDGE);
tcm-setWrap(osg::Texture::WRAP_R, osg::Texture::CLAMP_TO_EDGE);std::string strImagePosX D:/hdr/Right face camera.bmp;
osg::ref_ptrosg::Image imagePosX osgDB::readImageFile(strImagePosX);
tcm-setImage(osg::TextureCubeMap::POSITIVE_X, imagePosX);
std::string strImageNegX D:/hdr/Left face camera.bmp;
osg::ref_ptrosg::Image imageNegX osgDB::readImageFile(strImageNegX);
tcm-setImage(osg::TextureCubeMap::NEGATIVE_X, imageNegX);std::string strImagePosY D:/hdr/Front face camera.bmp;;
osg::ref_ptrosg::Image imagePosY osgDB::readImageFile(strImagePosY);
tcm-setImage(osg::TextureCubeMap::POSITIVE_Y, imagePosY);
std::string strImageNegY D:/hdr/Back face camera.bmp;;
osg::ref_ptrosg::Image imageNegY osgDB::readImageFile(strImageNegY);
tcm-setImage(osg::TextureCubeMap::NEGATIVE_Y, imageNegY);std::string strImagePosZ D:/hdr/Top face camera.bmp;
osg::ref_ptrosg::Image imagePosZ osgDB::readImageFile(strImagePosZ);
tcm-setImage(osg::TextureCubeMap::POSITIVE_Z, imagePosZ);std::string strImageNegZ D:/hdr/Bottom face camera.bmp;
osg::ref_ptrosg::Image imageNegZ osgDB::readImageFile(strImageNegZ);
tcm-setImage(osg::TextureCubeMap::NEGATIVE_Z, imageNegZ);
tcm-setUseHardwareMipMapGeneration(true);
float minMipMapLevel 0.0;
float maxMipMapLevel 4.0;
tcm-setMinLOD(minMipMapLevel);
tcm-setMaxLOD(maxMipMapLevel);osg::ref_ptrosg::Box box new osg::Box(osg::Vec3(0, 0, 0), 10);
osg::ref_ptrosg::ShapeDrawable drawable new osg::ShapeDrawable(box);
osg::ref_ptrosg::Geode geode new osg::Geode;
geode-addDrawable(drawable);
MyNodeVisitor nv;
geode-accept(nv);
osg::ref_ptrosg::StateSet stateset geode-getOrCreateStateSet();
stateset-setTextureAttributeAndModes(0, tcm, osg::StateAttribute::OVERRIDE | osg::StateAttribute::ON);//shaderosg::ref_ptrosg::Shader vs1 new osg::Shader(osg::Shader::VERTEX, vertexShader);
osg::ref_ptrosg::Shader ps1 new osg::Shader(osg::Shader::FRAGMENT, psShader);
osg::ref_ptrosg::Program program1 new osg::Program;
program1-addShader(vs1);
program1-addShader(ps1);
program1-addBindAttribLocation(aPos, 1);osg::ref_ptrosg::Uniform environmentMapUniform new osg::Uniform(environmentMap, 0);
stateset-addUniform(environmentMapUniform);
float theMip 3.0;
float roughness theMip / maxMipMapLevel;
osg::ref_ptrosg::Uniform roughnessUniform new osg::Uniform(roughness, roughness);
stateset-addUniform(roughnessUniform);stateset-setAttribute(program1, osg::StateAttribute::ON);viewer-setSceneData(geode);
viewer-realize();
return viewer-run();}
