Add support for anisotropic filtering of StelTexture

Author: 10110111

guide/app_config_ini.tex

@@ -846,7 +846,9 @@ \subsection{\big[video\big]}
 viewport\_effect & string & This is used when the spheric mirror display mode is activated. Values include \emph{none} and \emph{sphericMirrorDistorter}.\\%\midrule
 minimum\_fps     & int    & Sets the minimum number of frames per second to display at (hardware performance permitting)\\%\midrule
 maximum\_fps     & int    & Sets the maximum number of frames per second to display at. This is useful to reduce power consumption in laptops.\\%\midrule
-multisampling    & int    & Sets the number of samples to use for multisampling antialiasing. \emph{0} disables antialiasing, \emph{1} is no-op (single sample per pixel), higher values increase smoothness and degrade performance. Too high a value may result in excessive blurriness of the GUI. A good starting value to try is \emph{4}.\\\bottomrule
+multisampling    & int    & Sets the number of samples to use for multisampling antialiasing. \emph{0} disables antialiasing, \emph{1} is no-op (single sample per pixel), higher values increase smoothness and degrade performance. Too high a value may result in excessive blurriness of the GUI. A good starting value to try is \emph{4}.\\
+	anisotropic\_filtering & int & Improves quality of rendering of inclined textured surfaces like e.g. planetary surface near the limb. Modern (and even quite old, like from 2010) GPUs can handle high anisotropy with no noticeable performance drop, so it should be fine to set this value as high as 16. The default is 0, which disables anisotropic filtering.\\
+\bottomrule
 \end{tabularx}
 
 \subsection{\big[viewing\big]}

src/StelMainView.cpp

@@ -77,6 +77,10 @@ Q_LOGGING_CATEGORY(mainview, "stel.MainView")
 
 #include <clocale>
 
+#ifndef GL_MAX_TEXTURE_MAX_ANISOTROPY
+# define GL_MAX_TEXTURE_MAX_ANISOTROPY 0x84FF
+#endif
+
 // Initialize static variables
 StelMainView* StelMainView::singleton = Q_NULLPTR;
 
@@ -864,6 +868,32 @@ void StelMainView::init()
 	glInfo.isGLES = format.renderableType()==QSurfaceFormat::OpenGLES;
 	qDebug().nospace() << "Luminance textures are " << (glInfo.supportsLuminanceTextures ? "" : "not ") << "supported";
 	glInfo.isCoreProfile = format.profile() == QSurfaceFormat::CoreProfile;
+	if(format.majorVersion() * 1000 + format.minorVersion() >= 4006 ||
+	   glInfo.mainContext->hasExtension("GL_EXT_texture_filter_anisotropic") ||
+	   glInfo.mainContext->hasExtension("GL_ARB_texture_filter_anisotropic"))
+	{
+		StelOpenGL::clearGLErrors();
+		auto& gl = *QOpenGLContext::currentContext()->functions();
+		gl.glGetIntegerv(GL_MAX_TEXTURE_MAX_ANISOTROPY, &glInfo.maxAnisotropy);
+		const auto error = gl.glGetError();
+		if(error != GL_NO_ERROR)
+		{
+			qDebug() << "Failed to get maximum texture anisotropy:" << StelOpenGL::getGLErrorText(error);
+		}
+		else if(glInfo.maxAnisotropy > 0)
+		{
+			qDebug() << "Maximum texture anisotropy:" << glInfo.maxAnisotropy;
+		}
+		else
+		{
+			qDebug() << "Maximum texture anisotropy is not positive:" << glInfo.maxAnisotropy;
+			glInfo.maxAnisotropy = 0;
+		}
+	}
+	else
+	{
+		qDebug() << "Anisotropic filtering is not supported!";
+	}
 
 	gui = new StelGui();
 

src/StelMainView.hpp

@@ -72,6 +72,7 @@ class StelMainView : public QGraphicsView
 		QSurface* surface;
 		QOpenGLContext* mainContext;
 		QOpenGLFunctions* functions;
+		GLint maxAnisotropy = 0;
 		bool supportsLuminanceTextures = false;
 		bool isCoreProfile = false;
 		bool isGLES = false;

src/core/StelTexture.cpp

@@ -35,6 +35,10 @@
 #include <QFuture>
 #include <QtConcurrent>
 
+#ifndef GL_TEXTURE_MAX_ANISOTROPY
+# define GL_TEXTURE_MAX_ANISOTROPY 0x84FE
+#endif
+
 StelTexture::StelTexture(StelTextureMgr *mgr) : textureMgr(mgr), gl(Q_NULLPTR), networkReply(Q_NULLPTR), loader(Q_NULLPTR), errorOccured(false), alphaChannel(false), id(0),
 	width(-1), height(-1), glSize(0)
 {
@@ -411,8 +415,26 @@ bool StelTexture::glLoad(const GLData& data)
 	if (loadParams.generateMipmaps)
 	{
 		gl->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, loadParams.filterMipmaps ? GL_LINEAR_MIPMAP_LINEAR : GL_LINEAR_MIPMAP_NEAREST);
+
+		const auto conf = StelApp::getInstance().getSettings();
+		const GLint desiredAnisotropyLevel = conf->value("video/anisotropic_filtering", 0).toUInt();
+		const auto maxAnisotropy = StelMainView::getInstance().getGLInformation().maxAnisotropy;
+		if(maxAnisotropy > 0 && desiredAnisotropyLevel > 0)
+		{
+			const int anisotropy = std::min(maxAnisotropy, desiredAnisotropyLevel);
+			gl->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY, anisotropy);
+
+			// Assuming maximum possible anisotropy, all mipmaps will require
+			// 4× the size of base mip level. Generally anisotropy may be
+			// lower, but we prefer to overestimate VRAM consumption than to
+			// underestimate it.
+			glSize *= 4;
+		}
+		else
+		{
+			glSize = glSize + glSize/3; //mipmaps require 1/3 more mem
+		}
 		gl->glGenerateMipmap(GL_TEXTURE_2D);
-		glSize = glSize + glSize/3; //mipmaps require 1/3 more mem
 	}
 
 	//register ID with textureMgr and increment size