Prefer immutable texture storage when available

irr/include/irrMath.h

@@ -283,6 +283,17 @@ inline s32 s32_clamp(s32 value, s32 low, s32 high)
 	return clamp(value, low, high);
 }
 
+// integer log2 of an integer. returning 0 if denormal
+inline s32 u32_log2(u32 in)
+{
+	s32 ret = 0;
+	while (in > 1) {
+		in >>= 1;
+		ret++;
+	}
+	return ret;
+}
+
 /*
 	float IEEE-754 bit representation
 

irr/src/CImage.cpp

@@ -363,7 +363,7 @@ inline SColor CImage::getPixelBox(s32 x, s32 y, s32 fx, s32 fy, s32 bias) const
 		}
 	}
 
-	s32 sdiv = s32_log2_s32(fx * fy);
+	s32 sdiv = core::u32_log2(fx * fy);
 
 	a = core::s32_clamp((a >> sdiv) + bias, 0, 255);
 	r = core::s32_clamp((r >> sdiv) + bias, 0, 255);

irr/src/COpenGLCoreFeature.h

@@ -14,20 +14,18 @@ namespace video
 class COpenGLCoreFeature
 {
 public:
-	COpenGLCoreFeature() :
+	COpenGLCoreFeature() = default;
-			BlendOperation(false), ColorAttachment(0), MultipleRenderTarget(0), MaxTextureUnits(1)
-	{
-	}
 
 	virtual ~COpenGLCoreFeature()
 	{
 	}
 
-	bool BlendOperation;
+	bool BlendOperation = false;
+	bool TexStorage = false;
 
-	u8 ColorAttachment;
+	u8 ColorAttachment = 0;
-	u8 MultipleRenderTarget;
+	u8 MultipleRenderTarget = 0;
-	u8 MaxTextureUnits;
+	u8 MaxTextureUnits = 0;
 };
 
 }

irr/src/COpenGLCoreTexture.h

@@ -503,10 +503,22 @@ protected:
 			return;
 		}
 
+		u32 levels = 1;
+		if (HasMipMaps) {
+			levels = core::u32_log2(core::max_(Size.Width, Size.Height)) + 1;
+		}
+
+		// reference: <https://www.khronos.org/opengl/wiki/Texture_Storage>
+
 		switch (Type) {
 		case ETT_2D:
-			GL.TexImage2D(TextureType, 0, InternalFormat,
+			if (Driver->getFeature().TexStorage) {
-				Size.Width, Size.Height, 0, PixelFormat, PixelType, 0);
+				GL.TexStorage2D(TextureType, levels, InternalFormat,
+					Size.Width, Size.Height);
+			} else {
+				GL.TexImage2D(TextureType, 0, InternalFormat,
+					Size.Width, Size.Height, 0, PixelFormat, PixelType, 0);
+			}
 			TEST_GL_ERROR(Driver);
 			break;
 		case ETT_2D_MS: {
@@ -531,8 +543,14 @@ protected:
 		}
 		case ETT_CUBEMAP:
 			for (u32 i = 0; i < 6; i++) {
-				GL.TexImage2D(getTextureTarget(i), 0, InternalFormat,
+				GLenum target = getTextureTarget(i);
-					Size.Width, Size.Height, 0, PixelFormat, PixelType, 0);
+				if (Driver->getFeature().TexStorage) {
+					GL.TexStorage2D(target, levels, InternalFormat,
+						Size.Width, Size.Height);
+				} else {
+					GL.TexImage2D(target, 0, InternalFormat,
+						Size.Width, Size.Height, 0, PixelFormat, PixelType, 0);
+				}
 				TEST_GL_ERROR(Driver);
 			}
 			break;

irr/src/OpenGL3/Driver.cpp

@@ -78,6 +78,7 @@ void COpenGL3Driver::initFeatures()
 	// COGLESCoreExtensionHandler::Feature
 	static_assert(MATERIAL_MAX_TEXTURES <= 16, "Only up to 16 textures are guaranteed");
 	Feature.BlendOperation = true;
+	Feature.TexStorage = isVersionAtLeast(4, 2) || queryExtension("GL_ARB_texture_storage");
 	Feature.ColorAttachment = GetInteger(GL_MAX_COLOR_ATTACHMENTS);
 	Feature.MaxTextureUnits = MATERIAL_MAX_TEXTURES;
 	Feature.MultipleRenderTarget = GetInteger(GL_MAX_DRAW_BUFFERS);

irr/src/OpenGLES2/Driver.cpp

@@ -131,6 +131,7 @@ void COpenGLES2Driver::initFeatures()
 	// COGLESCoreExtensionHandler::Feature
 	static_assert(MATERIAL_MAX_TEXTURES <= 8, "Only up to 8 textures are guaranteed");
 	Feature.BlendOperation = true;
+	Feature.TexStorage = Version.Major >= 3 || queryExtension("GL_ARB_texture_storage");
 	Feature.ColorAttachment = 1;
 	if (MRTSupported)
 		Feature.ColorAttachment = GetInteger(GL_MAX_COLOR_ATTACHMENTS);

irr/src/SoftwareDriver2_helper.h

@@ -93,17 +93,6 @@ inline void memset16(void *dest, const u16 value, size_t bytesize)
 	}
 }
 
-// integer log2 of an integer. returning 0 as denormal
-static inline s32 s32_log2_s32(u32 in)
-{
-	s32 ret = 0;
-	while (in > 1) {
-		in >>= 1;
-		ret++;
-	}
-	return ret;
-}
-
 // ------------------ Video---------------------------------------
 /*!
 	Pixel = dest * ( 1 - alpha ) + source * alpha