upstream from ditt : fix normalmap format delivery issue

normalmaps are usually encoded in [0,255] UNORM then decoded via 2x-1 therefore there's no way to express a 0.0, meaning 127 got interpreted as (0.003,-0.003,1.0), added an epsilon to produce 0 len normals.

Author: devshgraphicsprogramming

include/nbl/asset/filters/CCopyImageFilter.h

@@ -49,7 +49,6 @@ class CCopyImageFilter : public CImageFilter<CCopyImageFilter>, public CMatchedS
 				return false;
 
 			return getFormatClass(state->inImage->getCreationParameters().format)==getFormatClass(state->outImage->getCreationParameters().format);
-			return true;
 		}
 
 		template<class ExecutionPolicy>

include/nbl/asset/filters/CNormalMapToDerivativeFilter.h

@@ -22,17 +22,22 @@ namespace nbl::asset
 */
 struct NormalMapToDerivativeMapSwizzle
 {
+	// since most normalmaps are supplied in RG8_UNORM
+	double zeroEpsilon = 1.0/255.0;
+
 	template<typename InT, typename OutT>
 	void operator()(const InT* in, OutT* out) const
 	{
 		const auto* _in = reinterpret_cast<const std::conditional_t<std::is_void_v<InT>,uint64_t,InT>*>(in);
 		auto* _out = reinterpret_cast<std::conditional_t<std::is_void_v<OutT>,uint64_t,OutT>*>(out);
 		const auto xDecode = _in[0]*2.f-1.f;
 		const auto yDecode = _in[1]*2.f-1.f;
+		// TODO: a template parameter to decide if Z is in [0,1] or [-1,1]
 		const auto zDecode = _in[2]*2.f-1.f;
-		_out[0] = -xDecode/zDecode;
+		// because normalmaps are supplied in UNORM formats, there's no true zero
+		_out[0] = core::abs(xDecode)>zeroEpsilon ? (-xDecode/zDecode):0.f;
 		// scanlines go from top down, so Y component is in reverse
-		_out[1] = yDecode/zDecode;
+		_out[1] = core::abs(yDecode)>zeroEpsilon ? (yDecode/zDecode):0.f;
 	}
 };
 

include/nbl/asset/utils/CDerivativeMapCreator.h

@@ -1,5 +1,5 @@
-#ifndef __NBL_I_DERIVATIVE_MAP_CREATOR_H_INCLUDED__
-#define __NBL_I_DERIVATIVE_MAP_CREATOR_H_INCLUDED__
+#ifndef _NBL_I_DERIVATIVE_MAP_CREATOR_H_INCLUDED_
+#define _NBL_I_DERIVATIVE_MAP_CREATOR_H_INCLUDED_
 
 #include "nbl/asset/ICPUImage.h"
 #include "nbl/asset/ICPUImageView.h"