From: Mikko Rasa <tdb@tdb.fi>
Date: Wed, 17 Nov 2021 13:39:01 +0000 (+0200)
Subject: Add support for padding in vertex formats
X-Git-Url: http://git.tdb.fi/?a=commitdiff_plain;h=8a8cce8ef4ee28b3572a72958b8b407759f9f826;p=libs%2Fgl.git

Add support for padding in vertex formats

Vulkan requires attributes to be correctly aligned, so depending on the
combination of types padding may be necessary.  It's better to make it
explicit so support for raw mesh data files can be added in the future.
---

diff --git a/source/backends/opengl/vertexsetup_backend.cpp b/source/backends/opengl/vertexsetup_backend.cpp
index acd14f48..d45481f9 100644
--- a/source/backends/opengl/vertexsetup_backend.cpp
+++ b/source/backends/opengl/vertexsetup_backend.cpp
@@ -87,27 +87,30 @@ void OpenGLVertexSetup::update_vertex_array(const VertexArray &array, unsigned b
 	for(VertexAttribute a: fmt)
 	{
 		unsigned sem = get_attribute_semantic(a);
-		bool integer = is_integer_attribute(a);
-		GLenum type = get_gl_type(get_attribute_source_type(a));
-		unsigned cc = get_attribute_component_count(a);
-		if(direct)
-		{
-			if(integer)
-				glVertexArrayAttribIFormat(id, sem, cc, type, offset);
-			else
-				glVertexArrayAttribFormat(id, sem, cc, type, true, offset);
-			glVertexArrayAttribBinding(id, sem, binding);
-			glEnableVertexArrayAttrib(id, sem);
-		}
-		else
+		if(!is_padding(a))
 		{
-			if(integer)
-				glVertexAttribIPointer(sem, cc, type, stride, reinterpret_cast<void *>(offset));
+			bool integer = is_integer_attribute(a);
+			GLenum type = get_gl_type(get_attribute_source_type(a));
+			unsigned cc = get_attribute_component_count(a);
+			if(direct)
+			{
+				if(integer)
+					glVertexArrayAttribIFormat(id, sem, cc, type, offset);
+				else
+					glVertexArrayAttribFormat(id, sem, cc, type, true, offset);
+				glVertexArrayAttribBinding(id, sem, binding);
+				glEnableVertexArrayAttrib(id, sem);
+			}
 			else
-				glVertexAttribPointer(sem, cc, type, true, stride, reinterpret_cast<void *>(offset));
-			if(ARB_instanced_arrays)
-				glVertexAttribDivisor(sem, divisor);
-			glEnableVertexAttribArray(sem);
+			{
+				if(integer)
+					glVertexAttribIPointer(sem, cc, type, stride, reinterpret_cast<void *>(offset));
+				else
+					glVertexAttribPointer(sem, cc, type, true, stride, reinterpret_cast<void *>(offset));
+				if(ARB_instanced_arrays)
+					glVertexAttribDivisor(sem, divisor);
+				glEnableVertexAttribArray(sem);
+			}
 		}
 		offset += get_attribute_size(a);
 	}
@@ -130,17 +133,19 @@ void OpenGLVertexSetup::unload()
 		glBindBuffer(GL_ARRAY_BUFFER, 0);
 
 		for(VertexAttribute a: static_cast<const VertexSetup *>(this)->vertex_format)
-		{
-			unsigned sem = get_attribute_semantic(a);
-			glDisableVertexAttribArray(sem);
-			glVertexAttribPointer(sem, 1, GL_FLOAT, false, 0, 0);
-		}
+			if(!is_padding(a))
+			{
+				unsigned sem = get_attribute_semantic(a);
+				glDisableVertexAttribArray(sem);
+				glVertexAttribPointer(sem, 1, GL_FLOAT, false, 0, 0);
+			}
 		for(VertexAttribute a: static_cast<const VertexSetup *>(this)->inst_format)
-		{
-			unsigned sem = get_attribute_semantic(a);
-			glDisableVertexAttribArray(sem);
-			glVertexAttribPointer(sem, 1, GL_FLOAT, false, 0, 0);
-		}
+			if(!is_padding(a))
+			{
+				unsigned sem = get_attribute_semantic(a);
+				glDisableVertexAttribArray(sem);
+				glVertexAttribPointer(sem, 1, GL_FLOAT, false, 0, 0);
+			}
 
 		glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
 	}
diff --git a/source/builders/vertexarraybuilder.cpp b/source/builders/vertexarraybuilder.cpp
index c9a1f3bc..00ff0012 100644
--- a/source/builders/vertexarraybuilder.cpp
+++ b/source/builders/vertexarraybuilder.cpp
@@ -16,12 +16,12 @@ void VertexArrayBuilder::vertex_(const Vector4 &vtx)
 	for(VertexAttribute a: array.get_format())
 	{
 		unsigned sem = get_attribute_semantic(a);
-		bool integer = is_integer_attribute(a);
-		DataType type = get_attribute_source_type(a);
-		unsigned cc = get_attribute_component_count(a);
-
-		if(sem<attr.size())
+		if(!is_padding(a) && sem<attr.size())
 		{
+			bool integer = is_integer_attribute(a);
+			DataType type = get_attribute_source_type(a);
+			unsigned cc = get_attribute_component_count(a);
+
 			const Vector4 &value = (sem==0 ? vtx : attr[sem]);
 			if(type==UNSIGNED_BYTE)
 				store_attribute<uint8_t>(ptr, value, !integer, cc);
diff --git a/source/core/vertexformat.cpp b/source/core/vertexformat.cpp
index ff043f7d..3db7542f 100644
--- a/source/core/vertexformat.cpp
+++ b/source/core/vertexformat.cpp
@@ -188,7 +188,8 @@ void operator>>(const LexicalConverter &conv, VertexAttribute &a)
 			convert_attribute(str, "GROUP", 1, 4, a, GROUP1) ||
 			convert_attribute(str, "WEIGHT", 1, 4, a, WEIGHT1) ||
 			convert_attribute(str, "TEXCOORD", 1, 4, a, TEXCOORD1) ||
-			convert_attribute(str, "GENERIC", 1, 4, a, GENERIC1))
+			convert_attribute(str, "GENERIC", 1, 4, a, GENERIC1) ||
+			convert_attribute(str, "PADDING", 1, 4, a, PADDING1))
 			return;
 	}
 	catch(...)
diff --git a/source/core/vertexformat.h b/source/core/vertexformat.h
index 64c89e13..fba206e4 100644
--- a/source/core/vertexformat.h
+++ b/source/core/vertexformat.h
@@ -61,6 +61,10 @@ enum VertexAttribute: std::uint16_t
 	GENERIC_I2 = 0x28CA,
 	GENERIC_I3 = 0x28CB,
 	GENERIC_I4 = 0x28CC,
+	PADDING1 = 0xF811,
+	PADDING2 = 0xF812,
+	PADDING3 = 0xF813,
+	PADDING4 = 0xF814,
 	RAW_ATTRIB1 = 0xFDC1,
 	RAW_ATTRIB2 = 0xFDC2,
 	RAW_ATTRIB3 = 0xFDC3,
@@ -134,6 +138,9 @@ inline unsigned get_attribute_size(VertexAttribute a)
 inline bool is_integer_attribute(VertexAttribute a)
 { return a&8; }
 
+inline bool is_padding(VertexAttribute a)
+{ return get_attribute_semantic(a)==get_attribute_semantic(PADDING1); }
+
 void operator>>(const LexicalConverter &, VertexAttribute &);
 
 } // namespace GL
diff --git a/source/core/vertexsetup.cpp b/source/core/vertexsetup.cpp
index 61bf032c..2994916e 100644
--- a/source/core/vertexsetup.cpp
+++ b/source/core/vertexsetup.cpp
@@ -73,7 +73,7 @@ bool VertexSetup::verify_format(const VertexFormat &fmt)
 		return false;
 
 	static unsigned max_attribs = Device::get_current().get_info().limits.max_vertex_attributes;
-	return all_of(fmt.begin(), fmt.end(), [](VertexAttribute a){ return get_attribute_semantic(a)<max_attribs; });
+	return all_of(fmt.begin(), fmt.end(), [](VertexAttribute a){ return is_padding(a) || get_attribute_semantic(a)<max_attribs; });
 }
 
 void VertexSetup::update() const