From: Mikko Rasa <tdb@tdb.fi>
Date: Fri, 21 Jun 2019 08:32:46 +0000 (+0300)
Subject: Obtain the instance transform location from shader program
X-Git-Url: http://git.tdb.fi/?p=libs%2Fgl.git;a=commitdiff_plain;h=c041ea998569f24b2af9c5af47dffd337ff78146

Obtain the instance transform location from shader program
---

diff --git a/source/instancearray.cpp b/source/instancearray.cpp
index 4156c6f3..29b59f09 100644
--- a/source/instancearray.cpp
+++ b/source/instancearray.cpp
@@ -24,13 +24,29 @@ InstanceArray::InstanceArray(const Object &o):
 	instance_data(0),
 	instance_buffer(0),
 	vtx_setup(0),
+	matrix_location(-1),
 	matrix_offset(0)
 {
+	const Technique *tech = object.get_technique();
+	const Technique::PassMap &passes = tech->get_passes();
+	for(Technique::PassMap::const_iterator i=passes.begin(); i!=passes.end(); ++i)
+	{
+		const Program *shprog = i->second.get_shader_program();
+		if(!shprog)
+			throw invalid_argument("InstanceArray::InstanceArray");
+
+		int loc = shprog->get_attribute_location("instance_transform");
+		if(matrix_location<0)
+			matrix_location = loc;
+		else if(loc!=matrix_location)
+			throw invalid_argument("InstanceArray::InstanceArray");
+	}
+
 	if(ARB_vertex_array_object && ARB_instanced_arrays && ARB_draw_instanced)
 	{
-		instance_data = new VertexArray((ATTRIB4,12, ATTRIB4,13, ATTRIB4,14));
+		instance_data = new VertexArray((ATTRIB4,matrix_location, ATTRIB4,matrix_location+1, ATTRIB4,matrix_location+2));
 		const VertexFormat &fmt = instance_data->get_format();
-		matrix_offset = fmt.offset(make_indexed_component(ATTRIB4, 12));
+		matrix_offset = fmt.offset(make_indexed_component(ATTRIB4, matrix_location));
 
 		instance_buffer = new Buffer(ARRAY_BUFFER);
 		instance_data->use_buffer(instance_buffer);
@@ -112,9 +128,8 @@ void InstanceArray::render(Renderer &renderer, const Tag &tag) const
 		for(vector<ObjectInstance *>::const_iterator i=instances.begin(); i!=instances.end(); ++i)
 		{
 			const Matrix &m = *(*i)->get_matrix();
-			glVertexAttrib4f(12, m(0, 0), m(0, 1), m(0, 2), m(0, 3));
-			glVertexAttrib4f(13, m(1, 0), m(1, 1), m(1, 2), m(1, 3));
-			glVertexAttrib4f(14, m(2, 0), m(2, 1), m(2, 2), m(2, 3));
+			for(unsigned j=0; j<3; ++j)
+				glVertexAttrib4f(matrix_location+j, m(j, 0), m(j, 1), m(j, 2), m(j, 3));
 			(*i)->render(renderer, tag);
 		}
 	}
diff --git a/source/instancearray.h b/source/instancearray.h
index ffba39e0..627051f7 100644
--- a/source/instancearray.h
+++ b/source/instancearray.h
@@ -42,6 +42,7 @@ private:
 	VertexArray *instance_data;
 	Buffer *instance_buffer;
 	VertexSetup *vtx_setup;
+	int matrix_location;
 	unsigned matrix_offset;
 
 public: