X-Git-Url: http://git.tdb.fi/?a=blobdiff_plain;f=source%2Frender%2Finstancearray.h;h=d793ce2ed229cd8159ac9fc2504c9c1d0472a854;hb=9e63512930bc7dace6dc169c65161961e5dcfcf6;hp=8f5c73225519a374623c818b6298cdc55a308471;hpb=5bb193f930fb8738d099d630c4d625d82c1215b5;p=libs%2Fgl.git

diff --git a/source/render/instancearray.h b/source/render/instancearray.h
index 8f5c7322..d793ce2e 100644
--- a/source/render/instancearray.h
+++ b/source/render/instancearray.h
@@ -15,10 +15,14 @@ class Object;
 class ObjectInstance;
 
 /**
-Renders multiple instances of an Object in an efficient manner.  If instanced
-rendering is supported, only one draw call per Batch needs to be issued.
+Renders multiple instances of an Object in an efficient manner.
 
-Changing the Mesh of the Object while an InstanceArray exists is not supported.
+The instance specific transform is passed to the shader in an attribute with
+the name instance_transform.  The attribute should have the type vec4[3].  Each
+elements of the array corresponds to a row of the transform matrix.
+
+If the Mesh or Technique of the Object is changed during the lifetime of the
+InstanceArray, behaviour is undefined.
 */
 class InstanceArray: public Renderable
 {
@@ -40,10 +44,10 @@ private:
 	const Object &object;
 	std::vector<ObjectInstance *> instances;
 	VertexArray instance_data;
-	Buffer *instance_buffer;
+	Buffer *instance_buffer = 0;
 	VertexSetup vtx_setup;
-	int matrix_location;
-	unsigned matrix_offset;
+	int matrix_location = -1;
+	unsigned matrix_offset = 0;
 
 public:
 	InstanceArray(const Object &);
@@ -51,6 +55,8 @@ public:
 
 	void set_matrix_attribute(const std::string &);
 
+	/** Adds a new instance to the array.  The instance class must have a
+	constructor taking a const reference to Object as its sole parameter. */
 	template<typename T = ObjectInstance>
 	T &append();
 private: