diff --git a/Aquaria/CurrentRender.cpp b/Aquaria/CurrentRender.cpp
index 676c066..06b89fa 100644
--- a/Aquaria/CurrentRender.cpp
+++ b/Aquaria/CurrentRender.cpp
@@ -70,7 +70,11 @@ void CurrentRender::onUpdate(float dt)
 		size_t usedsize;
 		do
 		{
-			float *p = (float*)vbo.beginWrite(GPUBUFTYPE_VEC2_TC_RGBA, bytes, GPUACCESS_DEFAULT);
+			// Usually we write much less data than maximally possible to the GPU,
+			// because most segments are off-screen and not visible.
+			// The hostcopy flag accumulates the used data in the host heap
+			// and only uploads what is necessary in the end
+			float *p = (float*)vbo.beginWrite(GPUBUFTYPE_VEC2_TC_RGBA, bytes, GPUACCESS_HOSTCOPY);
 			verts = writeVBOData(p);
 			usedsize = verts * 8 * sizeof(float);
 		}
@@ -109,9 +113,6 @@ size_t CurrentRender::writeVBOData(float *p)
 			if (diff.isZero())
 				continue;
 
-			float len = diff.getLength2D();
-			float texScale = len/256.0f;
-
 			if (isTouchingLine(p1, p2, dsq->screenCenter, dsq->cullRadius+w2))
 			{
 				Vector pl = diff.getPerpendicularLeft();
@@ -132,6 +133,8 @@ size_t CurrentRender::writeVBOData(float *p)
 
 				const float ao = P->animOffset;
 				const float a = P->amount;
+				const float len = diff.getLength2D();
+				const float texScale = len/256.0f;
 
 				/* This builds a structure like this:
 				a = 0 alpha
diff --git a/BBGE/VertexBuffer.cpp b/BBGE/VertexBuffer.cpp
index a063ece..ed0d303 100644
--- a/BBGE/VertexBuffer.cpp
+++ b/BBGE/VertexBuffer.cpp
@@ -141,12 +141,15 @@ bool DynamicGPUBuffer::_commitWrite(size_t used)
         // -> didn't map, but wrote to host memory. upload it.
         assert(_h_data);
         assert(used <= _h_cap);
-        if(used <= _d_cap)
-            glBufferSubDataARB(_gl_binding, 0, used, _h_data); // update existing buffer
-        else
+        if(used)
         {
-            _d_cap = used;
-            glBufferDataARB(_gl_binding, used, _h_data, _gl_usage); // alloc new buffer
+            if(used <= _d_cap)
+                glBufferSubDataARB(_gl_binding, 0, used, _h_data); // update existing buffer
+            else
+            {
+                _d_cap = used;
+                glBufferDataARB(_gl_binding, used, _h_data, _gl_usage); // alloc new buffer
+            }
         }
     }
     // else nothing to do
@@ -168,6 +171,7 @@ void DynamicGPUBuffer::upload(BufDataType type, const void* data, size_t size)
             last = id;
             glBindBufferARB(_gl_binding, id);
         }
+        _d_cap = size;
         glBufferDataARB(_gl_binding, size, data, _gl_usage);
     }
     else