diff --git a/src/hexgame.cpp b/src/hexgame.cpp
index 5db03c8..9f1f886 100644
--- a/src/hexgame.cpp
+++ b/src/hexgame.cpp
@@ -211,6 +211,8 @@ updateHexConeFill(int32 x, int32 y)
 			
 			for (hex_info &h : *g_game_state->hex_array)
 			{
+				// TODO: define a system of linear inequalities in hex-space to represent
+				// 	cones/arbitrary polygons
 				if (&h == g_game_state->start_hex)
 				{
 					continue;
diff --git a/src/renderer.h b/src/renderer.h
index d64a2fa..6ae4d33 100644
--- a/src/renderer.h
+++ b/src/renderer.h
@@ -113,6 +113,7 @@ void fillColorBuffer(GLfloat buf[], int len, std::vector<hex_info> *hexes);
 void fillHexLineBuffer(GLfloat buf[], int len, std::vector<hex_info>* hexes);
 bool checkGLBufferSize(GLenum buf_type, int expected_size, int line_num);
 bool initGLBufferObject(gl_buffer* buf_obj, int len, GLenum usage, GLfloat data[]);
+void drawRenderGroup(gl_render_group* rg, GLenum draw_mode, bool update_vertex_data);
 
 bool
 initRenderer(SDL_Handles &handles, v2i vpDims)
@@ -416,58 +417,59 @@ openglDebugCallback(GLenum source, GLenum type, GLuint id, GLenum severity,
 }
 
 void
-renderFrame(std::vector<hex_info> *hexes)
+drawRenderGroup(gl_render_group* rg, GLenum draw_mode, bool update_vertex_data = false)
 {
-	glClearColor(g_clear_col.R, g_clear_col.G, g_clear_col.B, g_clear_col.A);
-	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
+	glUseProgram(rg->program_id);
+	// Send our transformation to the currently bound shader, in the "g_MVP" uniform
+	glUniformMatrix4fv(rg->matrix_id, 1, GL_FALSE, &g_scene_matrices.MVP[0][0]);
+	
+	// 1st attribute buffer : vertices
+	glEnableVertexAttribArray(0);
+	glBindBuffer(GL_ARRAY_BUFFER, rg->vertex_buffer.buffer_id);
+	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*) 0);
+	
+	if (update_vertex_data)
+	{
+		glBufferSubData(GL_ARRAY_BUFFER, 0, rg->vertex_buffer.buffer_len * sizeof(GLfloat),
+			rg->vertex_buffer.buffer);
+	}
 
-	// filled hexes
+	// 2nd attribute buffer : colors
+	if (rg->color_buffer.buffer)
 	{
-		// TODO: learn how to use VAOs instead of these calls to glVertexAttribPointer
-		// 	https://www.khronos.org/opengl/wiki/Vertex_Specification#Vertex_Array_Object
-		gl_render_group* rg = &g_filled_hex_render_group;
-		glUseProgram(rg->program_id);
-		// Send our transformation to the currently bound shader, in the "g_MVP" uniform
-		glUniformMatrix4fv(rg->matrix_id, 1, GL_FALSE, &g_scene_matrices.MVP[0][0]);
-		
-		// 1st attribute buffer : vertices
-		glEnableVertexAttribArray(0);
-		glBindBuffer(GL_ARRAY_BUFFER, rg->vertex_buffer.buffer_id);
-		glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*) 0);
-		
-		// 2nd attribute buffer : colors
 		glEnableVertexAttribArray(1);
 		glBindBuffer(GL_ARRAY_BUFFER, rg->color_buffer.buffer_id);
 		glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 0, (void*) 0);
 		
-		// get new colors every frame
-		fillColorBuffer(rg->color_buffer.buffer, rg->color_buffer.buffer_len, hexes);
+		// TODO: maybe add an option to not send color data every frame?
 		glBufferSubData(GL_ARRAY_BUFFER, 0, rg->color_buffer.buffer_len * sizeof(GLfloat),
 				rg->color_buffer.buffer);
-		// draw
-		glDrawArrays(GL_TRIANGLES, 0, rg->vertex_buffer.buffer_len / 3);
-		
-		// cleanup
-		glDisableVertexAttribArray(0);
-		glDisableVertexAttribArray(1);
 	}
+	// draw
+	glDrawArrays(draw_mode, 0, rg->vertex_buffer.buffer_len / 3);
+	
+	// cleanup
+	glDisableVertexAttribArray(0);
+	if (rg->color_buffer.buffer)
+		glDisableVertexAttribArray(1);
+}
+
+void
+renderFrame(std::vector<hex_info> *hexes)
+{
+	glClearColor(g_clear_col.R, g_clear_col.G, g_clear_col.B, g_clear_col.A);
+	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
+
+	// filled hexes
+
+	// get new colors every frame
+	gl_render_group* rg = &g_filled_hex_render_group;
+	fillColorBuffer(rg->color_buffer.buffer, rg->color_buffer.buffer_len, hexes);
+	drawRenderGroup(rg, GL_TRIANGLES);
 
 	// hex lines
-	// TODO: conpress these calls into helper function
-	{
-		gl_render_group* rg = &g_hex_line_render_group;
-		glUseProgram(rg->program_id);
-		// Send our transformation to the currently bound shader, in the "g_MVP" uniform
-		glUniformMatrix4fv(rg->matrix_id, 1, GL_FALSE, &g_scene_matrices.MVP[0][0]);
-
-		// 1st attribute buffer : vertices
-		GLuint attrib_index = 0; // TODO: line buffer doesn't render if this is anything other than 0
-		glEnableVertexAttribArray(attrib_index);
-		glBindBuffer(GL_ARRAY_BUFFER, rg->vertex_buffer.buffer_id);
-		glVertexAttribPointer(attrib_index, 3, GL_FLOAT, GL_FALSE, 0, (void*) 0);
-		glDrawArrays(GL_LINES, 0, rg->vertex_buffer.buffer_len / 3);
-		glDisableVertexAttribArray(0);
-	}
+
+	drawRenderGroup(&g_hex_line_render_group, GL_LINES);
 }
 
 void
@@ -509,19 +511,7 @@ renderDebug(hex_info *start_hex, hex_info *current_hex)
 	for (int i = 0; i < 12; i++)
 		rg->vertex_buffer.buffer[i] = buf[i];
 
-	// TODO: conpress these calls into helper function
-	glUseProgram(rg->program_id);
-	// Send our transformation to the currently bound shader, in the "g_MVP" uniform
-	glUniformMatrix4fv(rg->matrix_id, 1, GL_FALSE, &g_scene_matrices.MVP[0][0]);
-
-	glEnableVertexAttribArray(0);
-	glBindBuffer(GL_ARRAY_BUFFER, rg->vertex_buffer.buffer_id);
-	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*) 0);
-	// send new vertex data
-	glBufferSubData(GL_ARRAY_BUFFER, 0, rg->vertex_buffer.buffer_len * sizeof(GLfloat),
-		rg->vertex_buffer.buffer);
-	glDrawArrays(GL_LINE_LOOP, 0, rg->vertex_buffer.buffer_len / 3);
-	glDisableVertexAttribArray(0);
+	drawRenderGroup(rg, GL_LINE_LOOP, true);
 }
 
 void