diff --git a/render.cpp b/render.cpp
index ece2769..a3cca04 100644
--- a/render.cpp
+++ b/render.cpp
@@ -442,11 +442,20 @@ GLsizei grbl::program_renderer::update_model_vbo(const grbl::program &pgm) {
                     add_line(buffer_data, line->start, rapid_color, line->end, rapid_color);
                 else
                     add_line(buffer_data, line->start, feed_color, line->end, feed_color);
+
+                if (!line->rapid) {
+                    update_model_extents(line->start);
+                    update_model_extents(line->end);
+                }
+
             } else if (arc != nullptr) {
                 auto pieces = arc->split(0.1);
                 for (auto &p: pieces) {
                     // transform arc to line
                     add_line(buffer_data, p->start, feed_color, p->end, feed_color);
+
+                    update_model_extents(p->start);
+                    update_model_extents(p->end);
                 }
             }
         }
@@ -537,6 +546,17 @@ void grbl::program_renderer::initialize_heightmap_buffers() {
     glBindVertexArray(0);
 }
 
+void grbl::program_renderer::update_model_extents(glm::vec3 point) {
+    min_pos.x = std::min(min_pos.x, point.x);
+    min_pos.y = std::min(min_pos.y, point.y);
+    min_pos.z = std::min(min_pos.z, point.z);
+
+    max_pos.x = std::max(max_pos.x, point.x);
+    max_pos.y = std::max(max_pos.y, point.y);
+    max_pos.z = std::max(max_pos.z, point.z);
+
+}
+
 std::string get_shader_info_log(GLuint id) {
     GLint log_length = 0;
     glGetShaderiv(id, GL_INFO_LOG_LENGTH, &log_length);
diff --git a/render.h b/render.h
index 2883b78..5d3814b 100644
--- a/render.h
+++ b/render.h
@@ -22,6 +22,7 @@ public:
     void update_grid(const grbl::heightmap& grid);
 private:
     GLsizei update_model_vbo(const grbl::program& pgm);
+    void update_model_extents(glm::vec3 point);
 
     GLuint spindle_vbo_id;
     GLuint spindle_vao_id;