Heightmap probing is now rendered in real time.

render.cpp

@@ -339,6 +339,8 @@ void grbl::program_renderer::initialize_program_buffers() {
 }
 
 GLsizei grbl::program_renderer::update_model_vbo(const grbl::program& pgm) {
+    if (!pgm.is_loaded) return 0;
+
     static auto movement_re = std::regex(R"(([gG]0*1?\s+|[xXyYzZ]\s*[0-9\.\-]+))");
     bool is_tool_on = false;
 
@@ -428,6 +430,9 @@ void grbl::program_renderer::update_grid(const grbl::heightmap& grid) {
 
     glm::vec4 color = {0.5, 0.3, 0, 1};
 
+    // this should only be called whenever the grid changes
+    // therefor it should be called each and every time we
+    // probe a new location. let's check that.
     std::vector<float> buffer_data;
 
     for (int y = 0; y < grid.y_segments; y++) {
@@ -466,7 +471,7 @@ void grbl::program_renderer::update_grid(const grbl::heightmap& grid) {
     heightmap_vertices_count = buffer_data.size() * sizeof(float) / size_of_vertex_in_bytes;
 
     glBindBuffer(GL_ARRAY_BUFFER, heightmap_vbo_id);
-    glBufferData(GL_ARRAY_BUFFER, sizeof(float) * buffer_data.size(), buffer_data.data(), GL_STATIC_DRAW);
+    glBufferData(GL_ARRAY_BUFFER, sizeof(float) * buffer_data.size(), buffer_data.data(), GL_DYNAMIC_DRAW);
 }
 
 void grbl::program_renderer::initialize_heightmap_buffers() {