Add support for spot lights with a fixed direction in model space

src/renderlogic.cpp

@@ -208,7 +208,9 @@ void renderNode(SceneNode* node, Gloom::Shader* parent_shader, vector<NodeDistSh
             uint id = node->lightID;
             lights[id].position          = vec3(node->MV * vec4(vec3(0.0), 1.0));
             lights[id].is_spot           = node->nodeType == SPOT_LIGHT;
-            lights[id].spot_direction    = node->spot_direction; // MV space
+            lights[id].spot_direction    = (node->transform_spot)
+                ? node->spot_direction                                   // MV space
+                : vec3(node->MVnormal * vec4(node->spot_direction, 1.0));// Model space
             lights[id].spot_cuttof_cos   = node->spot_cuttof_cos;
             lights[id].attenuation       = node->attenuation;
             lights[id].color             = node->light_color;

src/sceneGraph.hpp

@@ -57,6 +57,7 @@ struct SceneNode {
 	float spot_cuttof_cos = glm::cos(glm::radians(1.5));
 	vec3 spot_direction = vec3(0.0); // in MV space, must be normalized, automatically updated by spot_target
 	SceneNode* spot_target  = nullptr; // spot will follow this node
+	bool transform_spot = false; // if true, spot_direction will be in model space.
 
 	// The node's position and rotation relative to its parent
 	vec3 position = vec3(0, 0, 0);