Cycles: Add Support for IES files as textures for light strength

This patch adds support for IES files, a file format that is commonly used to store the directional intensity distribution of light sources.
The new IES node is supposed to be plugged into the Strength input of the Emission node of the lamp.

Since people generating IES files do not really seem to care about the standard, the parser is flexible enough to accept all test files I have tried.
Some common weirdnesses are distributing values over multiple lines that should go into one line, using commas instead of spaces as delimiters and adding various useless stuff at the end of the file.

The user interface of the node is similar to the script node, the user can either select an internal Text or load a file.
Internally, IES files are handled similar to Image textures: They are stored in slots by the LightManager and each unique IES is assigned to one slot.

The local coordinate system of the lamp is used, so that the direction of the light can be changed. For UI reasons, it's usually best to add an area light,
rotate it and then change its type, since especially the point light does not immediately show its local coordinate system in the viewport.

Reviewers: #cycles, dingto, sergey, brecht

Reviewed By: #cycles, dingto, brecht

Subscribers: OgDEV, crazyrobinhood, secundar, cardboard, pisuke, intrah, swerner, micah_denn, harvester, gottfried, disnel, campbellbarton, duarteframos, Lapineige, brecht, juicyfruit, dingto, marek, rickyblender, bliblubli, lockal, sergey

Differential Revision: https://developer.blender.org/D1543

1 files changed, 122 insertions, 0 deletions

diff --git a/intern/cycles/render/light.cpp b/intern/cycles/render/light.cpp
index 8dec7e4ea64..f0824ef4319 100644
--- a/intern/cycles/render/light.cpp
+++ b/intern/cycles/render/light.cpp
@@ -25,6 +25,8 @@
 #include "render/shader.h"
 
 #include "util/util_foreach.h"
+#include "util/util_hash.h"
+#include "util/util_path.h"
 #include "util/util_progress.h"
 #include "util/util_logging.h"
 
@@ -175,6 +177,9 @@ LightManager::LightManager()
 
 LightManager::~LightManager()
 {
+	foreach(IESSlot *slot, ies_slots) {
+		delete slot;
+	}
 }
 
 bool LightManager::has_background_light(Scene *scene)
@@ -858,6 +863,9 @@ void LightManager::device_update(Device *device, DeviceScene *dscene, Scene *sce
 	device_update_background(device, dscene, scene, progress);
 	if(progress.get_cancel()) return;
 
+	device_update_ies(dscene);
+	if(progress.get_cancel()) return;
+
 	if(use_light_visibility != scene->film->use_light_visibility) {
 		scene->film->use_light_visibility = use_light_visibility;
 		scene->film->tag_update(scene);
@@ -872,6 +880,7 @@ void LightManager::device_free(Device *, DeviceScene *dscene)
 	dscene->lights.free();
 	dscene->light_background_marginal_cdf.free();
 	dscene->light_background_conditional_cdf.free();
+	dscene->ies_lights.free();
 }
 
 void LightManager::tag_update(Scene * /*scene*/)
@@ -879,5 +888,118 @@ void LightManager::tag_update(Scene * /*scene*/)
 	need_update = true;
 }
 
+int LightManager::add_ies_from_file(ustring filename)
+{
+	string content;
+	/* If the file can't be opened, call with an empty string */
+	path_read_text(filename.c_str(), content);
+
+	return add_ies(ustring(content));
+}
+
+int LightManager::add_ies(ustring content)
+{
+	uint hash = hash_string(content.c_str());
+
+	thread_scoped_lock ies_lock(ies_mutex);
+
+	/* Check whether this IES already has a slot. */
+	size_t slot;
+	for(slot = 0; slot < ies_slots.size(); slot++) {
+		if(ies_slots[slot]->hash == hash) {
+			ies_slots[slot]->users++;
+			return slot;
+		}
+	}
+
+	/* Try to find an empty slot for the new IES. */
+	for(slot = 0; slot < ies_slots.size(); slot++) {
+		if(ies_slots[slot]->users == 0 && ies_slots[slot]->hash == 0) {
+			break;
+		}
+	}
+
+	/* If there's no free slot, add one. */
+	if(slot == ies_slots.size()) {
+		ies_slots.push_back(new IESSlot());
+	}
+
+	ies_slots[slot]->ies.load(content);
+	ies_slots[slot]->users = 1;
+	ies_slots[slot]->hash = hash;
+
+	need_update = true;
+
+	return slot;
+}
+
+void LightManager::remove_ies(int slot)
+{
+	thread_scoped_lock ies_lock(ies_mutex);
+
+	if(slot < 0 || slot >= ies_slots.size()) {
+		assert(false);
+		return;
+	}
+
+	assert(ies_slots[slot]->users > 0);
+	ies_slots[slot]->users--;
+
+	/* If the slot has no more users, update the device to remove it. */
+	need_update |= (ies_slots[slot]->users == 0);
+}
+
+void LightManager::device_update_ies(DeviceScene *dscene)
+{
+	/* Clear empty slots. */
+	foreach(IESSlot *slot, ies_slots) {
+		if(slot->users == 0) {
+			slot->hash = 0;
+			slot->ies.clear();
+		}
+	}
+
+	/* Shrink the slot table by removing empty slots at the end. */
+	int slot_end;
+	for(slot_end = ies_slots.size(); slot_end; slot_end--) {
+		if(ies_slots[slot_end-1]->users > 0) {
+			/* If the preceding slot has users, we found the new end of the table. */
+			break;
+		}
+		else {
+			/* The slot will be past the new end of the table, so free it. */
+			delete ies_slots[slot_end-1];
+		}
+	}
+	ies_slots.resize(slot_end);
+
+	if(ies_slots.size() > 0) {
+		int packed_size = 0;
+		foreach(IESSlot *slot, ies_slots) {
+			packed_size += slot->ies.packed_size();
+		}
+
+		/* ies_lights starts with an offset table that contains the offset of every slot,
+		 * or -1 if the slot is invalid.
+		 * Following that table, the packed valid IES lights are stored. */
+		float *data = dscene->ies_lights.alloc(ies_slots.size() + packed_size);
+
+		int offset = ies_slots.size();
+		for(int i = 0; i < ies_slots.size(); i++) {
+			int size = ies_slots[i]->ies.packed_size();
+			if(size > 0) {
+				data[i] = __int_as_float(offset);
+				ies_slots[i]->ies.pack(data + offset);
+				offset += size;
+			}
+			else {
+				data[i] = __int_as_float(-1);
+			}
+		}
+
+		dscene->ies_lights.copy_to_device();
+	}
+}
+
 CCL_NAMESPACE_END