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

2 files changed, 43 insertions, 0 deletions

diff --git a/intern/cycles/kernel/shaders/CMakeLists.txt b/intern/cycles/kernel/shaders/CMakeLists.txt
index 6ec651a96d8..b28d017c1c2 100644
--- a/intern/cycles/kernel/shaders/CMakeLists.txt
+++ b/intern/cycles/kernel/shaders/CMakeLists.txt
@@ -39,6 +39,7 @@ set(SRC_OSL
 	node_principled_volume.osl
 	node_holdout.osl
 	node_hsv.osl
+	node_ies_light.osl
 	node_image_texture.osl
 	node_invert.osl
 	node_layer_weight.osl
diff --git a/intern/cycles/kernel/shaders/node_ies_light.osl b/intern/cycles/kernel/shaders/node_ies_light.osl
new file mode 100644
index 00000000000..a0954e3a444
--- /dev/null
+++ b/intern/cycles/kernel/shaders/node_ies_light.osl
@@ -0,0 +1,42 @@
+/*
+ * Copyright 2011-2015 Blender Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "stdosl.h"
+#include "node_texture.h"
+
+/* IES Light */
+
+shader node_ies_light(
+	int use_mapping = 0,
+	matrix mapping = matrix(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
+	int slot = 0,
+	float Strength = 1.0,
+	point Vector = I,
+	output float Fac = 0.0)
+{
+	point p = Vector;
+
+	if (use_mapping) {
+		p = transform(mapping, p);
+	}
+
+	p = normalize(p);
+
+	float v_angle = acos(-p[2]);
+	float h_angle = atan2(p[0], p[1]) + M_PI;
+
+	Fac = Strength * texture(format("@l%d", slot), h_angle, v_angle);
+}