Brightness/Contrast Node for Cycles

Contrast helps to adjust IBL (HDR images used for background lighting).
Note: In the UI we are caling it Bright instead of Brightness. This copy what Blender composite is doing.
Note2: the algorithm we are using produces pure black when contrast is 100. I'm not a fan of that, but it's a division by zero. I would like to look at other algorithms (what gimp does for example). But that would be only after 2.62.

1 files changed, 57 insertions, 0 deletions

diff --git a/intern/cycles/kernel/svm/svm_brightness.h b/intern/cycles/kernel/svm/svm_brightness.h
new file mode 100644
index 00000000000..698899ffd60
--- /dev/null
+++ b/intern/cycles/kernel/svm/svm_brightness.h
@@ -0,0 +1,57 @@
+/*
+ * Copyright 2011, Blender Foundation.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+CCL_NAMESPACE_BEGIN
+
+__device void svm_node_brightness(ShaderData *sd, float *stack, uint in_color, uint out_color, uint node)
+{
+	uint bright_offset, contrast_offset;
+	float3 color = stack_load_float3(stack, in_color);
+
+	decode_node_uchar4(node, &bright_offset, &contrast_offset, NULL, NULL);
+	float brightness = stack_load_float(stack, bright_offset);
+	float contrast  = stack_load_float(stack, contrast_offset);
+
+	brightness *= 1.0f/100.0f;
+	float delta = contrast * (1.0f/200.0f);
+	float a = 1.0f - delta * 2.0f;
+	float b;
+
+	/*
+	* The algorithm is by Werner D. Streidt
+	* (http://visca.com/ffactory/archives/5-99/msg00021.html)
+	* Extracted of OpenCV demhist.c
+	*/
+	if (contrast > 0.0f) {
+		a = (a > 0.0f? (1.0f / a): 0.0f);
+		b = a * (brightness - delta);
+	}
+	else {
+		delta *= -1.0f;
+		b = a * (brightness + delta);
+	}
+
+	color.x = a*color.x + b;
+	color.y = a*color.y + b;
+	color.z = a*color.z + b;
+
+	if (stack_valid(out_color))
+		stack_store_float3(stack, out_color, color);
+}
+
+CCL_NAMESPACE_END