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RGB Curves node kills HDR values?
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tested on Windows 8 Lenovo G580 laptop
Processor Intel(R) Pentium(R) CPU B980 @ 2.40GHz
Memory (RAM) 4.00 GB
Graphics Intel(R) HD Graphics

Blender 2.68a r58537
Blender 2.76b 2015-11-03 10:56 f337fea

this seems so profound it might be my error somewhere: running an HDRI through RGB Curves kills HDR values no matter if RGB Curves node > Clipping Options > "Use Clipping" is on or off

setting RGB Curves fac to -1 somewhat mitigates the problem but puts the whole node into "reverse" (ie: all curves inverted) and is not a precise fix: the HDR values still seem somewhat affected

Hue/Sat, Brightness/Contrast and MixRGB all seem fine

Greg Zaal does not see the problem on his system - Sean Kennedy does not see the problem on his Mac system but does see some mild disturbance to the effect of the HDR

to reproduce: set up a World environment texture for Image-Based-Lighting using an HDRI (I used Greg Zaal's HDRI Haven images to test), run the colour output of the Environment Texture node through an RGB Curves node - make sure the RGB Curves node's Use Clipping option is turned off - put the viewport in render draw mode and/or render the image - the HDR values of the Environment do not correctly light the scene - change the RGB Curves node's fac to -1 - HDR values now light the scene but not exactly the same as if RGB Curves node was not in the node tree - remove the RGB Curves node from the node tree - the HDR values correctly light the scene

forgive me if this is something painfully obvious that I'm missing - seems so profound I can't believe it's a bug but I can't seem to fix it at my end

demo blend attached - open in B276b, put viewport in render draw mode, packed HDRI does not light the scene correctly - bypass RGB Curves node in node editor - HDRI now lights the scene correctly

also attached: a pair of demo images with and without RGB Curves node in node tree

Event Timeline

Hello. Here on a Windows 7 Pro 64bits OS, with Blender 2.76b 64bit official release I get the same behavior when inserting the RGB Curve node, despite having set the HDR image to be read as non-color data (I though it might be the source of the problem, but it wasn't).

Thomas Dinges (dingto) changed the task status from Unknown Status to Resolved.Mar 11 2016, 3:02 PM
Thomas Dinges (dingto) claimed this task.

That has been fixed, please use Blender 2.77 RC2. See "Vector curves now supports dynamic range input/output"