Changes between LC and LH revs?

Hello again,

Following on from http://forum.irendernxt.com/forum/topics/editing-nxtimage-directly-... (different problem, different thread) I'd like to know why these images are not virtually (visually) identical.

This was done with rev LC02 or LC13:

And this was done with LH27:

Objects have been moved around slightly and material tweaks, but the lighting should be the same. eg I didn't change the intensity or colour or direction of any lights. In the above image 2 lights are on (both face upward and reflect off the white ceiling).

Most notable is the intensity of the light in the top-right corner which is much brighter/harsher in the second image (like it is a 750w bulb rather then 75w). But the new Query Lights feature (thanx for the fix in LH30) confirms that the lights are correct and are still 75w.

Below is a difference map so it is more obvious where the changes are:The red bits are the important bits. A lot of that red is attributable to the fact that I changed the material from a matted white to a shiny silver. But as you can see, both the top left and top right have a lot of red, indicating that these lights are much brighter then the image I made back in LCxx.

So, have I inadvertently changed something in lights and not realized it? Maybe I didn't get all the Setup Options set the same? (studio lighting, indirect lighting, all that jazz) or has something changed in the rendering engines between these two which is causing the disparity?

regards,

-randall

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Permalink Reply by Randy S on September 3, 2012 at 3:08am

PS- I forgot to mention that the size/intensity of the sun is different between the two as well.

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Permalink Reply by Rich Hart on September 4, 2012 at 12:18pm

One nice thing about saving renderings as jpegs is that we save most of the settings for the rendering in the jpg file. That way you can load the same settings used is a previous rendering by just importing the settings from that previous rendering.

It also lets us compare 2 renderings to see what settings have changed.

We use a piece of software here called Araxis Merge, which lets us compare 2 files, or 2 sets of data copied from the clipboard, so we can just open the jpegs, using the program RPSImageQuery.exe in the bin_nXt folder in the folder where we install IRender nXt, and copy the settings to compare them, as below.

Comparing the settings embedded in the jpegs that you posted, I see that the older rendering was done with version LB 29, and I can see that a different version of the AccuRender toolkit was used back then:

Paging further down the only real differences I see are that reflective bounces have been increased to 4, and that "bir_process_invisible_lights" is turned on for the LH24 version, so hidden lights are being processed in the later version...but it's still a total of 5 lights being processed, so that might not be the change.

The light Query dialog, doesn't yet show if the light intensity has been changed by the "Override Light Intensity" settings for any of the components that the light might be nested in.

Could you send me the current and model and let me take a look?

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Permalink Reply by Randy S on September 4, 2012 at 12:33pm

Hi Rich,

I am happy to send it up, although the problem seems to have sorted itself out although I'm not exactly 100% sure why.... Usually when I do a rendering I turn all the lights on, and then use the lighting channels in the renderer to tweak them. But I seem to recall turning some lights off before doing the rendering (eg via Setup Options | Lights). Would that account for it?

As a general aside, I never really understood the "Average Luminance" setting in the Lighting channel dlg. (in my renders, I always set this to 11.64). But it is always something else when I first render an image. the value doesn't seem to "stick". Is this a relative value to the intensity of the other lights in the model? In other words, if it is set to 11.64 but I turn off all lights but 1 - should I expect to get the same rendering as a model that has all lights on and I turn them off after the rendering starts?

Let me know if ya still want this model.

cheers