View Full Version : Image procesing filters threshold dilemma...

11 November 2002, 02:18 PM
Has anyone else ever noticed this...

When working with image processing filters, I've noticed that they don't seem to acknowledge values which excede 100%.

For instance, I'm working on an object which had a bright luminous point which travels across it. I've set up a travelling image map with a bright strip which travels along a pipe. The whole pipe is very luminous, but this particular strip is set to 500% luminosity. Rendering it straight out definitely shows that this spot is very noticably brighter than the parts which are only set to values not exceeding 100%. Now, that shows that Lightwave definitely does make allowances in the surface editor for values which are typically "out of range", in the traditional sense. We all know this already.

However, my problem is that now I want to use the Corona filter to make that bright spot (and not any other part of the object) glow nicely. I set up the filter, and entered in 500% as the threshold value. However, all the values which are near to 100% in the other areas are now also being affected by the filter. It's like it cannot see values above 100%.

Is this the case, or is there something I can do to alter this???
Any insight would be most appreciated :)

11 November 2002, 02:22 PM
I was under the impression that threshhold limited the effect.

11 November 2002, 02:25 PM
Yes it does, but I don't want it to affect anything under 500%, in other words, I don't want the rest of the pipe affected, only the part that is 500% luminous.

However, it doesn't seem to acknowledge that. It is giving everything around 100% luminosity a glow instead of just the amount exceeding 500%. It's like it doesn't have a range over 100.

I have however managed to fix it (kind of) using stuff in the Corona texture editor :)

So no worries for now...

Actually, dammit!! I thought I'd fixed it but it's still not working :annoyed:


11 November 2002, 05:59 PM
Looks like the threshold only REALLY works in the other direction. ie <100%.

I guess they only felt that you would want it to dip below 100% and not limit it to above 101%.

Your would think that more of the NewTek made/aquired filters would respect HDR values.

A work around may be (theory, not tested):

Add an image saver filter in the list (to save a clean render)

Add HDRExpose to remap to 0-100%

Adjust corona's threshold to use the remapped values and set the effect only option in corona.

Composite the results.

You may even be able to add Texture Filter to the image filter list to add the corona file and have LW do the entire process as a rendered frame. Load in the rendered seq and the corona as image sequence and the Tex filter using them as image map layers. This will require a manual render of one from though.

11 November 2002, 06:36 PM
I occasionally peruse the Lightave Docs, after having read them twice when I first started, just to see what I missed or didn't understand. I ran across the Special Buffers on the surface editor. For surface specific Image processes, you can apply the special buffer to exceed the normal capacity of certain Image filters.

This may be a shot in the dark, but I have a feeling it will help some.

Re-read the section in the Docs about Special buffers. It makes specific reference to the corona filter.specific

11 November 2002, 10:05 PM
Leigh - why not to split surfaces with above 500% luminosity and under ?

11 November 2002, 04:57 PM
Thanks for all the suggestions everybody :thumbsup:

I'll try and fix this...

Eugeny - unfortunately it's not as simple as that, as the luminosity is set with a very detailed gradient, and I cannot seperate them into 2 surfaces because of the kind of object that it is :sad: But thanks for the suggestion anyway, always appreciated :)

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