BrushWave and particle flickering

On January 7th, 2009, I wrote an E-Mail to Yannick Tholomier concerning BrushWave's problem with particle flickering in animations. I post it here for reference, as it might be interesting for other users as well.

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Perhaps you have looked at my description how the plugin works; I let LightWave render the scene normally, and all the color information for my brushes is then looked up in this image.

This is a very flexible approach, as it allows all different kind of renderings to be turned into a painterly style, BUT is has a severe drawback: sometimes I would need more information than there is available in the image of the ordinary rendering.

I will give you one example – please stay with me, I hope I am able to describe the problem clearly enough:

Suppose you have an object with huge brush strokes; let's say the strokes are about 20×20 pixels. I get the color of each stroke by finding its center point (1 pixel!) and looking up the color of this center point in the first rendering (I could also take the average color around this region, but that's not the point now). So far, so good.

Now there's another small object (e.g. 10×10 pixels) moving in front of this object. This object will sometimes move exactly over the center-point of one of the strokes of the object in the background. Now I have a problem, as I don't know in which color to paint the huge stroke – I do not have any information about it!

Now one could propose a workaround: why don't I remember the color of the particle BEFORE it was occluded? Fair enough – but what if this is a still image? Even if there's no flickering in still images (*g*), the particle would have to be rendered as well, otherwise there would be a hole in the background object.

This is one of those problems inherent in the current architecture of BrushWave, and there are more. A solution would be to find a way to get rid of the reference picture / first rendering. But that would take away the flexibility … so I am currently quite at a loss of how to enhance the image quality of BrushWave in those cases.

On the project page, I am listing some tips to work around those problems for now.

I hope I could describe the dilemma so that it was understandable! Sorry that I cannot give you any better answers – your suggestions are really great and very much appreciated.

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