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WShawn
04-12-2004, 12:09 PM
Hello:

I'm building a candelabra for a client. It has 20 arms with a candle on each arm, and they want each candle to have a sort of stylized glowing lens flare sort of thing, not a realistic flame (I need to put photos of people in some of the glows).

My plan was to render a stylized lens flare/glow element in After Effects and then apply that as a clip to hypervoxel sprites located at the tip of each candle wick. That way the glow/flare would always appear to face the camera. Unfortunately, when I do this, the image is being shifted within the sprite so that the glow is not centered on the wick; it gets offset to the side.

I'm having problems attaching an image, so here's a link:

http://homepage.mac.com/wshawn/SpriteClip

The first frame shows a sprite with no clip, and it is centered over the wick. But when I add a clip it appears offset within the sprite so that the flare appears to be hovering next to the wick instead of centered on the wick. The frames showing the concentric circles show how the image is being shifted and cropped, and the extent and angle of the shifting changes with the camera's orientation to the sprite.

Is this just the way things work with sprites? Does it have to do with the way sprites use "slices" of things.

As a workaround I tried putting a little point light on the wick and rendered the lens flare within LW, but this isn't ideal since lens flares don't grow as they get closer to the camera. I'll probably end up mapping the image to polygons and have them always point to the camera.

LW 7.5c, Mac OS 10.2.6.

Thanks.

Shawn Marshall
Marshall Arts Motion Graphics

mkiii
04-12-2004, 05:31 PM
I really don't know what causes this - I've checked it out on my setup, and the same offset happens. It happens at random points around the edge too, and I can't see why it does that.

You could redo your clip maps to include a blank border around the edge to try & keep the image complete, but it will still be offset.

One question - what are you using to attach the HV sprite(s) to?Are you using particle emitters, Nulls, or som other method?

I did notice that the offset problem occurs when I attach to any particle type, but does *not* happen when I use a null as the active object.

WShawn
04-12-2004, 06:31 PM
Hi:

Thanks for confirming that you get similar results. I do have a fair amount of black space around my flare image, so the cropping isn't evident; the problem is that it's not being centered over the wick, making it look like the flares are floating in mid-air.

In the examples I've shown I am applying the hypervoxel to a null object, so I'm not sure why that works for you. I initially laid out the 20 points I wanted to use in modeler and added hypervoxels to that object in layout. When I saw the offset problem I thought I wasn't doing something right so I tried to manually position nulls on top of the wicks in layout, but that doesn't seem to work for me either.

Wacky.

Shawn Marshall
Marshall Arts Motion Graphics

mkiii
04-12-2004, 07:01 PM
Ahh... I just noticed why *my* null had no offset visible. It was at the origin. When I moved the null to one side or the other, there was a noticable offset on the side furthest away from 0,0,0

This with a camera pointing at the origin.

After further investigation (call me Sherlock), I notice that the sprite offset is in relation to centre of the camera view, not the axis - so moving the sprite to one side = clip offset. rotate camera so the sprite is centred again, and the clip offset vanishes.

I can find no way of getting rid of it. Sorry.