Settings and Macros/ExponentialGlow Description
From VFXPedia
[ Main Manual Page ]
- Other macro tools in this category:
- [DepthDefocus]
- [DirectionalBlurFromPathGamma]
- [EllipticalBlur]
- [MotionVectorsCorrection]
| ExponentialGlow_v01 | Download |
This macro creates a photorealistic glow with an exponential falloff.
Development History and Discussion on PigsFly
A glow is just a blur that is added on top of the input image. Fusion's Glow and SoftGlow tools basically work like that and the result usually doesn't look convincing for strong glows (or in linear color space) so you need to create several blurs and glows with different radii to create a nicer-looking falloff. One technique is to add up blurs with radii that increase exponentially: 1, 2, 4, 8, 16 and so on. This macro does all the hard work for you.
This macro is based on a tool I found that was attributed to one Stuart Lashley. It's also similar to the great Multistep Blur (you would need to set it to a tiny minimum blur and a huge maximum blur with a high bias value to create a similar look). Also, this macro supports DoD and has been optimized to prevent unnecessary re-rendering when gain or tint are adjusted.
Main Inputs
The following inputs appear on the tool's tile in the Flow Editor:
- Input
- Source image. Required.
- Glow Mask
- A mask that defines the area that will glow (needs to be used instead of the blue effect mask like in Fusion's other glow tools). Optional.
Controls Tab
A straightforward multiplication factor for the blurred image before it gets added to the input image. ExponentialGlow is meant to mimic physical behavior so there are two things you should do first to make an object glow more: increase this gain slider or make an object actually brighter. In the example image above, the pink letters have a brightness that exceeds 1.0 to make them look as bright and glowy as the white letters.
Increases the radius of the glow. Be aware that ExponentialGlow will internally blur the image with 9 different radii. The smallest one corresponds to the value of this radius slider and is measured like Fusion's glow and blur tools. The largest radius will be 256 (2^8) and will reach across the entire image. This means that increasing the radius will not change the result much. Use this slider, however, to make the glow more narrow in case you don't want it to affect the whole image as much.
Defines the strength of the largest blur radii in the glow. Values smaller than 1 can be used to make the glow appear wider but will create a blown out image pretty quickly. Values larger than 1 will make the glow more narrow.
Control the saturation of the blurred image before it gets added to the input image. If you want to tint the glow in a color that differs a lot from the original hue, desaturating it first will help.
RGB multiplication factors for the glow, like the color scale sliders of Fusion's SoftGlow tool. This macro will not affect the input image's alpha or auxiliary channels.
Enabling this option will output the blurred images on top of a black image instead of the input image. Use this option if you want to do further processing to the glow like chromatic aberrations or anamorphic distortion.
This works like the blend slider in any Fusion tool. It's a useful way of fading the glow while still keeping the gain slider as a means to control its strength.
Advanced Tab
Since this tool is meant for a linear workflow, it will glow values > 1 with a soft shoulder all the way down to zero. This means that all parts of an image will receive the effect of a glow, as in reality light from every object scatters into the lens. If you feel that non-glowing objects appear too misty you can exclude their brightness by adjusting the low threshold value. A more realistic approach would be to decrease the glow's gain until the effect on non-glowing objects is no longer noticeable, then increase the brightness of surfaces that are actually self-illuminated until their glow is once again appropriate. The value of actual lights in a floating-point film scan usually go way above 1.0 which should be kept in mind for realistic CGI shots.
The largest blur radius is almost half the image size which will create a huge DoD that is usually a waste of memory. This slider limits the area of the DoD. Since it's usually good to have a bit of overscan for your glow when applying transformations to the glowed image afterwards, this slider defaults to 10%.
--Tilt
