Glare

Category: mental ray > Output

Shader Family: Output

Output: Color

Bright lighting in CG images is often difficult to accomplish. Many times bright areas appear as solid white splotches with unrealistically hard edges. Glare comes to the rescue in these situations by giving a halo around extra bright areas.

In particular, Glare is extremely helpful when an image has areas of "over-exposure." Over-exposure occurs when color values move beyond the solid white value of 1. While the color white (R:1.0, G:1.0, B:1.0) may look the same as the color extra-bright-white (R:2.0, G:2.0, B:2.0), Glare treats them differently, giving larger halos to brighter objects.

It should be noted that Glare gives realistic glares and flares from any bright source - not just lights. For example, it will create glares off of shiny metals, flares from reflections on a water surface or glass object, etc.

Name	The name of the shader node displayed in the render tree. Enter any name you like, or leave the default.
Quality	Sets the trade-off between detail and speed. Glare can begin to slow down rendering times when the scene has large bright areas. Lower Quality settings will cause Glare to run more quickly, but may cause the glare halo to be "boxy," whereas Higher Quality will give a better overall effect, but will of course take longer. Generally, a mid-level setting is appropriate for most scenes.
Spread	Controls how sensitive Glare is to bright objects. Lower values for Spread will cause smaller glare halos while higher values will cause larger glare halos. Very high values will cause dark objects to have halos. (Try not to abuse the Spread parameter. The best way to increase an object's halo is to increase its brightness, not to increase the Spread.)
Overlay Only	Produces a glare "overlay". The overlay is an image of the glare effect only; the original underlying image is removed. This mode is useful when render speed is critical, so that Glare can be run on a lower resolution image to produce an overlay, which can then be composited with a higher resolution underlying image.
Verbose	Turns on verbose output, so that the progress of Glare can be monitored.
Streaks	When on, you can specify an image file that will be used to create a streaking effect, as seen when looking at bright images through glass or, in photographs, through a camera lens.
Streaks Image	The streak image template that Glare uses to draw streaks.
Scale	Controls how big the streaks image should be. A value of 1 means that one pixel in the streaks image should cover one pixel in the output image. Smaller values will make the streaks image smaller, larger values make the streaks image larger.
Contrast	Controls the variation in brightness between the streaks and the darker region between the streaks. A value of 0 causes the streaks and dark regions to have the same brightness; a value of 1 causes the streaks to have the maximum brightness and the dark regions to be black.
Specific Objects	By default, all of the image is affected. Enabling Specific Objects causes the effect to apply to only those pixels whose tag matches the values in the Object Labels list. The label image and any user defined framebuffers of type TAG (object label) are used by the selection process.

Object Labels

Creates a object labels list to specify which objects will receive the effect.

Add	Adds a object label Item to the list.
Clear	Removes all object label Items from the list.
Item	An Item port (parameter) representing a single object label in the list. Enter a value for the object label.
	Click the Edit Item icon to Remove, Rename, Move Up, and Move Down each Item entry in the list. Once an Item is removed from the list, it no longer influences the effect created by the shader. In most cases, the position of an Item in the list indicates its order of evalution. Changing the evaluation order (moving Items up and down in the list) can impact the final output results of the shader.

Specific Objects Buffer	Specify the name of a user-defined framebuffer to be used to output the label image.
Calculation Resolution	Specify the output resolution to be used by the framebuffer.

Render Tree Usage

This output shader is applied using a pass shaders stack. For more information, see Applying Shaders to Partitions [Rendering].

Except where otherwise noted, this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License