A liberal amount of blur addresses both issues: BlurĪfter feature generation, we’re left with something like this:Īside from the blocky artefacts from the downsampling, there’s also the problem of the ghosts maintaining the shape of the source image. While this could be applied during the upsample/composite step, fewer texture fetches are incurred by doing it as part of the feature generation step (depending on the downsample size and number of features). We can emulate this by sampling red, green and blue channels at different offsets: 5 )) float haloWeight = Window_Cubic ( d, uHaloRadius, uHaloThickness ) // cubic window function haloVec *= uHaloRadius Ĭhromatic aberration is another optical artefact, caused by varying indices of refraction for different wavelengths of light within the lens. x *= uAspectRatio vec2 wuv = ( _uv - vec2 ( 0. x /= uAspectRatio haloVec = normalize ( haloVec ) haloVec. We can use this to produce a ‘halo’ feature, weighting the samples to restrict the effect to a ring:īy default the aspect ratio will match that of the scene image, however it is possible to correct for this in order to achieve a more (or less) circular halo: vec2 haloVec = vec2 ( 0. This can be applied globally or per-sample:Ī different effect can be achieved by taking a vector to the center of the image (as for the ghost sampling) but fixing the vector length.
Smartshow 3d lens flare code#
We can also modulate the color of the samples according to a texture gradient, sampled based on the distance to the image center ( d in the code above).
![smartshow 3d lens flare smartshow 3d lens flare](https://cdn1.epicgames.com/ue/product/Featured/SunFlares_featured-894x488-a4e8641b5585a0feda0c5b432312e4a8.png)
The samples are weighted to fade out ghosts for bright spots near the edge of the source image. 5 ) - uv ) * uGhostSpacing for ( int i = 0 i < uGhostCount ++ i )
![smartshow 3d lens flare smartshow 3d lens flare](https://www.ephotozine.com/articles/smartshow-3d-slideshow-software-review--34097/images/highres-smartshow_1571057383.jpg)
0 ) - vUv // flip the texture coordinates vec3 ret = vec3 ( 0. The number of samples and sample spacing can be exposed as external controls. These can be generated by sampling along a vector which passes through the image center: ‘Ghosts’ are repeating blobs which mirror bright spots in the source image. This is easier to emulate with a sprite-based lens flare, but for the screen space technique we are restricted to sampling the source image in novel ways. In a real flare, the shapes of the features are determined by a combination of the lens and aperture geometry. Bright areas in the source image should project to other parts of the image along a path through the image center. Here we read the downsampled scene image in order to generate lens the flare ‘features’. A nice middle ground might be to use a small Gaussian blur instead of a box filter during the downsampling. Choosing the downsampled size is a tradeoff: smaller render targets make the feature generation and blur steps cheaper, however you may need more blur to hide blocky artefacts if the resolution is too low. Very likely you’ll have already generated a downsampled version of the scene image as an input to other post processing effects (e.g. This is very straightforward so I won’t describe it in detail.
![smartshow 3d lens flare smartshow 3d lens flare](https://bizweb.dktcdn.net/100/251/765/products/prospace-55-n-series.png)
The screen space technique comprises the following 4 steps: If instead we use the rendered scene image to directly drive the lens flare effect, any bright area can cause a flare and occlusion is handled implicitly. The downside of this technique is that it requires explicit placement of lens flares, as well as generating correct occlusion data to prevent the flare shining through foreground objects. The ‘traditional’ approach to simulating lens flares is to draw sprites along a path from the light source through the image center, using some occlusion data at the light source to decide how bright the overall effect is.
![smartshow 3d lens flare smartshow 3d lens flare](https://i.ytimg.com/vi/LA5na7ZT7wY/maxresdefault.jpg)
Along with other effects such as bloom, lens flares also increases perceived brightness, which is useful given the relatively low dynamic range of display devices. As with other photographic artefacts, it is desirable to emulate in games or CGI in order to create a ‘cinematic’ effect, enhancing realism by introducing the flaws found in real-world cameras. Lens flare is a photographic artefact caused by unintended reflections within the lens system (3). There is a sample implementation where you can refer to the final shader code. This post will be a more up-to-date and terse overview of the technique along with a couple of improvements to the compositing step. I had first read about this idea on Matt Pettineo’s blog (1), but the basic technique dates back to a GDC2003 presentation given by Masaki Kawase (2). A few years ago I wrote a blog post describing a screen space process for rendering lens flares.