APP/APG v2.0 Render Settings
The Render dialog will allow you to set the panorama rendering parameters.
There are 3 ways to choose the output size of the panorama:
- With the slider (percent of the max. size)
- By entering a numerical value for the desired width (value expressed in pixels)
- By entering a numerical value for the desired height (value expressed in pixels)
The panorama’s maximum size is given on the first line (taking into account any use of the Crop tool). This maximum size (100%) is the resulting size of the source images after stitching. At the maximum size, all the details recorded when shooting the scene will be restituted in the final image.
Notes: don’t feel pressured to always use 100%. When working with a Planar Projection or Cylindrical Projection with a FOV wider than 90°, the pixels located in some specific areas of the resulting image will abnormally be stretched (right and left edges in Planar, top with Cylindrical). If we choose 100% the image sharpness cannot be constant across the resulting image, it can be a good idea to take this fact into account and reduce the value to 70% or even 50%. As far as the time needed to render the final image, surface determines the computing load: going from 100% to 30% will give you a 1 to 10 increase in rendering time!
Maximum size with multiple focal lengths: when working with a panorama using source images shot at various focal lengths, the maximum size of the resulting image is calculated based on the source image with the highest amount of details (i.e the longest focal length) and this image is given a ratio of 1 (i.e. for one pixel of this image, there will be one pixel in the final panorama). Therefore, the pixels belonging to the source images taken with shorter focal lengths will be stretched in the rendering process.
The Blender and Interpolator are two algorithms used to manage the global output quality of the panorama.
The interpolator is used to reproject the source image’s pixels on the panorama. The Interpolator’s quality will then influence the sharpness of the rendered panorama.
- Nearest neighbor: to be used for testing purposes only because of the large amount of artifacts it produces. As a tradeoff it’s the fastest of all.
- Bilinear: represents a decent quality/speed ratio.
- Bicubic: if you don’t know which one to pick this is the one you should be using. Any differences from Bilinear will be hardly visible to the naked eye, but can be seen on highly contrasted lines. It is the default recommended setting.
- Bicubic Sharper: same formula as Bicubic with some strength added (same as bicubic, only a touch stronger). This sampling mode is the same as the one found in the "Image Size" dialog, in the "Resample Image" drop-down of Adobe Photoshop.
- Bicubic smoother: same formula as Bicubic with less strength (same as bicubic only a touch lighter). This sampling mode is the same as the one found in the "Image Size" dialog, in the "Resample Image" drop-down of Adobe Photoshop.
- Spline36: the use of this powerful interpolator is to be reserved for cases where heavy post-processing will take place. To the naked eye, there is absolutely no visible difference with Bicubic.
- Spline64: more powerful, slower but generally even better than Spline36 (if you can “see” the difference!). Same as for the Spline36 interpolator: to be reserved for cases where heavy post-processing, including reprojection and successive image transformations will take place.
The Blender is an algorithm used to combine several reprojected images (source images projections on the panorama). The Blender is generally used on the areas where the sources images overlap, but not only. There can be cases where it will modify some pixels outside of the overlapping areas (i.e. where only one input source of pixel is available). Le primary goal of the Blender is to combine the source images (two, sometimes more) and process the overlapping areas to produce a seamless panorama.
Several blending algorithms are available:
- None: no blending is performed; the "top picture" is used. The stitching seams are obviously visible (geometry and/or brightness).
- Linear: : this mode is very fast and can be a good compromise between quality and speed if you are not too demanding on quality.
- Multiband: this slower mode will produce much better results than the "Linear" mode. The transitional areas between images will hardly visible. However this mode does not take into account objects that could have moved from one shot to another and some “ghosting” can occur.
- Smartblend: this blender combines a Multiband blender and picture analysis engine in order to identify common objects present in the source images (a moving object, a strong line,…). Based on the results of this analysis, Smartblend tries to keep the features common between images (edges, lines, curves,…) and automatically discard objects that have moved between shots. Even though much slower than the other algorithms, this blender produces a much higher rendering quality.
Be aware: this blender is not HDR compatible yet.
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Layers: None / Embedded / File
When performing a rendering with Autopana Pro, it is sometime useful to reproject the totality of the surface of the stitched source images to, in a second time, edit the resulting panorama with an image processing software.
This can be done with all available file formats, except that some file formats will support embedded layers within a single file (PSD/PSB) and some won’t. Three options are provided to manage embedded layers:
- None: none of the reprojected source image will be kept.
- Embedded: this option will be enabled if supported by the selected file format. In this case each individual source image will be added to the rendered file as an separate layer.
- File: each individual source image will be rendered in a separate file; you will obtain one file per image.
The color and brightness corrections applied to the panorama are also applied to the individual layers: Color Correction, Filters and Levels are applied.
In the other hand the Blender is not active on the source images; therefore it has no effect on the resulting individual layers. This, even if surprising in the first place, is absolutely necessary. This will translate into color and brightness variations between the different layers themselves, and also between the layers and the background layer (the resulting stitched panorama is assigned to the background layer in Photoshop).
The layers will be arranged correctly, barrel and pincushion distortions are corrected.
For the JPEG, TIFF and PSD/PSB file formats, Autopano Pro will store the original Exif data (found in the source images) into the rendered file. This allow for tracing the original shooting conditions. It also adds some improvements:
- ImageDescription (0x010E): "Stitched Panorama"
- SoftwareUsed (0x0131): "Autopano Pro"
- FileChangeDateTime (0x0132): the panorama’s rendering date
- UserComments (0x9286): A short summary for describing the panorama, as it appears in the Panorama Window.
Notes: at the present time, no calculation is being made to compute the equivalent focal length of the panorama. We focused more on keeping the original shooting condition rather than producing numerical values for the resulting panorama.
This area of the dialog will allow you to choose a path and a filename for the resulting panorama.
- Path: Easy! This is the file folder where the resulting file will be stored.
- Filename: Well… it becomes a little more complicated but very powerful. Instead of giving always the same filename we came up with a system that generates the file name using a powerful syntax. This system will allow you, for example, to specify the height * width, the interpolator or blender used, etc. inside the produced filename. The syntax is as follow:
|%i / %I||Short/long name of the first image of the panorama|
|%j / %J||Short/long name of the last image of the panorama|
|%n||Number of source images|
|%s||Render size (Ex: 11,254 x 2,541)|
|%f||FOV (Ex: 25.6° x 14.3°)|
|%p / %P||
Short/long name of projection mode used
|%t / %T||
Short/long name of the interpolator used
|%b / %B||
Short/long name of the Blender used
|%c / %C||
Short/long name of the color correction applied
|%l / %L||Group name as defined in the Layer Editor|
|%v||Version of Autopano Pro used for rendering|
|%g||Panorama # (unique global index #)|
The following model is used by default: "Pano - %i - %s - %p%t%c - %l" returning the following:
"Pano - DSCN0839 - 1261x512 - SLIN - Blended Layer.psd"
Name of the first image: DSCN0839 Render size: 1261x512 SLIN => (S)pherical, (LI)near, (N) no color correction
- Name: this area of the dialog displays a translation of the naming syntax model used, allowing you to preview the final filename. It also displays real time information regarding possible naming conflicts: does this name already exist? We wouldn’t want to overwrite an existing file.
Note: a panorama can generate several files if you created some layers using the Layer Editor. They will all be listed here. In the same way, if one of the file to be rendered contains embedded layers a small crosshair will appear next to its name. You can click on this crosshair; a list of all the layers that will be created during the rendering process will then be displayed.
- Overwrite existing files: this option allow you to force file overwrite.
- Add an ending number in filename to prevent overwrite: this option will automatically modify the filename by adding a trailing series of numbers to the filename in order to avoid conflicts.
- Render: apply the chosen parameters, launch the rendering and close the dialog.
- Apply: apply the chosen parameters, close the dialog, but does not launch the rendering.
- Cancel: cancel all changes and close the dialog.
About our Rendering Engine
During the rendering operation,as you may have noticed, everything is performed on small cells; this is a technique called "cell-rendering". The whole workload to be performed on the panorama is divided in a set of small jobs, taking in charge small portions of the final image. This model is a lot harder to develop but presents huge advantages:
- Immediate support for multi-core / multi-processors systems: each computing unit manages a cell (in the future, this same approach will be used to easily perform network rendering and split the work load across multiple computers on a network).
- The amount of RAM required is lower: this is a logical consequence as we reduce the amount of work to be performed to a small cell, we then need less resources to process it (the number of source images used in a cell is often reduced to a maximum of 3 or 4 images, even if the panorama is composed of a 100 source images).
VFW, virtual file writer
This exclusive technology combined with cell-rendering allows us to even further reduce the resources needed to generate very large panoramas. You will be able to generate panoramas from a large number of source images even if your computer does not have a lot of RAM.
For example, if you perform a rendering from jpeg source images using Multiband as blender and writing to a PSD file, the Virtual File Writer will generate the panorama without the need to create a temporary file or using a lot of RAM. Everything is perfectly optimized for this mode to be as efficient as possible, even with panoramas of several gigapixels.