List of Image Effects
Blur
The blur effect smoothes the image by blending adjacent pixels. This produces a smoother image and sometimes can be used to anti-aliase the image. For example texture flickering of insufficiently anti-aliased animations can be reduced this way.
The Blur effect can be controlled using the following settings:
- Blur Level: Defines the amount of blur. Increasing the value makes images more blurred.
- Blurred Channel: The image channel to be blurred. Usually the color channel is the most suitable target.
- Threshold Channel: An optional channel that can be used for selective blurring. The user can add a channel property to part of scene objects and then apply blur to only those parts of the image where the channel values is above the given limit value (i.e. defined objects are visible).
- Threshold: The threshold value that triggers blurring.
Depth of Field
The depth of field effect simulates image blurring of photographs. Cameras (except the pinhole camera) use a certain aperture for exposing the image to the film. Therefore, rays coming from different parts of the scene can expose the same point on the film. The greater the aperture, the more blur the photograph will contain.
The effect has the following controls:
- 'Camera defined': If set, the amount of depth of field blur is defined by the settings of the current camera (focal length, F-stop, focusing distance). Experienced photographers can estimate the amount of blur from the camera properties. Other users may find it more suitable to clear this option and use the other settings listed below to directly control the effect.
- 'Blur strength': Defines the maximum amount of blur when 'Camera defined' is off.
- 'Blur sensitivity': Defines how quickly the maximal amount of blur is achieved away from the sharp distance. Used only if 'Camera defined' is off.
- 'Sharp distance': The distance from the camera where the image is totally sharp (when 'Camera defined' is off).
Camera defined depth of field for view rendering
1. Go to the 'Post Image Effects' tab. Drag and drop the post image you find suitable to the view window (for example 'Default Effects').
2. Open the property window to see the properties of the above mentioned post image. Make sure that a 'depth of field' object is included in the active effects. If not, add one to the active effects (you may first have to create a depth of field effect using the 'New' popup menu of the select window). Select the depth of field effect and verify from the property window that 'Camera defined' is set.
3. Open the view property window. Go to the 'Camera' tab and set the 'Depth of Field' option. Close the window and render the view. You can adjust the amount of blur from the 'F-Stop' gadget of the view property window. The smaller the value, the more blur. Typical real world F-stop values range from 1.8 to 22.
The selected post effect configuration includes 'Camera defined' depth of field and the view has 'Depth of field' enabled
Camera defined depth of field for file rendering
1. Go to the 'Post Image Effects' tab. Select the post image you plan to use for file rendering (for example 'Default Effects'). Open the property window to see the properties of the post image. Make sure that a 'depth of field' object is included in the 'Active Effects'. If not, add one to the active effects. Select the depth of field effect and verify from the property window that 'Camera defined' is set.
2. Go to the 'Geometric Objects' tab of the select window. Make sure that there is a camera object included in the scene. If not, create one using the camera tool. Select the current camera object from the hierarchy (or all of them in case you are using multiple cameras for animation). Go to the 'Camera' tab of the property window and set the 'Depth of Field' option. Close the property window.
3. Open the file rendering window. Prepare settings as usual, but remember to select the post processing configuration which includes the depth of field effect. Render as usual.
The scene contains a camera, which has 'Depth of field' option set. File rendering uses a post processing configuration 'Default Effects', which includes a 'Camera defined' depth of field effect.
Custom depth of field for view rendering
1. Go to the 'Post Image Effects' tab. Drag and drop the post image you find suitable to the view window (for example 'Default Effects').
2. Open the property window to see the properties of the selected post image. Make sure that a 'depth of field' object is included in the 'Active Effects'. If not, add one to the active effects (create a new one using the 'New' popup menu of the select window if necessary). Select the depth of field effect and clear the 'Camera defined' option using the property window.
3. Render the view. Note that a strong depth of field effect may take a long time to render, so it may be a good idea to use 'Render/Define render box' menu of the view popup menu to render suitable test areas only. Adjust the 'Depth of Field' attributes from the property window and re-render (or post process only if backup buffer is enabled) until the result is suitable.
Note that you do not have to pay attention to the view property window's 'Depth of field' option in this case.
Custom depth of field for file rendering
1. Go to the 'Post Image Effects' tab. Select the post image you plan to use for file rendering (for example 'Default Effects'). Open the property window to see the properties of the post image. Make sure that a 'depth of field' object is included in the 'Active Effects'. If not, add one to the configuration. Select the depth of field effect and clear the 'Camera defined' option using the property window.
2. Open the file rendering window. Select the post processing configuration, which includes the depth of field effect prepared above, to the 'Image Effect' field.
3. Render as usual.
Dithering
This effect adds dithering to the image. Most commonly used image standards use a limited amount of colors to represent images. The human eye is very accurate in detecting differences between colors and therefore even 16 million colors is not always enough. Dithering improves image quality by blending available colors.
The effect has following controls:
'Red bits', 'Green bits', 'Blue bits': The suitable amount of dithering depends on the accuracy, which is used for storing the image. You can select the data type accuracy using these sliders. Value 8 is suitable for 24 bit output (16 million colors). Value 5 is suitable for 32 000 color output (16 bits).
'Channel': The effect can be used for dithering any channel. Color channel is the usual target of dithering, but you can select another channel from this list.
Note: View window has its own dithering mechanism and the ray tracer output can also be dithered before post processing starts (while the data is still in accurate floating point form). Therefore dithering post effect is seldom needed.
Edge Filter
The edge filter effect finds object silhouettes, edges and other areas where contents of the image change rapidly. The edge pixels are set black and other pixels white.
The controls of the effect are:
'Threshold Value' defines the amount of change between adjacent pixels which is required from edge pixels. The smaller the value, the more edges appear to the image rendered by the effect. A full value 1.0 usually generates an empty white image (when examining the color channel).
'Threshold Channel' selects the data channel, which is used for detecting edges. By default, color changes are examined. You can also use 'Distance' and 'Ray Normal' channels for detecting edges - or any other channel.
'Output Channel' defines to which channel the black and white result image is written. The default 'Color' channel overwrites the original shaded image. You can write the output to another channel and for example blend it with the shaded output using a VSL effect.
Fog
The Fog post processing effect provides a quick way to add global fog to the scene.
The fog controls are:
'Fog color': This is the color of the fog.
'Min Distance': Fog does not affect objects closer than this distance from the camera.
'Max Distance': The distance from the camera which is needed for full fog effect. If saturation is 100, objects further than this distance are fully obscured by the fog.
'Max Saturation': Defines how strongly the fog effect at its full level obscures objects. If the saturation is 100 %, the fog can fully hide objects. 50 % saturation blends maximally half of the fog color to the original image.
Glow
The 'Glow' effect is a part of the post effects 'Default Effects' configuration. It processes the image using two glow specific properties:- Glow Size and
- Glow Color
The glow effect examines the current scene and detects any use of the above mentioned channels. If they are not used, the effect is not executed. Therefore, you don't have to remove glow from the post processing configuration for speed reasons. You only have to remove it from the current post image in case the scene contains glow materials but you still want to disable glow rendering.
Glow effect
'Saturation' adjustment defines how quickly maximal glow brightness is reached in volume with respect to the distance. If the saturation value is zero, the glow looks brighter around the edges of the object - and has less intensity on the object itself, resulting in a kind of 'aura'. If the saturation is set to 1, an equally bright glow is generated in front of the glowing object as well as the edges.
Full saturation level on the left
and zero saturation on the right
The 'Accuracy' setting is an anti-aliasing type quality adjustment. The default value of 0.5 is suitable in most cases. The value range is from zero (fast, inaccurate) to 1.0 (slower but accurate).
Note: suitable glow size values are typically quite small, for example 0.01 (1 centimeter) is pretty good for default scale models. Large glow sizes like 1.0 may take a long time to render.
Note: When rendering an image with post effects to an animation, the rendering engine must expand the image internally. This increases rendering time significantly. If you only need to render one single still image of a scene containing many glowing objects, you can often increase rendering speed dramatically by switching 'Post Proc./Safety Area' and 'Distrib/Box Rendering' off from the render settings property window.
Image Flare
The image flare effect finds the brightest areas of the image and adds highlight flares to them. It uses the following principles:- Only places where a given threshold value is exceeded get a flare
- Only one flare is added per a continuously connected bright area
- The size of a flare depends on the brightness of the area generating it
Image flare properties
'Brightness Trigger' defines the threshold value, which must be exceeded before a flare appears. The value is defined as a sum of red, green and blue. A pure white color has brightness 3.0 and pure red has brightness 1.0, etc.
'Max Flare Count' defines the maximum number of flares added to the image. Only the defined amount of brightest areas will get the flare. This is the maximum amount, not the exact amount. If the picture is too dark, no flares will be added.
The lower part of the image flare properties window contains the standard lens flare gadget. See the description of the Lens Flare effect for details.
The effect can extract highlight areas better, if you change the channel data type of 'Color' of the parent post image from the default 'Byte' to 'Word' (see the Post Image description for details). A byte can only represent a brightness scale from black = 0 to white = 1, whereas 'Word' channels can store values from zero up to 16. In other words, there are plenty of brightness values after white, and the program can locate the maximum brightness spots better.
Note: Do not use box rendering with the image flare effect. Render boxes break continuous bright areas and flare computations become inconsistent between boxes.
Particle Effect
This post processing object is actually not a real 'effect' - it does not render anything itself. However, it does the important job of managing the rendering of all post particle effects. The position of this object in the post processing configuration defines when post particle drawing takes place.
The configuration on the left shows a situation, where post particle effects are drawn as the first step of post processing. The right side image shows a configuration, which draws post particles last. Note that in the latter configuration, post particles cannot have the glow property.
Saturation
This effect changes the color saturation of images. It has only one property 'Color Saturation'. The lower the saturation level, the less colorful the processed image becomes. Full saturation 1.0 leaves the image unchanged, whereas zero saturation turns it into a gray scale image.
Saturation level 1.0 on the left, saturation 0.5 on the right
Post Image
The Post Image object has an important role in all post processing configurations: it allocates the image buffer, which other post effects modify. It also acts as a parent effect, having a number of child effects, which modify the parent's image buffer.
A post processing configuration defined by a post image
A post image can be configured by adding a set of suitable effects to its 'Active Effects' list. The child effects can be added by drag & drop from the 'Available Objects' list or by using the popup menu of the same list. Effects can be removed from the 'Active Effects' list by selecting them and using the 'Remove' popup menu item. The child effects are rendered in the order they appear in the 'Active Effects' list - sometimes this has importance.
The 'Channels' tab of the post image property gadget contains a list of all installed channels. When you select a channel from the upper 'Channel' list, the 'Storage' field displays the data type, which is used for storing the channel values. 'Byte' takes the smallest amount of memory space but is inaccurate. 'Float' is the most memory hungry but very accurate. The most suitable data type depends on the channel - 'Byte' is usually enough for storing the color, but never accurate enough for the distance channel and cannot represent a wide enough value range. The default types are suitable for most cases, but sometimes using higher accuracy is necessary (see the image flare documentation for an example of this).
'Float' data type usually gives fastest rendering times, because it is the render engine's native way of representing channel data. Use of other data types leads to data type conversions. However, due to high memory consumption, it is seldom possible to use the float data type for all channels.
You do not have to define which channels to include in a post image. The post image can find out which channels are used by child effects. It includes them automatically.
Post images can be used hierarchically. Each effect must be added to a post image, then the post image can be added to another post image to obtain the hierarchy. Below is a simple hierarchical post image configuration:
Both 'Main image' and 'Post Image' are post image objects. The sub image 'Post Image' allocates a new image buffer and glow effect is rendered into it. The VSL effect does some custom manipulations after that. The final step is star filter effect rendering into the main image.
If 'Initialize All' option (see the channel tab image above) is set, the post image automatically reads the contents of all the channels being used by its child effects from the parent image. In other words, when the effect drawing of the sub post image starts, the situation is exactly the same as in the parent image. You can clear the 'Initialize All' option and define manually which channels should be initialized in the beginning. Other channels will have zero contents. You can add channels to the 'Initialize Selected' list by using the popup menu of the 'Channel' list gadget. Removing channels happens by using the popup menu of the 'Initialize Selected' gadget.
If 'Output All' option is set, all included channels are written to the parent image after sub effect rendering. To overrule this, clear the option and build a list of output channels to the 'Output Selected' list.
Sometimes it is useful to clear the 'Initialize All' option, but leave the initialization list empty. The effects will be drawn over a black background and the result can be, for example, added to the parent image. Anyway, it never makes sense to disable 'Output All' and leave the output list empty - rendering effects without outputting the result somewhere just wastes rendering time.
VSL Effect
The VSL Effect can be used for defining arbitrary pixel effects. Using the VSL shading language, the user can move data from a channel to another one, blend channels together, make color corrections, etc.
The 'Image Coordinate Channel' defines the channel, to which the effect writes the coordinates of the processed pixel. The pixel coordinates are in floating point form: the top left corner has the coordinates (0,0,0) and the bottom right corner is (1,1,0). Use of relative floating point coordinates guarantees that VSL effects are resolution independent. When rendering boxes, the pixel coordinates are scaled to the range, which the box covers of the total image. Therefore, you can safely use box rendering with this effect.
The default image coordinate channel is the 'UV coords' channel. In the example image above, a random noise is added to the rendered image. The amount of noise depends on the UV coords.
The lower part of the VSL effect's property window contains the standard VSL editor. By checking the 'Advanced' option, you get access to the editing tools. See the 'Materials' chapter of the manual for VSL programming instructions.
The VSL objects of the image processing tree 'see' all channels of the system and can freely perform any suitable computations using the channels. Because of the auto-configuration property of the post processing system, referring a channel from a VSL object automatically includes the channel in the post processing data flow.
