This page provides information on the V-Ray Physical Camera parameters that can be added to standard Houdini cameras.
Page Contents
Overview
The V-Ray Physical Camera allows you to use real-world parameters to set up the virtual CG camera (e.g. f-stop, lens focal length, etc). This gives you access to lens properties such as aperture (F-Stop) and shutter speed as well as depth of field, motion blur, and more.
V-Ray Physical Camera also makes it easier to use light sources with real-world illumination such as V-Ray Lights with physical units or V-Ray Sun.
To add V-Ray Physical Camera parameters to a standard Houdini camera, use the Physical Camera button on the V-Ray Shelf. This will add a new tab to the selected Camera's parameters.
UI Path: ||Select camera|| > V-Ray Shelf > Physical Camera button
Main
Enable – Enables the V-Ray Physical Camera parameters.
Camera Type – Determines the type of the physical camera to simulate. This mostly has an effect on the motion blur effect produced by the camera:
Still – Simulates a still photo camera with a regular shutter.
Cinematic – Simulates a motion-picture camera with a circular shutter.
Video – Simulates a shutter-less video camera with a CCD matrix.
Specify FOV – Specifies the source for the camera's field of view setting. When enabled, the FOV parameter is manually set. When disabled, FOV is determined by the Focal Length parameter.
FOV – A value for the camera's field of view when Specify FOV is enabled.
Film Width – Specifies the horizontal size of the film gate in millimeters. Note that this setting takes into account the system units configuration to produce the correct result.
Focal Length – Specifies the equivalent focal length of the camera lens. This setting takes into account the system units configuration to produce the correct result. Vertical film gate size is calculated by taking image aspect ratio into account (vertical film size = horizontal film size / aspect ratio).
Zoom – Specifies a zoom factor. Values greater than 1.0 zoom into the image; values smaller than 1.0 zoom out. This is similar to a blow-up rendering of the image. For more information, see the Zoom Factor example below.
Exposure – When this option is enabled, the F-Number, Shutter Speed, and ISO settings affect the image brightness.
F-Number – Determines the width of the camera aperture. For more information, see the Exposure Control: F-Stop (f-number) example below.
ISO – Determines the film power (i.e. sensitivity). Smaller values make the image darker, while larger values make it brighter. For more information, see the Exposure Control: Film Speed (ISO) example below.
Shutter Speed – The shutter speed, in inverse seconds, for the still photographic camera. For example, a shutter speed of 1/30 of a second corresponds to a value of 30 for this parameter. For more information, see the Exposure Control: Shutter Speed example below.
White Balance – A color that can be used to alter the image output. Objects in the scene that have the specified color will appear white in the image. Note that only the color hue is taken into consideration; the brightness of the color is ignored. For more information, see the White Balance example below.
Use Vignetting – Enables the optical vignetting effect and Vignetting parameter.
Vignetting – Simulates the optical vignetting effect of real-world cameras. A value of 0.0 is no vignetting. A value of 1.0 is normal vignetting. For more information, see the Vignetting example below.
Optical Vignetting – Controls the strength of the optical vignetting, also known as "cat's eye" vignetting. This effect is due to the fact that the shape of the bokeh highlights resembles the shape of the aperture. As the distance to the optical axis increases, the bokeh highlights are progressively narrowed and begin to resemble the shape of a cat's eye. The larger the distance from the image center, the narrower the cat's eye becomes. Optical vignetting tends to be stronger in wide angle lenses and large aperture lenses, but the effect can be noticed with most photographic lenses.
Auto Lens Shift – When enabled, automatically sets the Lens Shift parameter to achieve 2-point perspective.
Horizontal/Vertical Lens Shift – Values other than 0 tilt the lenses to simulate 2-point perspective.
Lens File – Specifies the file for calculating the camera distortion when the Distortion Type is set to Lens File.
Horizontal/Vertical Offset – Shutter offset (in degrees) for the cinematic camera.
Subdivs – Specifies local subdivisions for the camera, which control the number of paths traced from the camera.
Motion Blur – Turns on motion blur sampling. For more information, see the Motion Blur (MB) example below.
Thin Lens Equation –
The following parameters of the physical camera are linked to some of Houdini's channels as part of the integration of V-Ray for Houdini:
- Film Width is linked to Aperture
- Focal Length is linked to Focal Length
- F-Number is linked to F-Stop
- Horizontal/Vertical Offset are linked to Screen Window X/Y
Distortion
Enable – Enables distortion sampling for the V-Ray Physical Camera.
Distortion Type – Determines what formula is used to calculate the distortion for the camera
Quadratic – This is the default distortion type. It uses a simplified formula that is easier to calculate than the Cubic method.
Cubic – This is the distortion type used in some camera tracking programs like SynthEyes and Boujou. If you plan on using one of these programs, use this distortion type.
Lens file – An external .lens file is used to determine the distortion for the camera.
Texture – A displacement map from third party application (i.e. Nuke) can be used to determine the camera distortion.
Distortion – Specifies the distortion coefficient for the camera lens. A value of 0.0 means no distortion; positive values produce "barrel" distortion, while negative values produce "pillow" distortion. This parameter has an effect only when Quadratic or Cubic is selected as the Distortion Type. For more information, see the Distortion example below.
Distortion Texture – The texture to be used to determine the camera distortion when Distortion Type is set to Texture.
Depth of Field
Enable – Turns on depth of field sampling. For more information, see the Depth Of Field (DOF) example below.
Focus Distance – Sets the focus distance of the camera.
Threshold – Specifies the display threshold for the Depth of Field (DOF) effect.
Bokeh Enable – When enabled, simulates a polygonal aperture.
Number of Blades – Specifies the number of blades of the polygonal aperture.
Blades Rotation – Defines the rotation of the blades in radians.
Center Bias – Defines a bias shape for the bokeh effects. Positive values make the outer edge of the bokeh effects brighter; negative values make the center of the effect brighter.
Bokeh Anisotropy – Allows stretching of the bokeh effect horizontally or vertically to simulate anamorphic lenses. Values other than 0.0 stretch the bokeh effect horizontally or vertically.
Bitmap Aperture
Enable – Enables a texture file to define the shape of the aperture.
Exposure – When enabled, the texture will affect the camera's exposure in addition to the shape of the aperture.
Texture – Specifies the texture file that will determine the shape of the aperture.
Resolution – Specifies the resolution of the texture file.
Example: Zoom Factor
The Zoom Factor parameter determines the level of zooming (in and out) of the final image. It does not move the camera forward or backward.
Settings for example images:
Exposure: on
F-Number: 8.0
Shutter Speed: 60.0
ISO: 200.0
Vignetting: 1
White Balance: white
Zoom Factor: 1.0
Zoom Factor: 2.0
Zoom Factor: 0.5
Example: Distortion
Distortion: 1.0
Distortion: -1.0
Example: Exposure Control: F-Stop (F-Number)
Lowering the F-Number value will actually make the image brighter. Thus, the camera aperture is being opened, so more light is absorbed.
In reverse, increasing the F-Number will make the image darker, as the aperture is being closed. This parameter also determines the amount of the DOF effect.
Settings for example images:
Exposure: on
Shutter Speed: 150.0
ISO: 100
Vignetting: 1
White Balance: white
Lights: VRaySun and VRaySky with default parameters
Note: The Sponza Atrium model was created by Marko Dabrovic ( http://www.rna.hr/ ) and was one of the models for the CGTechniques Radiosity competition .
F-Number: 8
F-Number: 6
F-Number: 4
Example: Exposure Control: Shutter Speed
The Shutter Speed parameter determines the "exposure time", or how fast the shutter opens and closes. A lower value means the shutter is "slow", so the shutter is open longer, letting in more light and making the image brighter. Conversely, a high Shutter Speed means the shutter is open for less time, letting in less light and making the image darker.
This parameter also affects the Motion blur effect (see Example).
Settings for example images:
Exposure: on
F-Number: 8.0
ISO: 200
Vignetting: 1
White Balance: white
Shutter Speed: 200
Shutter Speed: 100
Shutter Speed: 400
Example: Exposure Control: Film Speed (ISO)
The ISO parameter determines the sensitivity of the virtual "film" in the camera. If the film speed (ISO) is high (more sensitive to light), the camera requires less light to get the image. Higher values are usually used for "night shot" images.
Settings for example images:
Exposure: on
F-Number: 8.0
Shutter Speed: 400.0
Vignetting: 1
White Balance: white
ISO: 400
ISO: 800
ISO: 1600
Example: White Balance
Using the white balance color allows additional modification of the image output. Objects in the scene that have the specified color will appear white in the image. As an example, for daylight scenes the color can be set to peach to compensate for the color of sunlight.
Settings for example images:
Exposure: on
Shutter Speed: 200.0
ISO: 200
Vignetting: 1
F-Number: 8.0
White Balance: White (255,255,255)
White Balance: Blue (171,244,255)
White Balance: Peach (255,223,182)
Example: Vignetting
Vignetting: 0
Vignetting: 1
Example: Depth Of Field (DOF)
To create a depth-of-field effect in the render, enable the Use DOF option. Blades settings (Bokeh effect) are also part of the DOF effect.
The effect is strongly seen when the camera is very close to some object, as with a macro photo. To have a strong DOF effect, the camera aperture has to be "wide open" which equates to a small F-Stop value. That would lead to a very burnt/bright image, so to preserve the same luminosity over the whole image, the shutter speed has to be quick. And at last but not at least, the focus distance determines which part of the field will be actually be in focus.
Settings for example images:
Shutter Speed: 4000.0
ISO: 30
Vignetting: 1
F-Number: 1.0
Use DOF disabled
Use DOF enabled, Focus Distance: 80
Use DOF enabled, Focus Distance: 140
Example: Motion Blur (MB)
In order for motion blur to appear in the rendering, the Use Motion Blur option must be enabled.
The size/amount of the motion blur is determined by the speed of the moving object itself as well as the Shutter Speed of the camera. Low shutter speeds will produce more motion blur, as the shutter is open longer and the camera sees the movement of the object longer in time.
Keep in mind that lowering the shutter speed also brightens the image; to compensate for greater or lesser light due to changes to the Shutter Speed, change the F-Number value in the opposite direction (higher or lower).
Settings for example images:
Exposure: on
ISO: 8
Vignetting: 1
Motion Blur disabled
Motion Blur enabled, F-Number: 16.0, Shutter Speed: 4
Motion Blur enabled, F-Number: 8.0, Shutter Speed: 16