Presenter Lighting

Lighting Tab

Like the Materials Effects and Rendering tabs, the Lighting tab is divided into two panes - the archive on the left and the palette on the right. The archive contains individual lights, as well as light studios. A light studio is a combination of lights that work well together. The palette contains all the lights that are active in the scene.

To apply a light to the scene, you drag it from an archive into the palette, at which point you can edit its parameters if required. The light is added to those already in the scene.

To apply a light studio to the scene, you drag it from an archive into the palette. All the lights in the light studio replace those already in the scene. Light Studios are applied to the scene intelligently. The light studio is oriented and scaled to match the scene to which it is being applied. You can also expand a light studio in the archive and drag the lights into the palette individually. If you do this the lights are not oriented or scaled to match the scene.

Each light in the palette has a check box, which can be used to turn the light on or off in the scene.

The following sections will describe how to manage and edit lights for insertion into the scene.

Adding And Positioning Lights

Lights and light studios can be taken directly from the archives and applied to the scene by simply dropping them into the palette. These can then be repositioned as you wish.

The Recommended archive contains five lights (Ambient, Distant, Eye, Point and Spot ), a Standard Light Studio , an Environment Light Studio , an Environment folder containing two Environment lights utilising HDRI-based light sources (see for more information), and an Exterior folder, that contains three light studios for different city locations around the World (Clear Sky, Overcast Sky and Sun Study

If you are creating an external render of a building, for example, then you may find that one of the Environment light studios can give a very realistic effect, using Image-based lighting to light the scene. Alternatively, Exterior light studios may give you the effect you require. These do use physically accurate lights however, which generally take longer to render the scene.

Alternatively, you may prefer to use the Standard Light Studio as a starting point and build up your lighting from there, adding combinations of the basic recommended lights to create the desired effect..

The Standard archive contains a Default Eye Light studio (which is effectively rendering with a head light); a folder of Exterior light studios which predominantly consist of studios that use a number of lights to replicate the effect of a Sky light. Not using physically accurate lights means you don't have to turn on Auto Exposure (see ) which can negatively impact on the basic recommended light settings; a folder of Interior light studios for use in internal scenes; a folder of Object light studios which are best suited to lighting smaller models, such as a vehicle or piece of machinery, for example; and a folder of Projector light studios, which can be used to project an image onto an object in the scene.

The Templates archive contains all of the basic light shaders that are available. These can then be edited (as can all lights) to create the exact lighting you require (see for more information on editing lights).

Adding lights to the scene

From one of the archives in the left hand pane of the Lighting tab, choose the light you wish to add to the scene.
Drag the light and drop it into the palette (right hand pane of the Lighting tab). This will automatically be added to the scene. To reposition the light within the scene, see >Positioning lights in the scene

Note
If you drag a light studio into the palette, this will replace any existing lights with those that make up the light studio.

As a general guide, the more lights there are in a scene, the longer it will take to render it photorealistically. For external rendered scenes, you may consider using the Standard Light Studio , (from the Recommended archive) as a starting point, then strategically add a couple of Point and Spot lights around the scene, (Point lights are good to light up a dark area of the scene, whilst Spot lights can add an element of drama and enhance realism).

Positioning lights in the scene

Having added a light to the scene (see >Adding lights to the scene, double click on it, or right click and choose Edit... from the context menu, to open the Light Editor , (see
Point, distant, spot and projector lights have a Location parameter. Distant and spot lights additionally have a To parameter. You can type in x-, y-, and z- coordinates for these, or alternatively use the Pick button to interactively pick a point in the scene where the light and/or target is located. The light is represented by a 3D wireframe sun icon in the scene and the target by a wireframe sphere. The currently selected light is drawn in the selection color (see the section called "Selection Options" in chapter called "Selecting Items" in the Roamer book for more information on this).

Note
JetStream does not allow you to pick a point in empty space so you must pick a point on the model.
Lights can be positioned interactively. The 3D wireframe sun icon, representing the light, has six bars extending out along the x- axis, y- axis and z- axis. Hover the mouse cursor over one of the bars. The cursor will change to a hand and the bars will extend further along that axis. Hold the left mouse button down to hold on to the light and move it in either direction, along the extended bar. Release the left mouse button to release the light in its new position. This can be performed for all three axis.
Lights can also be positioned in the current location of the camera, which can be anywhere in the scene. Navigate to the location where you wish the light to be positioned. Right click on the light in the palette (right hand pane of the Lighting tab) and choose Position as Camera from the context menu.

Note
Not only will this position the light in the same location as the camera, if the light has a To parameter, this will also be set to the focal (or Look At ) point of the camera.

Managing Lights

The palette is where you edit and manage your lights for your scene. Lights are taken from the archives into the palette where they are edited.

Managing palette lights

Right click on a light in the right hand pane of the Lighting tab (the palette).
Click Delete to delete the light from the palette. This will also remove the light from the scene.
Click Copy to copy the light to the clipboard. Right click on an empty space in the palette and choose Paste to paste a copy of the light with the same name suffixed with the next number in the list.
Click Rename to rename the light. You can also select the light and press F2 to rename it.
Click Clear Palette to delete all the lights from the palette and hence from the scene.
Click Edit... or simply double click on a light to open the Light Editor dialog, allowing you to edit its parameters. See for more information on this.

Editing Lights

You can edit a light in the palette by double clicking on it, or right clicking and choosing Edit... from the context menu.

There are six types of light visible in both OpenGL interactive renders and photorealistic renders:

Ambient lights give a general background light to the scene and therefore only have intensity and color parameters.
Eye lights are located at the viewpoint and also only have intensity and color parameters.
Point lights have a location but shine in all directions. They also have an intensity and color and additionally can cast shadows (only available in a full photorealistic render).
Distant lights are directional and so have a location and target. However, the location and target merely set up an axis down which the light shines, as these light types are infinitely far away and their beams are parallel. As well as intensity and color parameters, they can also cast shadows in a photorealistic render.
Spot lights are also directional and therefore have a location and target, as well as intensity, color and shadow parameters. In addition, they also have parameters for affecting the light's fall off and cone angle, as these light types are not infinitely far away, so do spread their light over a cone and the intensity does diminish away from the light.
Sun simulates the sun's light. The orientation of your model is defined by north and up directions. The position of the sun is specified as azimuth and altitude. If the sun's mode includes "Position", you can input your location on earth, the time (using local time zone) and date and Presenter will calculate the sun's azimuth and altitude for you. If the sun's mode includes "Intensity", Presenter will also calculate an accurate intensity for the sun based on position, time of year and atmospheric conditions.

There are an additional three types of light visible only in photorealistic renders:

Projector lights are used to project an image onto surfaces. You can define the file of the image to be projected.
Sky simulates the illumination from the sky (but not the direct contribution due to the sun itself). The orientation of your model is defined by north and up directions. The position of the sun is specified as "sun altitude" and "sun azimuth". Whilst the direct contribution of the sun is not included, its location will determine the appearance of the sky hemisphere. If the intensity is left at 0, Presenter will calculate an accurate intensity for you based on the sun's position.
A Goniometric light is one which can emit widely varying amounts of light energy in different directions. One goniometric source could behave exactly like a point light, another could behave exactly like a spot light, and a third could look nothing like either of those. A goniometric light gets its intensity distribution function (how much light goes in any one direction) from an industry-standard file. Presenter supports CIE (*.cie), IESNA (*.ies), CIBSE (*.cib) and ILUMDAT (*.ldt) files.

Note

A complete reference manual for all light types is included with the JetStream API (see \'API\'COM\'documentation\'shaders.chm). The JetStream API is included with JetStream Roamer and can accessed via the JetStream installer menu.

Each light type has its own parameters, and the editor for a Point Light is shown here:

Point, distant, spot and projector lights have a Location parameter. Distant and spot lights additionally have a To parameter. See >Positioning lights in the scene for more information.

Note

When the user profile (see the section called "Profiles" in the chapter called "Interface" in the Roamer book for more information on this) is set to Developer , the dialog will include a full list of available parameters and allow you to change the type of a light.

Point, distant, spot, sky, sun, projector and goniometric lights have a Shadows parameter. See Shadow Casting for more information.

Editing parameters in the dialog will interactively alter the scene with those changes.

At any time, click on the Apply button to apply the parameter edits to the light in the scene.

You can save an edited light for use in other scenes by simply dragging it onto the My Lighting user archive.

Click OK to keep the changes made or Cancel to discard any changes made (since the last time you clicked Apply at least).

Shadow Casting

Checking the Shadows check box in the Light Editor of a light that supports shadows (Point, distant, spot, sky, sun, projector and goniometric) result in the selected light casting shadows in the scene. Shadows will only be visible in photorealistic renders; unless you are using a Hardware accelerated OpenGL 1.5 compliant graphics card, in which case you can preview Interactive Shadows . See the section called "Presenter Options" in the chapter called "Display Model" of the JetStream Roamer book for details on how to display interactive shadows and lighting.

Note

Enabling shadows on lights should be given due consideration. If you turn on shadows on all lights, then you may find the effect very confusing and somewhat un-natural, especially if there are many lights in a small scene. This will also have an affect on performance, during navigation and general refreshing of the navigation window. You may wish to consider only enabling shadows on a few strategically positioned lights, to create the effect you require.

In addition to choosing which lights in your scene will cast shadows, you may also select which items in the scene should cast a shadow. Each item in the scene has its own shadow casting option.

The available shadow casting options available for an item, are:

Off . Choose this to disable shadows. The selected item will not cast a shadow from any light source.
On . Choose this to enable shadows. The selected item will cast a shadow from any light source that has >shadows enabled.
Inherit . Choose this to inherit the shadow casting option from the parent item. i.e. the selected item will use the same option as the item directly above it in the Selection Tree path (see the section called "Selection Tree" in the chapter called "Selecting Items" in the JetStream Roamer book for more information on the selection tree and its structure). For example, if you turn shadow casting On for a Group and the Geometry contained within that Layer is set to Inherit , then the Geometry will cast shadows also, as it inherits the On option from its parent (the Group).

Note
If all items in the scene are set to Inherit then the default setting is On

To set an items shadow casting option:

Right click on an item in the scene, select Presenter from the context menu and then choose the >shadow casting option you require.

Note
The item selected will depend on your Selection Resolution setting. See the section called "Selection Resolution" in the chapter called "Selecting Items" in the JetStream Roamer book for more information.

Right click on an item in the Selection Tree (see the section called "Selection Tree" in the chapter called "Selecting Items" in the JetStream Roamer book for more information), select Presenter from the context menu and then choose the >shadow casting option you require.

Advanced Lighting

JetStream Presenter is capable of many advanced lighting effects, including soft shadows physically accurate lighting simulation, volumetric lighting effects and Image-based lighting

Soft Shadows

JetStream Presenter includes shadows generated from pre-calculated shadow-maps for each shadow casting light source. The use of shadow maps enables rapid rendering of shadows with soft or graduated edges. The shadow resolution can be controlled to balance performance and image quality.

Soft shadows are only suitable for use with small models and are disabled by default. For large models the generation of the shadow maps can use excessive amounts of time and memory. Soft shadows generated for large models are often too vague and dispersed without using an excessively high resolution, which uses even more memory and time.

Physically Accurate Lights

By default Presenter uses lights with unitless, or empirical intensities. These are physically meaningless and are just chosen to give a visually pleasing result. Presenter can also use physically accurate intensities. These are defined in real world units such as Candela, Lumen or Lux. However, once we start using lights with real world intensities, we start to produce images with a real world variation in luminance values.

By default Presenter uses lights whose intensity remains constant as you move further from the light. In the real world intensity is reduced proportional to the inverse square of the distance from the light. Changing a light's "Fall Off" parameter to "Inverse Square Law" will more accurately model a light's fall off in intensity. However, once we start using lights with real world fall off, we start to produce images with a real world variation in luminance values.

In the real world, the human eye is capable of resolving images in extremely varied lighting conditions, ranging from bright sunshine reflecting off snow to a room lit only by a single candle. In computer graphics on the other hand, we need to produce an image on a display device which has a very limited range of luminance values. Therefore it is necessary to compress the range of luminance values found in a real world scene into the displayable range in such a way as to produce a realistic looking image.

Photography, of course, has exactly the same problem. If a photographer (or camera) does not take into account the light levels in a scene before calculating the exposure of the shot, the likely result will be an image which is either over-exposed (everything is too bright) or under-exposed (everything is too dark). A professional photographer will also use different speeds of film for different lighting conditions. The aim is to produce an image on film that is representative of how that scene would have looked to a human observer.

Presenter includes an "Auto Exposure" option (see ). When enabled, Presenter will render the image twice. Once to sample the range of luminance values in the output image, then a second time to render the actual image with the luminance values adjusted to match the behavior of the human eye.

In general, when using physically accurate lights, "Auto Exposure" should be on.

Volumetric Lights

Volumetric lighting allows effects such as the scattering of light, by fog or smoke, in a scene. Enable the "Scattering" check box on each light. A "Scattering Medium" foreground effect must also be in use (see for more information on how to setup foreground effects).

You may need to adjust the "Medium Density" and "Medium Ambient" parameters of the "Scattering Medium" foreground effect to suit your model. If no volumetric effects are visible, the "Medium Density" is too low. If the rendered image is entirely white, the "Medium Density" is too high.

The default medium is plain white. Optionally, a "density shader" may be set to any solid (not wrapped) color shader, to create the effect of a non-uniform (inhomogeneous) medium. Examples of shaders that can be used are "Blue Marble" and "Solid Clouds". A shader that has been designed explicitly for this purpose is the "Turbulent" shader.

The key points when using volumetric lighting are:

Remember to turn the "Scattering" parameter of light sources on if you want to see their volumetric effects.
Use "Medium Density" and "Medium Colour" to define brightness and colour of the lit medium.
Use a solid color shader set as "Density Shader" for simulation of density variations in the medium.
Decrease "Error Bound" if image appears spotty outside shadow areas.
Increase "Min LOD" parameter if areas with volumetric shadows appear spotty.
Set high "Error Bound" and small "Min LOD" for fast previews.
Use "Inverse Square Law" for your light's "Fall Off", together with auto exposure, for best results.

Image-based Lighting

Image-based lighting, simply put, is where an image is used to light a scene. In the real world, every object is lit not only by light sources like the sun, lamps etc, but also by everything around. Standing in the middle of a street, a person will be lit by the sun, the blue sky, the brown buildings and the grey floor. Emulating this form of lighting clearly has the potential to create incredibly realistic images.

Images used in this lighting method are a special kind of image called a High Dynamic Range Image or HDRI. This type of image has the capability of lighting a scene with incredible accuracy. In Presenter an HDRI is wrapped around the scene as a sphere, and colour and brightness from the HDRI are cast onto the 3D model to light it.

To give an example of the difference this can make, this is a before shot using normal lights

and this is the same model lit with Image-based Lighting

It is clear the difference this form of lighting can make to rendered images. And the enormous advantage here is that it is much easier to set up than traditional lighting.

Image-based Lighting Setup

On the Lighting Tab, click on the Recommended folder in the left hand side of the palette.
Drag the Environment Light Studio into the palette on the right. This replaces all lights that were in the palette with an Ambient and an Environment light containing our High Dynamic Range Image.
Click on Render to render the scene using the default image contained in this Environment light. This type of render can take slightly longer than traditional lighting methods, but the results are worth the extra time invested.
To use an alternative sample image, click on the Environment folder on the left to show another two example environment lights; a Sky (used in the example above) and a City. Drag the City light over to the right to replace the Environment light in the palette (which should be deleted before rendering).
To manually insert a new HDRI, double click on the Environment icon in the palette, select the Edit... button next to Environment, click on the button next to Filename, and browse to the .hdr file required. For this to work correctly, this HDRI must be a Light Probe HDRI. (Additional Light Probe HDRIs are available from a variety of places on the internet, including Dosch Design.) Click on OK in both dialogs to set the new image to be the light source, and click Render to produce a newly lit rendered scene.