CATIA Photo Studio - cadcamlab.org Studio.pdf · CATIA Photo Studio CATIA® V5R19 Lighting As you’ve noticed so far, your scene displays adequately with default lighting. However
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Photo Studio is used to produce professional, print-quality images of your product. It letsyou create a range of styles from photo realistic to illustrative images. You can also createsimple animations of models and products.
As you’ve noticed so far, your scene displays adequately with default lighting. Howeveryou can use Photo Studio’s many lighting tools to create a truly compelling shot. Lights letyou focus attention on different objects in the scene. They also let you create a certain look,or ‘mood’ to the scene. This section shows you how to create different light sources andhow to use them in order to enhance the look of your scene.
The first three icons create Standard lights, also called Punctual lights. These optionsconsist of spot lights, point lights and directional lights. The last four icons create differentArea lights, also called Surfacic lights. The options for Area lights are rectangle, disk,sphere, and cylinder.
Standard lights create only sharp-edged shadows, while Area lights create shadows withsoft-edges. Standard lights generally require less processing and render faster than Arealights. The following shots show the effect of Standard and Area lights. Notice thedifferences in shadow quality. Both shots are rendered with the Anti-aliasing set to Highand a resolution of 1200 x 900 pixels.
Standard Spot Area Disk Light
Note: It is possible to use both light types in one shot.
Select the Create Spot Light icon. The spot light appears as a cone with greenmanipulator handles at its top and base. The manipulator handles will only appear if thelight is selected. The top handle is the source point for the light, representing the location ofthe light. The source point rotates the spot light around the bottom handle, the target point.
The handles are similar to those you saw when you worked with cameras. The sphererotates the light; the line translates it; and the square does both.
Spot lights are the most frequently used lights. They’re used to light individual objects in ascene. They are not used to light the entire scene uniformly.
Select anywhere in the work area to deselect the spot light. Notice that the deselectedspot light is represented with a star at the apex of the cone. An arrow points from the startoward the base of the cone. The star is called the anchoring point, it shows the location ofthe light source. The arrow is called the direction vector, it shows the direction that the lightis shining.
Delete the spot light from the specification tree.
Select the Create Point Light icon. A point light is created. Point lights emit lightin all directions, like a light bulb.
Deselect the light. Notice how point lights are represented when they’re unselected. Theyhave a central anchoring point, but no direction vector.
Select the Create Multi-View icon and select the point light. This gives you abetter view to see the effect of manipulating the light’s handles.
Drag the handle by the sphere. The handle rotates in any direction. It’s important torealize that the light itself doesn’t rotate, only the handle. Since point lights emit light in alldirections, rotating a point light would have no effect. After rotating the handle, the newdirection the handle is pointing is the new direction that you’re able to translate the light.
Drag the handle by the line. The light translates along the axis that the handle is pointing.To translate in a different direction, rotate the handle again, then drag by the line.
Drag the handle by the square. Notice that you can translate the light freely.
Select the Create Directional Light icon. A directional light is created.
Deselect the Directional Light. You are now able to tell which way the light is pointing bythe vector direction.
You can clearly see the anchoring point and the direction vector. Directional lights emitlight at a constant intensity in one direction. Since the light intensity doesn’t diminish withdistance from the light source, directional lighting can light an entire scene, similar tosunlight. They are not used to light individual objects in the scene.
The other type of light is Area lights which consist of four shapes: rectangle, disk, sphereand cylinder. It’s also possible to change an existing Standard light into an Area light. Theproperties of a light allows you to be able to customize the light to your needs.
Right select on the directional light in the specification tree and select Properties. TheProperties window appears.
Lighting Tab
Notice the Lighting tab is divided into two areas, Source and Attenuation. The Source arealets you change the light’s Type and parameters for that Type. The Attenuation area lets youcontrol how the light attenuates or fades over distance.
Source
Type Allows you to switch the type of light
Angle Adjusts the angle of the light
Color Changes the color of the light. Every light Type has a Colorparameter. Refer to the Stickers section for a discussion of theLighting tab’s Color parameters.
Intensity Modifies the intensity of the light. Every light Type has an Intensityparameter. Intensity refers to the brightness/dimness of that light.
The Intensity icon opens the Intensity window. It is only active
in real time rendering.
Attenuation
Falloff Adjusts the diminishing of light between the source and target
In the Source area, select each of the three different Type options and notice whatparameters are available for each.
Notice that the Angle parameter only applies to Spot lights. Also notice that selecting adifferent light Type changes the light’s icon in the specification tree.
Change the Type to Spot and adjust the Angle value to its maximum and minimumvalues. Notice how the cone of the light changes. The cone shows you the region the lightilluminates. The Angle parameter, therefore, controls the area of illumination.
90deg for widest area of illumination
0.057deg for narrowest area of illumination
Select OK to the Properties window. Since you initially opened the properties for adirectional light, the options you’ve been looking at only apply to the Standard lights; Spot,Point, and Directional lights.
Turn on the Create Multi-View icon. Make sure you have good views of the sideand front of the light.
Re-open the Properties window for the light and select the Area tab.
Select each of the Type options available and experiment with changing the values forthe parameters that are available for each Type. Notice how the light changes in thework area.
Angle
Even though it’s not available on the Area tab, the Disk and Rectangle lights have an Angleparameter as well. To change the Angle value through the Properties window you mustswitch back to the Lighting tab.
With the Type set to Rectangle, select the Lighting tab and change the Angle parametervalues. Notice how the light changes in the work area.
Select OK to close the Properties window. You can also change the Angle in the display.
Select the light in the work area and move the cursor over the side of the cone. Acurved arrow, the angle manipulator, appears when you have successfully selected the side.
Attenuation is the diminishing of light from full strength (at the light source) to zero (at thelight target) within the perimeters of the light. Think of the perimeter as the boundary of thelight, i.e., the cone that encloses the light. The perimeter is what you see when you selectthe light.
Another name for attenuation is falloff. All lights, except directional lights, have falloff.Directional lights shine at a constant intensity over an infinite distance so there is nodiminishing of light.
Under the Attenuation section of the Lighting tab, select the drop down menu forFalloff. You can choose from three types.
The End parameter sets the point where attenuation ends or the point where the light falls todarkness. Objects outside the End parameter are not lit by the light. You can set the Endvalue from the Properties window or you can set it from the work area by dragging thelight’s end modifying handle.
Select OK in the Properties window.
With the light selected, move the cursor over one of the end lines at the target end ofthe light. A green, double-headed arrow appears.
Drag this manipulator to shorten or lengthen the attenuation range.
The Start Ratio adjusts the fall off range, letting you determine where full illumination willbegin. A Start Ratio of 0.0 means that full illumination starts at the light source; a value of0.5 means that it begins half way between the light source and target point; and a Start Ratioof 1.0 means that full illumination starts at the target point, so that there is no falloff.
Open the Start Ratio document from the Start Ratio directory.
Access the light’s Properties window. Notice that the Start Ratio in the Lighting tab is setto 0.1. The light should appear as shown below.
Perform a quick render. The house is barely illuminated.
Now set the Start Ratio to 0.9 and perform another quick render. The light intensity onthe house has increased because the Start Ratio is closer to the house.
The Angle Ratio determines how hard or soft the edge of the light is. Only spot, rectangle,and disk lights have this parameter.
Open the Angle Ratio document from the Angle Ratio directory and look at the lightsetup. The light is focused on the front of the birdhouse, and the target point is locatedabout halfway to the back of the birdhouse.
Double-click on Camera 1 from the specification tree.
From the viewpoint of Camera 1, perform three renders, with the Angle Ratios of 1.0,0.5, and 0.25. Renders with Angle Ratios of 1.0, 0.5 and 0.25 are shown below.