COMPUTER
AIDED
ARCHITECTURAL DESIGN
Workshop 6
Notes,
Week of October 1, 2018
INTRODUCTION TO LIGHTING AND RENDERING
These notes will introduce basic lighting and rendering through Rhino Render and continue on to more advanced options using the Rhino plugin for V-Ray. Additional notes are provided on the plug-in for Maxwell for comparative purposes only. They are for optional reading only and the techniques are not required for the class.
PART 1. LIGHTING
1. Create a Rhino Model with a ground plane surface and three solids as follows:
2. Open the lighting icon from upper right-hand side of screen.
3. Place a spot light in the model from the front view, entering the target and radius first, and then the light location second.
4. Select the light and turn the control points to on.
5. From the top view, move the lighting source position to the +x, -y position relative to the ground plane.
5. Activate the perspective window, select the rendering icon, and render the view. Note that the background color in these renderings is black rather than defaulting to white. See the technique discussed later in these notes as to how to change the background color.
6. Following a similar procedure, create a back spot light pointing towards the center of the model and create a rendering.
7. Select the properties icon for the back light and reduce the shadow intensity to 0 and light intensity to 50.
8. Change the resolution to a mid-level size at 1280 x 720 (16:9) rather than default to the view window size. Note in the last rendering that there are stair step like lines on geometry running diagonally across screen (they are jagged), such as on the cone and the box. To compensate for this problem, which is called "aliasing", change "Quality" to "Good Quality " to set up for a higher quality "anitialiasing" in the dialog window below.
Also, in the same dialog box, to change the background of the rendering, select Background "Solid Color" and select the color swatch (which is white by default in the screen capture below) and change it to black. Select the "OK" button at the bottom of the dialog box to exit back into main modeling mode of Rhino.
Render the perspective window again and note that the second light is no longer casting a shadow and also that now that there is a black background.
9. Add a point light to the upper left hand corner of the model. Here it is only necessary to position the light source. That is, the point light is an omnidirectional light and doesn't have a target or cone profile. Begin in the front view and continue to place the light in the top view similar to setting the light source locaation for the spot lights.
10. Using the properties icon, adjust the shadow intensity of the point light to 0 and change the light intensity to 50 (i.e., 50%).
11. Render the perspective again for a rough simulation of three point lighting.
PART 2. RENDERING
1. You can continue to adjust the antialiasing level by rendering the same model within a more advanced rendeing tool as we will see in a later workshop tutorial.
2. Using the same properties icon as before, set the material colors of the box, cylinder and cone to red, blue and green, and also make the cone transparent. Note that the "Material" pull-down tab is active, that the "basic" assign by method is selected, and that for the cone, the transparency value is set to 0.75. Do not select the "Transparency Check Box" which refers to a separate material property.
5. Rendering the view to 640 by 480 pixel resolution results in the following jpg file.
6. Download the image of penguins below by right clicking on it and saving it to your local working folder.
7. Now select the ground rectangle, open up the properties dialog, select the "material" (tube) icon, select the check-box for "Bump" and also "empty - click to assin" link highlighted in blue in the image below. Load the file above through the map file interface.
Render the result.
8. Within the same dialog box, go to the texture mapping, which looks like a half roled sheet of paper, and select the planar texture mapping icon.
Trace the surface in the ground by a rectangle from the lower-left-hand corner to the upper-right-hand corner.
Now, continuing in the texture mapping dialog box, adust the "UVW repeat" parameters to 2.0, 2.0, and 1.0.
Re-render the image and note that the bump map is repeated twice along each axis.
PART 3: LIGHTING AND RENDERING WITH V-Ray
Part 3 is an introduction to rendering techniques with V Ray. We will introduce basic rendering methods through V-Ray for this first tutorial and then return with more advanced treatments of materials and lighting in the workshops to follow. For a more general guide and tutorial material on V-Ray see https://docs.chaosgroup.com/display/VRAYRHINO
More tutorials and reference materials can be accessed from within Rhino from the menu item V-Ray/Help/Online Help. This menu item links to an online Rhino Help site at Chaosgroup.
For a slightly older PDF documentation of the V-Ray plugin to Rhino see the V-Ray For Rhino Plugin Manual. However, the user interface has changed and new functionality has been added.
In the later part of this part 3, we will switch to a V-Ray Sun. First, select the sun icon in the Rhino "Render Tools'' and using the pop-up dialog box change the check-box to turn it off.
1. To change rendering engines from Rhino Render, go to Menu
item Render> Current Render>V-Ray For
Rhino
2. Using the same techniques as described above, create a file with a ground plane with three objects, a box, a sphere, and a cone.
3. Using the VRay lighting tab, create a key light, back light and fill light without determining intensities and other properties.
4. Select the spot light in the front right-hand area of the 3D model, and in the properties dialog box, select the "spotlight" icon, and note specifically that the color is white, intensity is set to 30.0 scalar units (a relative measurement of intensity rather than specific energy units), and that the shadows check-box is on. . Select the "Edit in V-Ray Asset Editor and note the appearance of the dialog box named "V-Ray Asset Editor.
5. Within the "V-Ray Asset Editor, select the arrow pointing to the right on the midde of the right hand side, and the asset editor expands as shown below. Note again that the color is white, intensity is set to 30.0 scalar units. Note allso that the cone angle and the penumbra angle are indicated in this expanded view of the asset editor.
6. Select the spot light in the rear back right-hand side (i.e., the back light). Set the intensity to "15" and uncheck the shadows checkbox.
7. Now select the point light, and also set the intensity to "15" and the shadows to off.
8.Select the rotary symbol, 4th from the left, open the "Camera" tab, and select the arrow to the right of the words "Standard Camera" to expand the camara options.
9. Set the F-number (F-stop number) to 3. The F-number is a number determined by the aperature opening of the simulated camera. A lower number corresponds to a wider aperature opening that increases the exposure to light. A high F-number corresponds to a smaller aperature opening and the lowers the exposure to light. (Note that the actual calculation of the F-number is based upon a the ratio of the focal length to the diameter. That is, F-number = focal_length/diameter. Thus, the greater the diameter of the opening the lower the F- number. ) Set the Film Sensitivity (ISO)" to 100 and the and the Shutter Speed to 200.
7. Select the "Perspective" window, choose a desirable view orientation, and then select the Render Icon (the blue sphere) and render the perspective view.
If the rendering is too
dark, return to the camera editor, and try lowering the shutter speed
or f-stop number.
Note that a slower shutter speed means that the shutter remains open
and thus
admits more light. Conversely, increasing the shutter speed will
decrease the amount of light entering the camera.
Alternatively, as described previously, lowering the F-number value of
the camera means that the
camera aperature is larger and that the camera will admit
more light. Conversely, a higher F-number correspondends with a smaller
aperature and will decrease the amount of light entering the camera.
However, lowering the F-number may be used to increase the depth of
field, a measure of how much within the view lies in focus. This is
a technique that will be discussed in a later workshop.
7. For another approach, within the V-Ray Buffer Window, turn on the icons in the lower left-hand corner for "show color corrections control", "color corrections level", and "use exposure correction" (see icons highlighted by arrows in lower left hand corner of image below).
8. The "show color corrections" icon will open the "Color corrections" window. Within the window adjust the left and right "gradiant" slider (the values at the ends of the range are 0.76 and 9.63 in the image below) to produce a desired contrast and brightness level.
9. Within Rhino, select in turn each of the lights in the 3D model, and turn off the "enabled" check-box in order to turn off the light.
10. Go to Render Tab, and toggle off the standard Rhino "sun" symbol. Next, go to the V-Ray Lights panel and select the sunlight to turn on the Sun control panel.
Within the Sun control panel, set the Sun to "On", and determine the time and day of the year, as well as set the location either by picking a city (e.g., Richmond, VA) or entering the exact latitude and longitude.
Hit OK in the dialog box above. Also, at the Rhino command prompt, hit the return key or right mouse button to place the sun light symbol at the origin of the x-y plane.
Render to see the impact of the direct sunlight. If necessary, adjust either camera settings and/or the exposure to arrive at a good light level and contrast and turn on "White Balance" so that the color is appropriate to the time of day. That is, note that the Sun impact on the objects in the Rhino model is tinted to reflect the color temperature of natural daylight.
6. To control image resolution, go back to the V-Ray Asset Editor and open the "Rnder Output" tab.
Change the Aspect Ratio resolution to 16:9 widescreen and Image Width/Height to 960 x 540 and test render.
Render again, and within the V-Ray frame buffer, select the floppy-disk "Save image" icon highlighted below, and save the image to the jpg format.
7. To create materials, return to the V-Ray Asset Editor and select the first icon in the upper left corner.
Within the Material Editor Dialog Box, select the "Add Material" Icon in the lower left-hand corner and choose "Generic Material":
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Next, right mouse-button on the word "Generic" and rename the materials glass1.
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Select the "Quick Settings" tab and note the default settings for Diffuse, Reflection,Refraction, Glossiness, IOR (Index of Refraction) and Opacity as follows.
Select the "Quick Settings" tab and adjust the default settings for Diffuse, Reflection,Refraction, Glossiness, IOR (Index of Refraction) and Opacity as follows.
Select the sphere, right mouse-button click on the "glass1" material in the "Material List" tab of the asset editor, and choose the option to "Apply Material to Selection".
Return to the "Output" tab of the V-Ray option editor, and with an aspect ratio of 4:3 lower the resolution to 640 x 480, and do a test rendering:
Return to the V-Ray material editor, adjust the opacity of the glass1 material to 1 and render again.
Return to the V-Ray material editor,
create a generic material "myCone", select the Diffuse layer tab, and
change the "Color" to cyan, and assign the color to the cone.
Similarly, create a material "myBox", select the Diffuse layer tab, change the "Diffuse Color" to a light brown, assign the color to the box and render the result.
8. Using a background Sky with the V Ray Sun
In this step, we switch from the Rhino Sun to a V Ray Sun. First,
select the sun icon in the Rhino "Render Tools'' and using the pop-up
dialog box change the check-box to turn it off. If not already active,
ensure that the V Ray Sun is turned on and appropriately placed in the
Rhino model file.
9. Controlling the Sky Color
Return to the V Ray Asset Editor and Settings icon at the top of the dialog box, and open the "Environment" tab.
Select the checkerbox icon adjacent GI skylight, and within the V-Ray
texture editor, change the "Sun" to "/Sun Light" (the V-Ray sun) and
change the "Sky Model" to "Preetham et al', and select the "Back"
botton at the bottom of the editor.
Similarly, select the Select the checkerbox icon adjacent to background and also pick the V-Ray sun with Preetham et. al.
m
Adjust the perspective view to look at the horizon and render with the the sky background.
Note, however, that the ground appears to be a field of brown. This is an effect of the sky simulation program.
A simple workaround to this effect is to extend the groundplane so that is occludes the lower part of the background.
Another technique is to select a color for the background and intensify its value, such as to the number 7 in the setting below, and combine it with the simulated Sky background. However, this begins to step away from a more purely simulated result.
Return to the V-Ray asset editor, set the background back to
black and intensity one, and under the linked menu for the sky, lower
the" turbidity" to value to 2.0 in order to make the sky less hazy, set
the ozone to 1, and set intensity to 2, and select the "Back" button..
Re-render the perspective view and note the moderately deeper blue color of the sky as compared with the earlier rendering.
9. Working with a predefined materials library.
With the V-Ray asset editor, right mouse-button click on "Materials" icon (shown below) and select the left arrow to select predefined materails and drag them into the materials list for the Rhino file . For example, here a type liquid/ocean procedure map is loaded.
