ALAR 6712  Studio Workshop Spring 2010

Workshop 11 Notes, March 16, 2010

Basic Lighting and Materials, Introduction to Particle Tracing

Note that the new version of Microstation uses Luxology as a rendering platform. The older version of Microstation uses both Luxology and a more direct rendering Engine. Since Luxology is in its initial rollout stage, there are some areas where it isn't as complete as the more established rendering engine. Therefore, for this set of workshop notes and the next set, workshop 12 notes, primarily for pedagogical reasons, we will use the older version Microstation V8i, and not the MicroStation CAD v8i Select Series 1. Note, for your personal copy of Microstation, please download and run the file "Luxology-18a.exe" from the classes folder "luxologyupgrade".

1. THREE POINT LIGHTING

Three point lighiting is a technique developed in film-making and still photography. It typically consists of a "key" light pointing into the model at higher instensity such as can be achieved with a directed "spot light" from the forward upper right hand side. This establishes the key shadows and lighitng contrast. Second, a back-light points into the model to establish a greater effect of three-dimensional depth, such as a "spot light" pointing into the model from the rear upper right-hand side of the model. This second light is generally at 1/2 to 3/4 intensity of the key light. Third, a "fill" light that is a middle intensity omni-directional light is placed in the upper forground of the model to establish middle grey tones and offset the high contrast establised by the key light. This is can be done with an omni-directional or "point" source light placed in the upper left hand foreground of the model and set to roughly 1/2 to 3/4 intensity of the key light. In the Microstation drawing, the lights are represented by symbols. The symbolic geometry for these lighting fixtures includes a lamp like symbol for the directed or spot light, and an asterik shaped symbol for the point source light. This setup has been already established in the file stillLife.dgn which is located in the classes/examples/lightingexample folder.

Three point lighting symbols on "construction" level	ray trace of three point lighting

Note that the light symbols reside on the "construction" view window attribute. You can turn on or off this attribute by going to the view attributes dialog box in the upper left-hand corner of the view window. In the dialog box that follows, you select to on or to off the "constructions" attribute (image below at right). If this attribute is on, then the light symbols are visible. The "constructions" attribute should be turned off for rendering the model.

open view attributes dialog box	toggle on or off the view attributes to see light symbols

Using the rendering icon Q1 or choosing the render view tool from the view window icon, select Render Mode as "Ray Trace" and set Antialias to Medium to determine the rendering type and quality.

Click inside the view 2 window to ray trace the view, and the resulting rendering will appear as depicted in the image below:

2. LIGHT MANAGER

Load the file stillLife.dgn from classes into Microstation. We begin by creaing three vertical lines that will provide a kind of geometrical scaffolding to help place the lights. Do this with the "Place SmartLine" tool from the "Drawing" task menu, and locate the lines at the corners of rectangle. Also, use a the "F" key to ensure that Accudraw rotates into the front construction plane.

Three vertical lines placed in the model are situated to locate three lights above the ground.

From the visualization task menu, select the Place Light tool w2.

In the dialog menu for the Place Light too, choose the spot light lighting type. Use this spot light to create a so-called   "key light", set the lumens  to "1500", color to  "white:, intensity is "100", and the shadow casting to "sharp" (these are typically the default settings),

Enter two data points in the view window, one on top of the front-right vertical line to set the light source position, and second on the bottom right-hand corner of the cube to target the light.

Now place a second spot light or the so-called "back light", first reducing the lumens to 750.

Similar to the key light, use two data points to place the light on the upper point of the back-rear vertical line and target it to the corner of the cube.

Finally, change the light type to point source light at 750 lumens, and locate it with one data point only on the upper point of the front-left vertical line.

Point LIght Selected	light is placed in upper-left of model.

Remove the vertical lines as they are no longer needed and ensure that the "constructions" view attribute is also turned off. Turn off the constructions level through the view attributes dialog box and render.

open view attributes dialog box	toggle on or off the view attributes to see light symbols

Rendering the model will then result in the following image:

3. THREE TIERS OF INFORMATION  ARE TYPICALLY  USED TO DETERMINE THE ASSIGNMENT OF MATERIALS TO OBECTS IN A MICROSTATION DRAWING.

These tiers, identified below, can be treated either internally to the Microstation dgn file or as separate and external files to the main Microstation DGN file. The advantage of handling them separately is that they are  portable for re-use with other Microstation files. If created as external files, then these files need to be included separately in any folder where the Microstration drawing files exists in order to support the rendering of materials.

3.1 Material Table (file extension ".mat" such as "myproject.mat") - Determimes the assignment of materials to objects in a cad model by one of two methods: 1) according to layer and color or 2) by direct assignment to individual objects. The Material Table file references Palettes (or external Palette  files) for the description of individual materials.

3.2 Palette (file extension ".pal") - Describes the definition of materials according to their property values (e.g., transparency). Typically a an external palette file is created for a group of materials that have similar qualties, such as palette for marble (e.g., "marble.pal") or a palette for wood (e.g., "wood.pal").

Materials within a palette can be defined according to several methods, sometimes in themselves referring to additional image files.

• Definition by properties (e.g. color)
• By procedure (e.g., a specific algorithm for brick or wood)
• By texture mapping (iterally draping an external image file onto a surface)
• By bump mapping (using the greyscale value of an image file to simulate the relief of a material).
• By transparency mapping (iterally draping an external image file onto a surface, with one color selected as transparent)

3.3 Image files, typically jpeg (pseudo 24 bit) or tiff (true 24 bit) are referenced in the definition of individual materials through texture mapping and bump mapping. Occasional such files may also be used in other rendering techniques such as background mapping (an image background to scene, environmental mapping (a six sided box that encloses a model and may be reflected by materials in it), and transparency mapping (an image with a designated transparent color, such as may be used to map figures, such as people or trees, onto a computer model).

4. STANDARD RENDERING

Rendering usually is established with creating one or more light sources. Here, we will setup a rendering with a sunlight set to 10 a.m. by using the Light Manager Dialog Box (tool W1 in the Visualization Task).

• Set Solar intensity to 100
• Use the default time (10 a.m., July 1, 2001)
• Set Ambient intensity to 30
• Set "Flashbulb intensity to 30

Note that if working on the above file from part 2, the point light and two spot lights are also listed in the light manger dialog box below. Double-clicking on the icons for these lights will toggle them on and off. Here, they have been turned off.

It is possible to render through selecting one of any number of standard algorithms as described in the lecture preceding the workshop. Select the render tool Q1 from the "Task List - Visualization" on the left-hand side of Microstation's Application Window:

If you toggle off the point and spot lights, and rely only on the ambient, flashbulb and solar lights, then you will get the rendering depicted in the figure that follows. Note that the brightness slighter at the bottom of the "render" dialog box will help to adjust the lighting level.

Go through the "Render Mode" portion of the render tool to invoke varied rendering algorithms from "Hidden Line" through "Ray Trace".

Six different rendering mode and antialiasing settings are tested to create the images captured in the table below.

• Hidden Line – Antialias: Medium
• Filled Hidden Line –Antialias: None
• Smooth –Antialias: Medium
• Phong – Antialias: Medium (you may also want to turn off or save shadow maps under Settings>Rendering>General lighting)
• Ray Trace –Antialias: None
• Ray Trace –Antialias: None
  
  
  

  Hidden Line	Filled Hidden Line	Smooth	Phong	Raytrace no antialiasing	Raytrace  antialiasing

  
  

5. MATERIAL DEFINITION BY PROPERTIES

For these examples, copy the classes folders examples/ptrace/ptrace & ptrace2 (ies example) to the local hard drive, and, within the folder ptrace, open the Microstation file ptrace.dgn.

To initiate material definitions, you need to follow three steps as illustrated below:

1. begin by creating a material table file
2. initiate or load a material palette file for the definition of individual materials
3. define individual materials

STEP 1: using the visualization manager on the left= hand side of Microstation's application window, select the "Visualization" task and then select the icon labelled "A1" (see image below) to open the "Material Editor" dialog box.

By default, the prefix name of the material table "PTRACE" (or if using an external file "PTRACE.mat") is the same as the prefix name of the dgn file ("PTRACE.dgn"). If using an external file, it should be periodically be  saved by selecting the menu item "Table" from within the "Material Editor" dialog box and using the "save as" option.

STEP 2: under the menu item "palette", select the word "new" to create a new palette file, such as the file "mypalette". If using an external file as well, then the file must also be saved by going to the menu item "Palette" and using the "save as" dialog box to save the file as "mypallete.pal" when materials are added to it.

STEP 3: Within the Material Editor dialog box, select the settings menu item, and turn on the advanced settings.

STEP 4: Begin to develop the definition of individual materials. Right click on the word palette, and select the option to create a "new material".

STEP 5: Name the material "mattbrown". Begin to set into place the attributes for the new material.

The above material "mattbrown" has some of the following properties set

1. color -base color visible by ambient light (brown color as shown)
2. dark/bright - brightness of material under direct illumination
3. dull/shiny -shininess or dullness of specular highlight
4. opaque/clear - transmissivity of material to light (level of transparency)

Once created, right-clicking on the name of the material and selecting the word "assign" opens yet another dialog box by which it may be assigned to an object in the dgn file. That is, assigning the material by level and color is achieved by selecting the object (e.g., the cube). This assigns the material to the layer and color atttribute of the cube object, not actually the object itself. Thus, all objects which have the same layer and color attribute are also assigned this material. (Alternatively, to assign a meterial to a single object, you would use the "attach" option in the same dialog sequence. However, this alternative approach is not recommended.

As illustrated in the "Material Editor" dialog box below, note that any dgn file, such as the file named "test.dgn", may load any number of palettes , such as the palette "mypalette" and the also the external palette file "metals.pal".

The above material "mycopper" has the following attributes:

1. color -base -color visible by ambient light
2. dark/bright - brightness of material under direct illumination
3. dull/shiny -shininess or dullness of specular highlight
4. opaque/clear - transmissivity of matarial to light (level of transparency)
5. Reflect - reflection of light

A highlighted check-box or a "+" symbol  appearing next to the name of the material indicates that it has been assigned to objects in the dgn file by either the "Level/Color" method or another method. The material "mycopper" is so highlighted below..

6. BUMP MAPPING

A bump map assigns a superficial relief map to a surface based upon an image file. The greyscale value of the image is used to simulate the appearance of a surface relief pattern on the object to which it is assigned. The bump map attribute must be turned on via the down arrow to the right of the word "bump" in the "Material Editor" (see image at right below). Next, the 3D checkbox next to the word "bumpy" is selected (see again  image at right below). The specific image is selected from a dialog box such as depicted in the left image below where the bump map "STUCCO2.JPG" has been selected. This is a simple jpg file loaded onto the local computer's hard drive. Alternatively,  a common location for  bump map images is provided with the software and is located in the directory :C:\Documents and Settings\All Users\Application Data\BentleyWorkspace\System\materials\bump". In the middle image of  the dialog below figure below, the file "STUCCO2.JPG" is selected for the bump map.

Note too in the middle image of the figure above that the size of the bump map has been set to "Master" units, typically 1 foot in area. This means that that bump map will scale to 1 ft by 1 ft on any surface to which it is applied. Also, note that the "repeat" option is selected for "X" and "Y". This means that the bump map will tile accross any surface that it is applied to. A bump map set to Size X of 0.5 and Size Y 0.5  in Master Units will tile at the scale of 1/2 foot by 1/2 foot. This can also be specified as 0:6 for 0 master units (feet) and 6 sub units (inches). 

Once the bump map parameters have been established, the material which references it is modified to have a surface relief pattern. The appearance of "mycopper" is changed accordingnly in the "Material Editor Dialog" box. This material can be assigned to the truncated cone in the dgn file.

7. PRE-DEFINED PALETTE FILES

In the Material Editor dialog box, and under the menu option "Palette/Load", you can also load a number of predefined material palettes. They  are locted on the hard drive of your computer as a part of the typical software installation. For a drawing file with a simple ground rectangle with three objects sitting on top of it (e.g., slab, sphere and cone), you can explore some of the pre-defined palettes as follows.

• Go to Palette>Open and choose C:\Documents and Settings\All Users\Application Data\BentleyWorkspace\System\Materials\pattern
• Open “finishes.pal” and assign “flat warm grey” to the cube. (go to “Assign,” then choose the object)
• .The material should then have a “+” next to it and contain the layer and color of the object selected.
• Open palette “glazing.pal” and assign glass to sphere.
• Open palette “metals.pal” and assign brass to cone.
• Open palette “floors.pal” and assign tile semi gloss to rectangle.
• To preserve the new settings, right-click on the table name and save and then on the palettes to save it to an external file. NOTE: BE CAREFUL. Rather than overwriting pre-defined system palettes, is probably better to save palettes under your own distinct names (e.g., "myglass.pal") and to rename materials within any given palette under distinct names (e.g., myflatwarmgrey) so as to avoid any confusion with system defined materials.

8. SAVING RENDERINGS (will cover next time)

• Change the window view size in Settings>Rendering>View size.
• Set to 640x480 (make sure “proportional resize” is off).
• Save image file by going to Utilities>Image>Save (check options and save by browsing to folder).
• To see image in microstation, go to Utilities>Image>Display .

9. PARTICLE TRACING / RENDERING

• Open ptrace2/ptrace-still.dgn
• Open the tool to change view size (settings/render/viewsize)
• Set the view size to 640 x 480
• Select “view attributes” and turn on "constructions" . . . see lights in the file
  
  
• Turn off constructions (view attributes/constructions off)
• Change render mode to particle trace
  
  
  
• Select magnifying glass adjacent line above "particle trace" adn to the right of the word "untitled" in the  particle trace dialog box .
  
  
• In the "Render Settings" dialog box, switch settings to  “Advanced Mode”. Note that the file had been setup to Use 50 million particles which is very high.
  
  
• Change the number of particles from 50 million particles  to 1 million particles for a quick test.
• Note also that the display type is "visual" which will produce a photorealistic result.
  

• Use visualization tools/light manager (W1 tool) to see lights listed and values
  
  
• Within the light manager dialog box, note that the point light sources have ies (Illuminating Engineering Society) data files attached. These files are supplied by lighting equipment manufacturers for their inventory of lighting fixtures.
• Illuminating Engineering Society (formed in 1906) (IESNA/IES) –Included honorary member Thomas Edison.
  
  
  
• Use the render tool to do a particle trace rendering for 1 million particles as specified in the Render Settings dialog box above.

• Change the render type to illuminance (light energy reaching the surface) in the Render Settings dialog box .
  
  
• Select the Display Current Solution mode  (shown in Render dialog box below) mode and re-render for illuminance.
  
  
• Note that the brightness control slider in the Render dialog box can be used to lighten or darken the image. This is like controlling the aperature on a camera to allow for a greater or lesser film exposure.  The level of light energy isn't changed. Only the recording of the light energy is modified by adjusting this setting, similar to changing the fstop control on a camera.
  
  
  
• Use the render tool to do a particle trace rendering for 1 million particles as specified in the Render Settings dialog box above.
• Change the render type to luminance (light energy reflected  by  the surface)in the Render Settings dialog box , and re-render for the current solution.
  
      
• The second icon at the bottom of the Render dialog box can be used to increase the number of particles by whatever amount was specified in the Render Settings dialog box above. In this case, since 1 million particles had been specified, the rendering would be completed with an additional 1 million particles. That is,  existing energy solution is added on to with 1 million particles.
  
  
• Returning to the Light Manager dialog box, it is possible to change the lighting fixture.
  
  
  
• Within the Light Manager dialog box, select a new lighting fixture's IES data file.
  
  
  
• The data file 1104FR.IES is for a lightolier fixture: Spill Ring 12" Aluminum Reflector (1-lamp)
  
  
  
• Re-render for Iuminance with the new lighting fixture and note the more diffuse light as depicted on the left-hand side in the image below.. 
  
  
  
  
• A particle trace solution can be saved to an external file and re-loaded through the Render Settings dialog box, under the menu item File. Select "Save Rendering Database" to save the solution to an external file ".ptd"  (e.g., "test_ies.ptd") for re-use later on. And select "Load Rendering Database" to reuse the solution saved.  Note that you can also "Save Rendering Solution to Dgn" to store the particle trace data file internally to the drawing file, but this tends to increase the size of the drawing file to an unproductive size. Saving to an external file is the best option.

• The Query Illumination tool  (Q4) can be used to test luminance levels for varied surfaces.
  
  
  
  
• Phillips Lighting web site with current IES data files:  http://www.colorkinetics.com/support/ies/
• Selected and older lighting manufacturer data, see IES Data Samples  (this is from an older lighting catalog)  

10.  PARTICLE TRACING - OVERALL CONCEPTS/FAQ EXCERPTED FROM BENTLEY'S MATERIALS

Question: How do I get a "good" particle Trace solution?

Answer : There are several different ways to achieve better results when we Particle Trace render. Below are a few ways to accomplish this:

STEP 1: Raytrace

• First thing to do is open the rendering tools, and render the scene using Raytrace to see what the scene looks like currently, but be sure to turn off ambient and flashbulb lighting. If the scene does not look good in Raytrace, then chances are it is not going to look good in a Particle Trace solution. It may be too dark, then we need to address the lighting by adding more natural light. If the scene is brighter than desired, then the lights need to lessen by lowering the intensity. So when the scene looks well lit and everything is in clear view.

STEP 2: Particle setup

• Use the default settings first, to see what you get.
• 1. million particles
• Mesh smoothness on 3
• Check off "RayTrace Final Display" so we can see the results faster.

STEP 3: Brightness

• The first rendering may appear darker than the Previous Raytrace rendering.
• This can be fixed by adjusting the brightness slider.

• There is tiling or faceted elements then more particles are needed (some edges can not be smoothed if the angle is too sharp).
• There are color blotches randomly in the scene.
• Try bumping it up to 5 million particles in the scene, but to do this efficiently, change the Action setting to "Add more particles and redo mesh" and set the particles to 4 million. Since there is already 1 million particles in the scene, adding 4 million more will give an even total of 5 million.
• It may look better, but it may not look good enough. Adding more particles is the best way to get the scene more convincingly rendered and more completely realized with respect to the distribution of light energy.
• If some elements do not smooth out then they probably will never smooth out enough. This is related to how the element was modeled.
• If the angles of the edges are too sharp they will be able to be smoothed out. However, at a certain point, pushing smoothing too far  is like trying to smooth out a cube. You may simply have realized the best rendering possible beyond which refinements will be feasible.

STEP 5: Mesh smoothing

• To change the mesh settings, which will create more detail, first you need to click the Redo Mesh button, since you are not adding particles; you do not need to recalculate the shooting of the particles.
• Setting the smoothness setting to a lower value such as 1, the rendering, will be less detailed and the particles will spaced further apart, which can produce the colored spots. This is because the mesh is not as detailed and will not except as many particles; hence the colors become blotchy.
• The default setting of 3 may be good enough.

STEP 6: Final touches

• Once you are satisfied with the detail of the solution you can display the final rendering for the view by going to the Particle Trace settings and selecting "Ray Trace Final Display"
• Then select "Redisplay Solution and select the view to render the scene for a final rendering.
• The final rendering combines the Particle Trace solution with a Raytrace rendering. The Particle Trace solution is not a rendering solution on its own. It is only a lighting solution.
• Raytracing the scene will display the highlights and reflections of the elements in the scene.

ADDITIONAL  DOCUMENTATION:

http://archweb.arch.virginia.edu//arch541/Handouts/sample.htm {sample marble