Workshop 8 Notes
2 November 2004

Particle Tracing and Rendering

	Action: Use old, update, or generate new solution., save solution
	Particle Settings: # particles to use (1 mil)
	Maximum Bounces: # times bounce (100 avg)
	Illuminate Both Sides: sometimes surfaces may be non-illuminated (best to default this on)
	Raytrace Direct: will alleviate multiple shadows, saves time, not good idea to use this in general
	Meshing Settings Smoothness: breakdown of mesh to effect smooth surf – noise to smooth
	Min Mesh Setting: higher # improves perform at low resolution
	Display Mode: visual, luminance (outgoing),illuminance (incoming)
	Raytrace Final Display: render using raytracing.
	Brightness Overlay: aperature.

12. Try settings
Action: create new solution
Use 1 million particles
Max bounces: 1 million
Illuminate both side surfaces
Ray trace direct illumination (off)
Material Receives/Reflecrts light (always)
Meshing settings (Smoothness 3, Detail 3)
Min mesh spacing (off)
Display mode: visual/color
Raytrace final display (on)
Wiremesh overlay (off)
Brighness multiplier (as is)
RENDER

13. Change to illuminance
Action: Display current solution
RENDER.

14. Attach view pers2;
Change to visual display
Add sunlight on.
Action: Create new solution (or load existing solution ptrace2.ptd if time short)
Add sunlight on.
Brighness multiplier (.310?)

(make visible setting window for explanation.
RENDER

Zoom up and rre-render same solution.

15. If time:
Action: display current solution
Lower Brightness mulitpier: (0.16)
Sample hot spot – alt option.
Re-render

16. Add background image (doesn’t really effect energy solution)
Action: display current solution
Re-render

17. Save solution (ptd particle trace solution file)

18. Reload solution.

19. Download IES files and test as attached to point source light in new dgn file.

Download from classes/examples:
ptrace/test-ies.dgn
Use 75rries.ies {Lightolier/12” handing pendent/incandescent.
With two point source lights/ and 0755FR.IES and 0584FR.IES data sets for 12” pendentive and 12”pendentive with aluminum reflector - 150 Watt bulbs.
Load shp file … Do current particle trace solution or make new one.
Adapt to brightness as necessary

See also lamps.html in same directory.

In new dgn file, you would:
Create point source light with IES data from web site such as http://www.lightolier.com.
.
(See also http://www.lighting-inc.com/searchman.html,, http://www.hadcolighting.com)

Part II. Particle Tracing – overall concepts in detail (from documentation provided by Microstation)

Question 1: 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 they are 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. 1 million particles
2. Mesh smoothness on 3
3. Check off "RayTrace Final Display" so we can see the results faster.

To speed up the process is to check on "Raytrace Direct illumination" in the Particle Trace setting dialog box. With this setting checked on, the raytracer will compute the shadows from the light source, but not the reflected light.

* Step 3 - Brightness
The first rendering may appear darker than the Previous Raytrace rendering. This can be fixed by adjusting the brightness multiplier.

* Step 4 - AMP (Add More Particles)
Add more particles if:
1. There is tiling or faceted elements then more particles are needed. Some edges can not be smoothed if the angle is too sharp.
2. There is 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 looking better. 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 it will be able to be smoothed out. It is like trying to smooth out a cube. Thus this is the best it will get.

* 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. So 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 selecting "Redisplay Solution and select the view to render the scene for a final rendering. This will combine the Particle Trace solution with a Raytrace rendering. The Particle Trace solution is not a rendering solution on it own, it is only a lighting solution. Raytracing the scene will display the highlights and reflections of the elements in the scene. Not using "Ray Trace Final display" speed the time for the rendering process. This helps when you are only working on the Particle Tracing solution and not concerned with the display of the highlights and reflections.

IES Data: Manufacturers provide this data on spread and intensity of light that can be substituted for lighting setup parameters. Should be used on point source lights only.
Illumincating Engineering Society (formed in 1906) (IESNA/IES) – Included Honory member Thomas Edison.

Question 4: What settings values are recommended for the initial rendering?

Answer: Using the default settings is a good place to start, they are:

* 1 Million Particles
* Mesh settings/Smoothness of 3
* Uncheck "Ray Trace Final Display"
* Turn on "Ray Trace Direct Illumination" in the Raytrace settings

Part III: Notes on rendering setup (rendering:general)
shadow maps (see general ... leave off save shadow maps)

anti aliasing grid side (draw pixels and diagonal lines)
grid size
2 means 4 passes on a 2x2 grid
3 means 9 passes on a 9x9 grid

stroke tolerance - maximum deviation of curve geometry from
true pixel locations where all curves represented as polygons
how many edges in polygon

shadow tolerance - how close shadows are to cast shadows
prevents from objects casting shadows on themselves,
higher values means lower accuracy

shadow filter size - softness of shadows , higher value means
softter shadow (describes number of pixels to look at in the
shadow map) ... too large means no shadows, too small means
objects cast shadows that conceal themselves.