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Difference between Local Ray Tracing and Ray Tracing Impacts
PostPosted: Tue Aug 30, 2016 4:05 pm Reply with quote
dmar
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Joined: 30 Jun 2016
Posts: 2




Hello,
I'm doing a university project in which i evaluate the RT of a very simple shape form with even absorption with the different methods of Ease.

In Local Ray Tracing method you can choose either Image Source Method or Ray tracing Impact method, so, if i select the last one, is it the same as if i would use the Ray Tracing Impacts routine? I've used both and i get very similar or almost same RT's. Perhaps the simulation time is a bit longer (but almost unnoticeable).

Could you explain me if there's any difference in terms of ray detection or algorithm? About "Ray tracing Impacts" it is said in Ease's manual that registers rays which hits a receptor within 1 meter ballon and then, starts an image source routine. But in Local Ray Tracing the manual doesn't tell anything about the procedure.

Thank you,
Regards.
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PostPosted: Wed Aug 31, 2016 3:11 pm Reply with quote
AFMG Pedro Lima
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Joined: 05 Jun 2010
Posts: 266
Location: Germany




Dear dmar,

The differences between Local Ray Tracing and Ray Tracing / Mirror Image Impacts are purely functional. Local Ray Tracing feature can use both algorithms: Ray Tracing Impacts and Mirror Image Impacts (as you noticed). The difference is on what the user would like to do/see. Below I have quickly summarized the key aspects on theses routines here (except for AURA):

LOCAL RAY TRACING
* For quick local analysis via Probe or Ears modules
* Reflectogram at a single (selected) position only
* It will not display the rays propagation paths in the View Project module
* Access through:
* Area/Room Mapping: at walker positions
* Ray Tracing module: at a selected seat
* Algorithms: Mirror Image Impacts or Ray Tracing Impacts

RAY TRACING IMPACTS
* For detailed acoustical investigations and EARS auralizations
* Calculation at several positions (in a single shot)
* Displays info and propagation path for each ray in the View Project window
* Access only through Ray Tracing module
* Ray Tracing Impacts algorithm: Registers rays that pass within a meter of the chosen point (1 meter counting balloon). Stores results and automatically runs a mirror image routine to identify the impact that hit the center of the counting balloon.
* Usually a large number of rays is used: >100.000 (uses a statistical approach to detect the reflections that hit a seat - fits in the Monte Carlo methods)
* Computational time is proportional to the number of Faces
* Rule of thumb for the Order selection: MFP * Order = (approx.) Time Frame
* Produces impact files that used to generate reflectograms

MIRROR IMAGE IMPACTS
* Mirror image method: will calculate ALL possible reflections for a selected Order Number - leaves nothing to chance (it is not a statistical approach)
* Calculations take longer for higher orders of reflection and high number of Faces
* Not recommended for rooms with more than 40 Faces or with reflections order > 10. But itīs quite faster than the statistical Ray Tracing for lower orders.
* Produces impact files - used to generate reflectograms
* Rule of thumb for the order selection: MFP * Order = (approx.) Time Frame

Other than the manual, have you noticed EASEīs comprehensive tutorial? http://ease.afmg.eu/index.php/documents.html

Kind Regards,
Pedro
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PostPosted: Wed Oct 05, 2016 9:59 pm Reply with quote
dmar
Member
 
Joined: 30 Jun 2016
Posts: 2




Thank you Pedro, I had not seen your answer till now.

Then, The Ray Tracing Impacts routine that can be selected from "Local Ray Tracing" option is the same as The "Ray Tracing Impacts" option itself?

Through "Local Ray Tracing" -> Ray Tracing Impacts selection, is also run the mirror image routine to detect impact at the center? or it's only valid for the "Ray Tracing Impacts" option?

I've noticed as well that by selecting "Ray Tracing Impacts" directly, i get two windows for options: one says "Find Impacts" and then a "Ray Tracing" window. It seems to be the two parts of the algorithm you mentioned (one from simple Ray Tracing, and Find Impacts for the Image Routine). Is this right? and why through "Local Ray Tracing"->Ray tracing Impacts there isn't the "Find impacts" option window if the algorithm is the same?

I hope you can explain me that. Basically if there's any difference between "Local Ray Tracing"->Ray Tracing Impacts and the direct "Ray Tracing Impacts" option.

Thank you very much for your help.

Regards,

Dani
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PostPosted: Tue Oct 11, 2016 4:22 pm Reply with quote
AFMG Pedro Lima
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Joined: 05 Jun 2010
Posts: 266
Location: Germany




Hi Dani,

"Then, The Ray Tracing Impacts routine that can be selected from "Local Ray Tracing" option is the same as The "Ray Tracing Impacts" option itself?"

Yes, the algorithm to find the impacts is the same for both. Only the functionality changes, i.e. what you can do with the results and which results and calculated and displayed. For instance, in Local Ray Tracing you can Pick the walker location, the propagation path is not displayed (or calculated) and a response file can be directly created and sent to Probe. Whereas in Ray Tracing Impacts, you have the whole information, including the trace and impact files.

"Through "Local Ray Tracing" -> Ray Tracing Impacts selection, is also run the mirror image routine to detect impact at the center? or it's only valid for the "Ray Tracing Impacts" option"

Yes. The Ray Tracing routine is used to determine the paths to the listener. These are then traced back to the speaker by mirror image.

"I've noticed as well that by selecting "Ray Tracing Impacts" directly, i get two windows for options: one says "Find Impacts" and then a "Ray Tracing" window. It seems to be the two parts of the algorithm you mentioned (one from simple Ray Tracing, and Find Impacts for the Image Routine). Is this right?"

Excatly.

"...and why through "Local Ray Tracing"->Ray tracing Impacts there isn't the "Find impacts" option window if the algorithm is the same? "

As told above, they have different funcionality. Here a response file (.rsp) is directly created, so it can be slightly faster to calculate. Below a quick view on the characteristics of the different files.

Trace files *.TRC
* From rays that are sent in all directions
* For general reflections pattern studies from a sound source
* No specific observation point (no Listener Seat)
* Stores paths, faces intersected, energy loss

Impact files *.MPC
* From rays that are sent in all directions
* Keeps only the information for rays that hit a selected Listener Seat
* Stores paths, faces intersected, energy loss
* Can be computed from *.TRC file

Response files *.RSP
*Stores amplitude, time, phase, direction
*Discards path and face intersections
*View in Probe, transform for auralization

HTH,
Pedro
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