Simulating optical detectors

[heavenly]

Greetings everybody.

There is a challenge for you experts in computer graphics.

I am doing a project now regarding simulating optical detectors, like cameras.

For example in a room, we want to place these cameras around trying to cover as much as possible of the room.

I am wondering, what kind of lighting technology in computer graphics I will have to use to make this as easy as possible.

I have come across a software simulating lamps in a room, and show how it will illuminate the environment in 3D. It is kind of similar of what I want to do with my project, although technically it's the opposite. Both a lamp and an optical detector have a field-of-view (or cone), which means they have a certain angle vertically and horizonally that they will spread the light out, or can detect, repsectively. This software is using a radiosity engine to simulate the lighting, which has all these reflections of light, showing lux curves and lux values.

Radiosity is a global illumination technique, and that is not what i need. I only need a simple lighting technique or something else, just to simulate what the optical detectors can see, or cannot see.

What simple techniques could I apply on this software instead of radiosity, which is an overkill. I don't need to have any reflections at all. I just need something very simple that is easy to implement.

I hope some of you can give me some tips on this.

 

[Davros]

how about a point light

 

[imsabbel]

Greetings everybody.

There is a challenge for you experts in computer graphics.

I am doing a project now regarding simulating optical detectors, like cameras..

Take a look at indigorenderer.com
The newest versions support camera models and types, including diffraction artefacts on the aperture.

 

[heavenly]

Take a look at indigorenderer.com
The newest versions support camera models and types, including diffraction artefacts on the aperture.

Hi imsabbel.

Thanks for your tip.

I'm not actually looking for simulation of exposure time, focal distance, lens flair or such for the camera.

I want to be placing several flame detectors around an environment, and simulate what they can be able to detect, what is visible for them. So it works kind of like cameras, only that they can only see to a certain distance.

What software or technique could I use for that?

 

[heavenly]

Take a look at indigorenderer.com
The newest versions support camera models and types, including diffraction artefacts on the aperture.

Thanks imsabbel.

I think I didn't explained good enough on my first post.

I was just trying to set parallel between an optical flame detector and a camera, because the principle is the same.

Indigo seems only to be a renderer, and when it comes to camera simulation, in this program, you can change parameters to get several camera effects projected to your screen. And that is not quite what I'm looking for.

What i wish, is to simulate what several optical flame detectors placed around an environment can see, and where they cannot detect any possible flames. It is kind of like placing some spotlights and see where the lights will hit directly. So it is not about simulating exposure time, focal distance, lens flair etc.

How could this be done with OpenGL?

 

[Arun]

The URL in the post you were quoting was causing you to hit the spam detector, I just approved your posts now, don't worry (two of the three were slightly different so I kept both)

 

[PellePlutt]

It seems to me like you just want to simulate square spotlights (or regular ones? you mentioned a cone for field-of-view..), only not having brightness decrease with distance. Having shadows would be useful as well, I guess (seems like simple shadow-maps would be an obvious choice).
Either way, it seems pretty straight-forward.

 

[heavenly]

I know it seems very straigt-forward from a conceptual point of view. I just don't have much knowledge with lighting in OpenGL, and how it will be done specifically, and how to program it.

As for square or regular spotligths, I'm actually not quite sure. Both detectors use polar diagrams to show their range. And there are many different kind of optical flame detectors. For flame detectors that I have come across, they have polar diagram for vertical view and horizontal view, based on that, it seems like an elliptical view. I don't know exactly, because these diagrams are in 2D. Based on that it could have been rectangular view too, i guess.

For the records, typically flame detectors use ultraviolet light, infrared light, or a combination of these to detect flames.

I read about visibility determination for determing what to be drawn e.g in games to only draw what is visible, don't know if this could be applied to my problem, and how?

 

[PellePlutt]

My assumption was that you wanted to render some environment with several of these detectors, and then somehow show what areas are visible by detectors. In that case, you would definately want to model them in a very similar way to spotlights, and it should be fairly straightforward to find some tutorials on that.

If what you want to do is somehow render the entire scene from the point of view of one detector, that might be more complicated depending on exactly how they work.

 

[Davros]

heres how my little brain would try and do it
create your room in unreal ed
then add a point light - you use whatever is lit up to simulate the area the camera could see
then add more lights untill the whole room is lit up

 

[heavenly]

My assumption was that you wanted to render some environment with several of these detectors, and then somehow show what areas are visible by detectors. In that case, you would definately want to model them in a very similar way to spotlights, and it should be fairly straightforward to find some tutorials on that.

If what you want to do is somehow render the entire scene from the point of view of one detector, that might be more complicated depending on exactly how they work.

It is like your first assumption I want it to be, Pelle. To show what is visible for the detectors.

It is important to note that the camera example was just an analogy, what I'm dealing with is optical flame detectors, they can utilize ultraviolet light, infrared light, combination of both, or triple infrared. And they have limited distance range for a given flame size.

The field-of-view (terminology used for detectors) for a given flame detector is usually illustrated by polar diagrams for vertical and horizonal view, 2D-diagrams. Lamps use similar diagrams, usually with only one diagram for one point of view, I think, to describe the light distribution pattern.

I haven't found any tutorials on the net yet, that's partly why I'm on this forum.

 

[heavenly]

heres how my little brain would try and do it
create your room in unreal ed
then add a point light - you use whatever is lit up to simulate the area the camera could see
then add more lights untill the whole room is lit up

I'm not sure why you propose using a point light. Doesn't a point light have at least 180 degrees of light distribution? Could you please enlighten me.

Btw, is UnrealEd free downloadable?

 

[Davros]

i though a camera (what i thought you were trying to simulate) had the same light distribution as a point light - maybe it doesnt

ps: unrealed comes with any unreal game im not sure if it comes with the demo

you can place lights anywhere and also edit their properties

 

[imsabbel]

It is like your first assumption I want it to be, Pelle. To show what is visible for the detectors.

It is important to note that the camera example was just an analogy, what I'm dealing with is optical flame detectors, they can utilize ultraviolet light, infrared light, combination of both, or triple infrared. And they have limited distance range for a given flame size.

The field-of-view (terminology used for detectors) for a given flame detector is usually illustrated by polar diagrams for vertical and horizonal view, 2D-diagrams. Lamps use similar diagrams, usually with only one diagram for one point of view, I think, to describe the light distribution pattern.

I haven't found any tutorials on the net yet, that's partly why I'm on this forum.

Ok. In that case, i suggest the following:
You detectors have a certain opening angle.
Use in each of their positions a spot light, with the given opening angle. Plus a hard cutoff (or soft, if you want) at the maximum detection range. (i know this is possible in povray and 3dsmax, so i guess i should be in any decent package).

Disable radiosity&ambient lighting, and now you should be able to see the dead zones as black spots.

 

[heavenly]

Ok. In that case, i suggest the following:
You detectors have a certain opening angle.
Use in each of their positions a spot light, with the given opening angle. Plus a hard cutoff (or soft, if you want) at the maximum detection range. (i know this is possible in povray and 3dsmax, so i guess i should be in any decent package).

Disable radiosity&ambient lighting, and now you should be able to see the dead zones as black spots.

Thanks for the tip about povray, imsabbel. I just tested it out and it was good.

However, as I am going to to use OpenGL, I am wondering how I can achieve the following:

-Make a completely sudden light attenuation in a given distance (along the line of sight). The reason for this is to illustrate the range of an optical flame detector.

-Also have no attenuation in the spotlight cone across the radius.

Btw, I have seen an example making use of shadow map, and I think that is what I want to have, only at the opposite side of the illuminated object, to illustrate the light beam from the spotlight. How do I do that?

Just ask me if something is unclear. Thanks for the help.

 

[heavenly]

I just want to make a clarification. What I meant was using shadow volumes, not shadow maps.

How can i use similar effect as shadow volumes, to simulate/illustrate light rays/beams?