Is there any way to creat laser scanner like point coulds from vray renders?

[YAPI_HAN_MIMARLIK]

Hi,

Recently I have been working on automating the process of blind spot analyzes in construction projects. In construction projects in order to analyze blind spot of equipment we execute 3D laser scaners. Then areas which are not visible to laser camera are identified as a point cloud. Is there any way to achieve that with vray?
vray irradiance map is some how so close to what I want. But unfortunately there are only visible from irradiance map viewer!
Then I have found vraysamplerinfo. nuke guys using this with RGB channel combination to create point cloud in nuke. But I don't know if there is any possibility to do the same in 3Ds Max!
I need to found a way to calculate blind spot percentage in order to complete my master thesis in construction management! I would really appreciated if any one could help me with this challenge.

Thanks

[joconnell]

What's the final result you'd like to end up with? And how is the blind spot percentage calculated normally? It's very easy to make something that looks like a simple point cloud in max from a single view, but how do you calculate the percentage of not seen parts? Is it based on volume? Or surface?

[YAPI_HAN_MIMARLIK]

The result is something similar to this:

the best way is to calculate as volume and calculate volume of each blind spite separately. then ratio of blind spot will be calculate as below:
total volume of blind spots / volume of semi-sphere


if volume base calculation is not achievable we could simply calculate area of dark areas on test circle which is ground lvl.

here is a screen shot of my elementary test scene. this would be replaced with construction heavy vehicles and site model.

[joconnell]

Hmm - I'm thinking there might be a way to do this with particles and a volume select. It'll give you a way of keeping the seen parts and hiding the unseen parts and vice versa, but it won't give you a percentage of one versus the other. It'll be based on having a fairly dense mesh too.

[YAPI_HAN_MIMARLIK]

I can manage ratio calculating part manually. Could you please guide me with this particles and mesh select idea?
Thanks

[joconnell]

Okay. So of you use particle flow, you can stick an emitter in the middle spot that you were using for your camera. Set it to emit particles from the pivot out so they spray 360 degrees. Ideally for your own convenience if you have your objects to test as one single collapsed mesh, put in a collision operator in pflow. For all the particles that collide, make them stop when they hit your target mesh. This should be almost similar to photons of light hitting the geometry and missing all the other surfaces that they can't see - similar to the light rays above.

Next collapse the pflow mesh. For this you'll have to go to compound objects > Mesher. Make this at 0,0,0 in the viewports or move it there. Pick your pflow and it'll make a copy of it as a mesh that you can collapse. Once you have a dumb mesh of your particles, and a dumb mesh of your object you're testing for view, put a volume select modifier on the object. Set the selection type to object, and pick your mesher collapsed particles. If you set your selection type to face, all the places where the particles have hit your mesh will be selected. If you put on a delete mesh modifier after this, you'll delete all the mesh parts that have been "seen" and leave you with only the unseen parts.

[YAPI_HAN_MIMARLIK]

excellent thanks for your help. I will test it tomorrow at office and inform you the results.
best wishes

[YAPI_HAN_MIMARLIK]

Dear joconnell,
Today I did some test and achieve some points that I want to share them with you. first of all I wanna share some photos of my test scene.

first of all as you may notice I have problem with particle positions. despite shooting from front some of them stick on back of teapot.
then the vol select mode give me some strange results. as you see it doesn't select all the faces which interact with mesher. I checked if they aren't on the surface but they are and no visual problem. :P
the other problem is particles are too heavy to handle. here I have on 20k but my machine has some difficulties in handling. my pc is i7 990x and 24gb ram gtx 580.

what do you think?

however render based particles are so easy to handle! here is what I mean: https://vimeo.com/11074371
In this method I just need nuke to convert renders to point cloud then as far as I know nuke 6.2 has the ability to export point cloud. what do you think about this method?

[joconnell]

Might be a case of using bigger particle shapes or making the faces of the collision object smaller? The nuke method will work fine alright, I was just trying to think of what would give you something you can count at the end to figure out the percentage. What format do you need the point cloud saved as?

[YAPI_HAN_MIMARLIK]

I don't know what is the problem and still I haven't managed any solution! You know it seems impossible to calculate the percentage or ratio automatically and I'm thinking of handling it manually. for point cloud I think PTS or CSV would be fine. I tried that nuke method but my points become flat on the line! I don't know where was my mistake everything seems normal. this is so far I achieved.

[vlado]

I tried that nuke method but my points become flat on the line! I don't know where was my mistake everything seems normal.

What file format are you saving your world-point pass in? You need 32-bit OpenEXR file to get proper results; other formats (like PNG or JPG) will clamp the output.

Best regards,
Vlado

[YAPI_HAN_MIMARLIK]

Dear Vlado here is what I have done so far:
establishing simple scene with vray
adding vrayextratex to render elements and linking this extratex to vraysamplerinfo:

hitting render and saving it in exr format:

importing both rgb and extratex channel in nuke 6.2 and merge them with PositionsToPoints. and here is the result:

even tried to shuffle blue and red channel:

but no success. how ever the files from pixel factory works great: http://www.pxfactory.eu/plug/PointCloud/pointCloud.html
I would appreciate if someone could help me.

[YAPI_HAN_MIMARLIK]

any suggestion?

[YoyoBoy]

Why not just put a shadow-casting Omni Light inside, render a separate pass with it, and comp?

[YoyoBoy]

Oh, nevermind. I misunderstood what you were saying.