[Info] Ambient Occlusion -> Simple Rays

Wacov

This is really amazing. I mean, if you could do the raytesting separately with a faster language, it'd be really useful.

thomthom

The .raytest method is running in SU's C. Not calculated using Ruby. Ruby just calls the C method.

qpik

Does that mean that model.raytest algorithm is inherently slow?
So I would need to write my own in C.

thomthom

What I meant was that the .raytest is probably written in C already.

Jim

Yeah, to make it faster wouldn't you need to export the geometry so an external routine could both loop and perform the raytest?

qpik

But I would have to export geometry for that one external routine.
Is there other way?

@thomthom said:

What I meant was that the .raytest is probably written in C already.

I've got that, I just wonder what makes it slow then and how to write a faster one.

I guess I have to prepare myself for switching to C. Even for my simple use, which is lately sunlight exposure analysis, it's simply too slow, when run on part of the city centre model.

Kuba

ps. Many thanks for all the help so far.

Wacov

@thomthom said:

The .raytest method is running in SU's C. Not calculated using Ruby. Ruby just calls the C method.

Ok.

I guess I don't know what I'm talking about, but doesn't SU's raytest method extract more information than you need for your plugin? Maybe that's why it's so (comparatively) slow.

thomthom

Possibly. I guess it depends on what you need it for.

qpik

@wacov said:

I guess I don't know what I'm talking about, but doesn't SU's raytest method extract more information than you need for your plugin? Maybe that's why it's so (comparatively) slow.

I thought exactly the same, as it returns "the first thing that the ray hits". I suppose it means "the closest thing". For my purpose it's enough to get first-on-the-list hit end exit.
That might do the trick.

qpik

I quickly wrote this, but it worked MUCH slower than original method.

def raytest2 ray
 hit = false
 entities = self.entities
 entities.each { |face|
   if face.kind_of?(Sketchup;;Face) and face.classify_point(ray[0]) > 4
    plane = [face.vertices[0].position, face.normal]
    intersection = Geom.intersect_line_plane(ray, plane)
    if intersection and face.classify_point(intersection) < 8
     hit = true
     break
   end
  end
 }
 return hit
end

This could be optimized by passing pre-sorted face array (based on results from previous tests) instead of browsing entities array, but I doubt it would speed it up much.
What do you think?

thomthom

@qpik said:

plane = [face.vertices[0].position, face.normal]

You can use face.plane instead

@qpik said:

This could be optimized by passing pre-sorted face array (based on results from previous tests) instead of browsing entities array, but I doubt it would speed it up much.
What do you think?

hmm... If you only iterate the entities collection once then it won't help to pre-process to filter out only faces. Infact, that would mean more iterations. But if you need to iterate the face multiple times, then you will save time on pre-filtering.

@qpik said:

I thought exactly the same, as it returns "the first thing that the ray hits". I suppose it means "the closest thing". For my purpose it's enough to get first-on-the-list hit end exit.

Isn't that the same thing?

@qpik said:

I quickly wrote this, but it worked MUCH slower than original method.

You're writing a ruby method to be faster than a C method - that C method must be doing a lot of extra processing in order to be able to out-perform it in Ruby.

qpik

@thomthom said:

You can use face.plane instead

Somehow I didn't notice that one in the API

@thomthom said:

hmm... If you only iterate the entities collection once then it won't help to pre-process to filter out only faces. Infact, that would mean more iterations. But if you need to iterate the face multiple times, then you will save time on pre-filtering.

I meant to sort the collection before proceeding to the next testing point. The faces that got hit before might as well be the first to get hit by rays cast from adjacent point.

@thomthom said:

@qpik said:

I thought exactly the same, as it returns "the first thing that the ray hits". I suppose it means "the closest thing". For my purpose it's enough to get first-on-the-list hit end exit.

Isn't that the same thing?

I suppose model.raytest doesn't break after first positive ray hit, but returns the closest one from an array of all.

@thomthom said:

@qpik said:

I quickly wrote this, but it worked MUCH slower than original method.

You're writing a ruby method to be faster than a C method - that C method must be doing a lot of extra processing in order to be able to out-perform it in Ruby.

That is certainly true. That is why I managed to connect with a DLL using Win32api.call (BTW thanks to TBD for his SUDLL example).
Now I'm on my way to moving everything to C. I hope this will finally give a speed boost.

I'm looking into Ruby-OpenGL as well for another approach.
Here is an example - http://forums.sketchucation.com/viewtopic.php?f=180&t=20893&p=209966#p209966

thomthom

@qpik said:

I suppose model.raytest doesn't break after first positive ray hit, but returns the closest one from an array of all.

that would be very odd. if it did produce a full array before returning I think it should return the full array.

qpik

But then how would it find out the closest intersection?

ps. I write all this out of my head, I'm not familiar with 3d algorithms.

tomasz

@qpik said:

I suppose model.raytest doesn't break after first positive ray hit, but returns the closest one from an array of all.

I think it does break after first positive hit. Make sure you check if the object is not hidden or on a hidden layer, otherwise your rays will stop too early when hidden layer present in a model.

qpik

Yeah, but how would the method know if the first hit is the closest?
It could be for example some distant face that got hit first, because it was first in the collection.

thomthom

Did you ever find any improvements that could be made?

qpik

I planned writing new method in C and calling it via Win32api... but I never find time and enough determination to do it. I wish somebody else did it instead , someone who knows C, unlike me.

thomthom

I'm also an C ignorant...

KiraNL

Any chance this ever might come out which works for round shapes?
Love to use this as subtile shadows over the textures, sort of lighting baking.

[Info] Ambient Occlusion -&gt; Simple Rays

[Info] Ambient Occlusion -> Simple Rays