Julien Bayle

Pointed there by Robert R., i'm trying to implement view-frustum culling into my system.

http://www.lighthouse3d.com/tutorials/view-frustum-culling/

 which seems to be a great reference (I saw this link a bit everywhere)

I'm currently into the Geometric Approach and, for sure, I need some generous hands to help me.

http://www.lighthouse3d.com/tutorials/view-frustum-culling/geometric-approach-extracting-the-planes/

Implementation is a bit more tricky (for me)

http://www.lighthouse3d.com/tutorials/view-frustum-culling/geometric-approach-implementation/

As attached, I'm okay (I guess) with the setCamInternals.

I'm stuck in implementing the setCamDef which has to compute 3 vectors and to render the 8 points of the frustum (=the 6 planes used for checking which object has to be sent to the openGL pipeline)

I'm stuck because I don't know how to grab those 3 vectors required.

The first one is ok, this is the position of the cam.

The second one is "a point to where the camera is pointing" ... How can I find/calculate it ?

The third is the up vector, same .. . how can I grab it ??

Pointed there by Robert R., i'm trying to implement view-frustum culling into my system.
I'm using : http://www.lighthouse3d.com/tutorials/view-frustum-culling/ which seems to be a great reference (I saw this link a bit everywhere)

I understood the demo there : http://www.lighthouse3d.com/tutorials/view-frustum-culling/geometric-approach-extracting-the-planes/
This is the global description.

Implementation is a bit more tricky (for me)
http://www.lighthouse3d.com/tutorials/view-frustum-culling/geometric-approach-implementation/

The first one is ok, this is the position of the cam.
The second one is "a point to where the camera is pointing" ... How can I find/calculate it ?
The third is the up vector, same .. . how can I grab it ??

view-frustum-culling-implementation-with-jit-gen-matrices

"The second one is "a point to where the camera is pointing" ... How can I find/calculate it ?

The third is the up vector, same .. . how can I grab it ??"

both of these attributes can be retrieved.

you have to attach a jit.anim.node to your jit.gl.camera in order to make it work. (this requirement will be removed in an upcoming release)

the camera-point-position is the @lookat attribute of jit.anim.node.

the up vector can be calculated from the anim.node's @quat attribute, by sending it to a jit.quat object, and querrying the yaxis attribute. (the up vector is the Y axis transformed by the camera's current quaternion)

"The second one is "a point to where the camera is pointing" ... How can I find/calculate it ?
The third is the up vector, same .. . how can I grab it ??"

both of these attributes can be retrieved.
you have to attach a jit.anim.node to your jit.gl.camera in order to make it work. (this requirement will be removed in an upcoming release)

I even understood how jit.anim.node object worked :)

implementing my calculation about view-frustum culling in next hours and posting here the result!!

Hi Robert,
a big thanks to you.
I even understood how jit.anim.node object worked :)

implementing my calculation about view-frustum culling in next hours and posting here the result!!


I finally have little problem to retrieve ratio parameter :-/ (in setCamInternals : 

http://www.lighthouse3d.com/tutorials/view-frustum-culling/geometric-approach-implementation/)

I guess it is the ratio between height and wide of frustum?!

I finally have little problem to retrieve ratio parameter :-/ (in setCamInternals : http://www.lighthouse3d.com/tutorials/view-frustum-culling/geometric-approach-implementation/)

I guess it is the ratio between height and wide of frustum?!


so, I have some difficulties about 2 things:

- to retrieve the ratio parameter in order to calculate my 8 points defining my 6 planes for the culling

basically, here is my current implementation on jit.gen

ratio & planes implementation are missing, and of course, the objects matching test.

probably, I'll create a matrix with my 8 points, then another jit.gen which would be fed by objects positions matrix + my 8 points matrix, calculating which objects is in or out of scope...

would you help me with that Robert, or Wes or ?

so, I have some difficulties about 2 things:
- to retrieve the ratio parameter in order to calculate my 8 points defining my 6 planes for the culling
- to put that into my jit.gen.

basically, here is my current implementation on jit.gen
ratio & planes implementation are missing, and of course, the objects matching test.

ratio is window-width divided by window-height.

a month ago I solved the modelviewprojection transformation with a max patch:

https://cycling74.com/forums/how-to-create-a-modelviewprojection-matrix-with-jit-anim-nodes

this patch calculates the xy-pos on the screen for one vertice. maybe it could be used to do what you wanna achieve?

@Robert.. thanks for this obvious thing I didn't even notice :-/

I don't know how to apply your nice patch (which I understood btw) to my "case"

http://www.lighthouse3d.com/tutorials/view-frustum-culling/geometric-approach-implementation

@maybites: thanks a lot for your link.
I don't know how to apply your nice patch (which I understood btw) to my "case"
I'm trying to implement http://www.lighthouse3d.com/tutorials/view-frustum-culling/geometric-approach-implementation


if I sent an n planes matrix to a jit.gen, what is the rule to retrieve a particular plane ??

I'm currently sending an 1x1 matrix with 4 planes to the first inlet of my jit.gen

I'm mapping the in 1 to a codebox, on the first inlet too

I'm currently sending an 1x1 matrix with 4 planes to the first inlet of my jit.gen
I'm mapping the in 1 to a codebox, on the first inlet too
so in1.x, .y, .z are the first 3 planes

I have that huge jit.gen (finally not that big)

- a point on the view direction of the cam (lookat)

it processes the whole parameters to render the 8 points of the view frustum.

I need to normalize a vector inside the codebox.

I did the basic calculation including sqrt()

does it exist a better way inside GenExpr / codebox ?

Now, I have my eight point defining my view.

I have to "test" all my object according to those planes in order to have a list of objects I have to inactivate and activate, according to the position & orientation of my cam.

That part is done in the second codebox and has to be done for the 6 planes.

Knowing I have a matrix with all my objects' positions, how can I test each one against those 6 planes ??

I don't know if this is the best implementation I could make of that concept.

I have that huge jit.gen (finally not that big)
It takes some parameters as input:
- position of the cam
- a point on the view direction of the cam (lookat)
- the up vector

It takes also cam parameters like:
- lens angle
- ratio of the view (w/h)
- nearClip distance
- farClip distance

it processes the whole parameters to render the 8 points of the view frustum.
As shown there: http://www.lighthouse3d.com/tutorials/view-frustum-culling/geometric-approach-extracting-the-planes/

The calculation is there:
http://www.lighthouse3d.com/tutorials/view-frustum-culling/geometric-approach-implementation/

first question:
I need to normalize a vector inside the codebox.
I did the basic calculation including sqrt()
does it exist a better way inside GenExpr / codebox ?

Now, I have my eight point defining my view.
They defines my 6 planes too.

any help would be appreciate.
I don't know if this is the best implementation I could make of that concept.

Only to clarify my approach (which is quick and dirty compare to the road you are taking).

As far as I understand you wanna have a tool that tells you if your object is inside the viewing frustum. my patch does that insofar, that it calculates the x-y screen-coordinates of a 3d vertex. if the x-y coordinates are not inside the screen, the vertex would be outside the frustum.

But I might have missunderstood your problem.

x,y aren't enough because my cam doesn't have to be locked in only one plane.

hi there,
x,y aren't enough because my cam doesn't have to be locked in only one plane.


if I understand you correctly: my patch works with all sorts of camera-transformations.

I'm currently trying to make a calculation for all objects around the cam for pure sound purpose. I already need that.

The position of the object relatively to the cam would be defined by azimuth/elevation/distance.

Then, I'd like to make a one pass calculation and calculate if the object has to be activated or not according to azimuth/elevation.

Indeed, all in one could be nice & efficient.

I'm currently trying to make a calculation for all objects around the cam for pure sound purpose. I already need that.
The position of the object relatively to the cam would be defined by azimuth/elevation/distance.

Indeed, all in one could be nice & efficient.


view-frustum culling implementation with jit.gen & matrices