freddyc

I have been trying to get my head around the jit.expr object.

https://cycling74.com/tutorials/demystifying-expressions-in-jitter/

 and now I am trying to understand how the jit.expr object works on this physics recipe (attached) but I can't get my head around it. Anyone care to enlighten me ?

I went through this tutorial https://cycling74.com/tutorials/demystifying-expressions-in-jitter/ and now I am trying to understand how the jit.expr object works on this physics recipe (attached) but I can't get my head around it. Anyone care to enlighten me ?


jit-expr-enlightenment

I don't understand how the jit.expr is manipulating the parameters of the jit.phys.multiple object.

For example how does the 2nd plane of the first matrix (@expr in[0].p[1]*0.12+0.05 in[0].p[1]*0.12+0.05 0.) affect the position and scale of the jit.phys.multiple object that is connected to ?

I don't understand how the jit.expr is manipulating the parameters of the jit.phys.multiple object. 

For example how does the 2nd plane of the first matrix (@expr in[0].p[1]*0.12+0.05 in[0].p[1]*0.12+0.05 0.) affect the position and scale of the jit.phys.multiple object that is connected to ?


I am basically trying to understand the ForceSystem recipe by dissecting it and the only bit I am stuck is how the jit.expr objects are working on the jit.phys.multiple and jit.multiple objects.

The attribute @physparams is what defines the inlets of jit.multiple (in this case, the first two inlets are position and scale - and they each require input from a 3-plane matrix). See the reference docs.

jit.expr is grabbing values from a 4-plane matrix [jit.noise 4 float32 400] and processing them as a 3-plane matrix. The values are then sent to the 'position' and 'scale' inlets of [jit.multiple].

Not sure if this is the confusing part but... the way you define planes in jit.expr is with 

... Hence: [jit.expr @expr in[0].p[1]*0.12+0.05 in[0].p[1]*0.12+0.05 0.] defines three planes:

The attribute @physparams is what defines the inlets of jit.multiple (in this case, the first two inlets are position and scale - and they each require input from a 3-plane matrix).  See the reference docs.

jit.expr is grabbing values from a 4-plane matrix [jit.noise 4 float32 400] and processing them as a 3-plane matrix.  The values are then sent to the 'position' and 'scale' inlets of [jit.multiple]. 

Not sure if this is the confusing part but... the way you define planes in jit.expr is with spaces...   Hence:  [jit.expr @expr in[0].p[1]*0.12+0.05 in[0].p[1]*0.12+0.05 0.] defines three planes:

in[0].p[1]*0.12+0.05
in[0].p[1]*0.12+0.05
0.

the way you define planes in jit.expr is with spaces

Does this mean that we multiply the second plane by 0.12 and the adding 0.05 ?

I think I need to go back to maths school.

I understand everything besides this: the way you define planes in jit.expr is with spaces

in[0].p[1]*0.12+0.05
in[0].p[1]*0.12+0.05
0. 

Does this mean that we multiply the second plane by 0.12 and the adding 0.05 ? 

I think I need to go back to maths school.


yes, that's it. For each cell, the value of the first plane is multiplicated by 0.12, and 0.05 is added. The same operation is applied to valkue of second plane. Each value of third plane is replaced by 0.

 like positions in a list (p[0], p[1], p[2], p[3]).

 as if the expression itself was a list. That is to say, the first plane of the output is the first element of the 'list' of expressions. The second plane of the output is the second element of the 'list' of expressions, etc.

[jit.expr @expr subexpr1 subexpr2 subexpr3 subexpr4]

[jit.expr @expr OutputPlane1 OutputPlane2 OutputPlane3 OutputPlane4]

Also keep in mind that the use of quotes overrides the use of spaces. So if you have spaces enclosed in quotes, the spaces are ignored and everything enclosed in quotes defines the plane.

[jit.expr @expr “subexpr 1” “subexpr 2” “subexpr 3” “subexpr 4”]

[jit.expr @expr "Output Plane 1" "Output Plane 2" "Output Plane 3" "Output Plane 4"]

output plane 2: [jit.expr @expr in[0].p[1]*0.12+0.05 

output plane 3: [jit.expr @expr in[0].p[1]*0.12+0.05 in[0].p[1]0.12+0.05 

output plane 2: [jit.expr @expr “in[0].p[1] * 0.12 + 0.05” 

output plane 3: [jit.expr @expr “in[0].p[1] * 0.12 + 0.05” “in[0].p[1] * 0.12 + 0.05” 

jit.expr refers to the input like positions in a list (p[0], p[1], p[2], p[3]).

jit.expr defines the output as if the expression itself was a list.  That is to say, the first plane of the output is the first element of the 'list' of expressions.  The second plane of the output is the second element of the 'list' of expressions, etc.

Also keep in mind that the use of quotes overrides the use of spaces.  So if you have spaces enclosed in quotes, the spaces are ignored and everything enclosed in quotes defines the plane.

output plane 1: [jit.expr @expr in[0].p[1]*0.12+0.05 in[0].p[1]0.12+0.05 0.]
output plane 2: [jit.expr @expr in[0].p[1]*0.12+0.05 in[0].p[1]0.12+0.05 0.]
output plane 3: [jit.expr @expr in[0].p[1]*0.12+0.05 in[0].p[1]0.12+0.05 0.]

output plane 1: [jit.expr @expr ”in[0].p[1] * 0.12 + 0.05” “in[0].p[1]0.12+0.05” 0.]
output plane 2: [jit.expr @expr “in[0].p[1] * 0.12 + 0.05” ”in[0].p[1] * 0.12 + 0.05” 0.]
output plane 3: [jit.expr @expr “in[0].p[1] * 0.12 + 0.05” “in[0].p[1] * 0.12 + 0.05” 0.]


I understand how it works now. Thanks for this, much appreciated.

I'm trying to use jit.clip inside jit.expr.

Some I'm having troubles setting the 'min' and 'max' attributes inside jit.expr.

I'm trying to use jit.clip inside jit.expr.
Some I'm having troubles setting the 'min' and 'max' attributes inside jit.expr.
I can not get my head around it... :/
Please see the patch bellow.



I'm trying to use jit.clip inside jit.expr, but I'm having troubles settings the 'min' and 'max' attributes of jit.clip.

So, the question how to set properly multiple attributes inside a expression?

Hello to All,
I'm trying to use jit.clip inside jit.expr, but I'm having troubles settings the 'min' and 'max' attributes of jit.clip.
I can not get my head around it...
So, the question how to set properly multiple attributes inside a expression?
See the patch bellow.


Nearly ten years later this is right on the button.

jit.expr enlightenment