woffle6452

OpenGL clipping planes (within jit.gl.sketch) don't seem to be working on max 5 for me (on Dell Laptop, windows XP). This simple patch that uses them works fine on max 4.6, then the same patch doesn't clip on max 5. Have any of the command/parameter names changed? Patch as text is pasted below, but it is just feeding a "glclipplane 0 1. 1. 1. 0." to a jit.gl.sketch (which has received "glenable clip_plane0").

Hi everyone.
OpenGL clipping planes (within jit.gl.sketch) don't seem to be working on max 5 for me (on Dell Laptop, windows XP). This simple patch that uses them works fine on max 4.6, then the same patch doesn't clip on max 5. Have any of the command/parameter names changed? Patch as text is pasted below, but it is just feeding a "glclipplane 0 1. 1. 1. 0." to a jit.gl.sketch (which has received "glenable clip_plane0").

Any ideas greatly appreciated!
Thanks, Dan

gl-clip-planes-in-max-5

On Jan 14, 2009, at 2:59 PM, woffle6452 wrote:

> OpenGL clipping planes (within jit.gl.sketch) don't seem to be 

> working on max 5 for me (on Dell Laptop, windows XP). This simple 

> patch that uses them works fine on max 4.6, then the same patch 

> doesn't clip on max 5. Have any of the command/parameter names 

> changed? Patch as text is pasted below, but it is just feeding a 

> "glclipplane 0 1. 1. 1. 0." to a jit.gl.sketch (which has received 

As far as I can tell, this patch is a misuse of jit.gl.sketch in a 

variety of ways, and seeming to rely on some state bleed through.

1. the gl commands to jit.gl.sketch are *added* to a list. so your 

configuration for enabling, disabling, changing the clip plane in 

jit.gl.sketch are just being added. send jit.gl.sketch

2. jit.gl.sketch state is only supposed to affect elements drawn 

inside of jit.gl.sketch's command list (following the relevant 

commands). In old versions of jit.gl.sketch there were state bleed 

through issues, which have been fixed. This patch seems like it might 

expect this sort of state bleed through. It is highly discouraged to 

rely on this kind of behavior unless you are very much aware of how 

these objects and open gl works, but you can permit the state changes 

inside jit.gl.sketch to bleed through with the attribute @pushstate 0.

> OpenGL clipping planes (within jit.gl.sketch) don't seem to be  
> working on max 5 for me (on Dell Laptop, windows XP). This simple  
> patch that uses them works fine on max 4.6, then the same patch  
> doesn't clip on max 5. Have any of the command/parameter names  
> changed? Patch as text is pasted below, but it is just feeding a  
> "glclipplane 0 1. 1. 1. 0." to a jit.gl.sketch (which has received  
> "glenable clip_plane0").

As far as I can tell, this patch is a misuse of jit.gl.sketch in a  
variety of ways, and seeming to rely on some state bleed through.

1. the gl commands to jit.gl.sketch are *added* to a list. so your  
configuration for enabling, disabling, changing the clip plane in  
jit.gl.sketch are just being added. send jit.gl.sketch

2. jit.gl.sketch state is only supposed to affect elements drawn  
inside of jit.gl.sketch's command list (following the relevant  
commands). In old versions of jit.gl.sketch there were state bleed  
through issues, which have been fixed. This patch seems like it might  
expect this sort of state bleed through. It is highly discouraged to  
rely on this kind of behavior unless you are very much aware of how  
these objects and open gl works, but you can permit the state changes  
inside jit.gl.sketch to bleed through with the attribute @pushstate 0.

Thanks Joshua! You are of course correct, I was expecting the old state bleed through...

Perhaps someone can suggest a better way...

I am generating shapes with jit.gl.gridshape (many with one object, using "@automatic 0" and "matrixoutput 1"). I would like to set up a clipping plane that only clips _some_ of the shapes. For now, doing it all within jit.gl.sketch isn't really an option unfortunately.

The (inelegant!) workaround I previously had going involved a jit.gl.sketch with "automatic 0". Then for each frame, this occured in this order:

-"gldisable clip_plane0" to the jit.gl.sketch

-bang to a jit.gl.gridshape (automatic 0 and matrixoutput 1) that wouldn't get clipped

-"glenable clip_plane0" to the jit.gl.sketch

-bang to a different jit.gl.gridshape (also automatic 0 and matrixoutput 1) that would get clipped

And since this grows the sketch command list, just clearing that out every once in a while (or even every frame). Ugly! But it works. Anyone have a more elegant idea?

Perhaps someone can suggest a better way...
I am generating shapes with jit.gl.gridshape (many with one object, using "@automatic 0" and "matrixoutput 1"). I would like to set up a clipping plane that only clips _some_ of the shapes. For now, doing it all within jit.gl.sketch isn't really an option unfortunately. 

The (inelegant!) workaround I previously had going involved a jit.gl.sketch with "automatic 0". Then for each frame, this occured in this order:
-"erase" to jit.gl.render
-"gldisable clip_plane0" to the jit.gl.sketch
-bang to jit.gl.sketch
-bang to a jit.gl.gridshape (automatic 0 and matrixoutput 1) that wouldn't get clipped
-"glenable clip_plane0" to the jit.gl.sketch
-bang to jit.gl.sketch
-bang to a different jit.gl.gridshape (also automatic 0 and matrixoutput 1) that would get clipped
-bang to jit.gl.render

And since this grows the sketch command list, just clearing that out every once in a while (or even every frame). Ugly! But it works. Anyone have a more elegant idea? 

GL clip planes in max 5?