jonathanharvey@dsl.pipex.com

I am looking to control an OpenGL object such as a square or circle using two numerical inputs.

1. A number between -5 and 5. This determines Speed at which the object is moving and if it is moving backwards or forwards.

2. A number between 0 and 360. This dictates the angle of the relative to the screen. 0 being vertically up.

In other words, lets say the first was a value of 2 and the second input was a value of 45, the object would be moving across the screen, forwards, at a fairly low speed and would be traveling up at an angle of 45 degrees (assume 0 degrees is vertically up). If the first input moved to a value of 5 then the speed at which it moved in that direction would be much faster. If we changed the second input, the object will steer round and head in the corresponding direction.

1. A number between -5 and 5.  This determines Speed at which the object is moving and if it is moving backwards or forwards.

2. A number between 0 and 360.  This dictates the angle of the relative to the screen. 0 being vertically up.

In other words, lets say the first was a value of 2 and the second input was a value of 45, the object would be moving across the screen, forwards, at a fairly low speed and would be traveling up at an angle of 45 degrees (assume 0 degrees is vertically up). If the first input moved to a value of 5 then the speed at which it moved in that direction would be much faster.  If we changed the second input, the object will steer round and head in the corresponding direction.

direction-speed-of-an-object-using-two-inputs

Just search the jitter forum for a thread called "patch for game-like 

navigation through gl space" - it's all in there.

Just search the jitter forum for a thread called "patch for game-like 
navigation through gl space" - it's all in there.

Have looked, still trying to fingure out how to link it up so i can use it prooperly!

Here is some more information on what it is i am trying to achieve:

Take a look at the attached JPG as it shows how it would look.

My biggest problem at th moment, is sorting the maths out so the two values will produce x,y coordinates for the object to move to. 'Input1' (a value between -10 and 10) controls whether our object is moving forwards (+), or backwards (-), and how fast (depending on the value 10 being fastest). The second input, 'Input2' is going to be a value between 0 and 360 which corresponds to the orientation of the object, in degrees, locally to the object (0 being vertically up). So for example, a value of 10 on input1 and value of 45 on input2 will mean that our object (a small dot) is moving diagonally up, towards the right of the screen, at its maximum speed. If the input2 value altered to 270, the direction of the object would change to heading towards the left. Basically these two values act like the two controls on the transmitter of a radio controlled car and we are looking directly down at our RC car which is represented by a dot.

I have the motion tracking of the balloon working. One part of the patch tracks the overall position of the balloon and the other tracks the position of a red dot on the balloon. Input1 uses the 'x' information gathered as raw data and Input2 will use jit.findbounds to calculate the distance from the left-hand side of the balloon to the center of the red dot. We know that the balloon is 6 feet in diameter so we can work out the rotational angle of the balloon and then range this into a sensible value between 0 and 360.

My biggest problem at th moment, is sorting the maths out so the two values will produce x,y coordinates for the object to move to.  'Input1' (a value between -10 and 10) controls whether our object is moving forwards (+), or backwards (-), and how fast (depending on the value 10 being fastest).  The second input, 'Input2' is going to be a value between 0 and 360 which corresponds to the orientation of the object, in degrees, locally to the object (0 being vertically up). So for example, a value of 10 on input1 and value of 45 on input2 will mean that our object (a small dot) is moving diagonally up, towards the right of the screen, at its maximum speed.  If the input2 value altered to 270, the direction of the object would change to heading towards the left.  Basically these two values act like the two controls on the transmitter of a radio controlled car and we are looking directly down at our RC car which is represented by a dot.

I have the motion tracking of the balloon working.  One part of the patch tracks the overall position of the balloon and the other tracks the position of a red dot on the balloon.  Input1 uses the 'x' information gathered as raw data and Input2 will use jit.findbounds to calculate the distance from the left-hand side of the balloon to the center of the red dot.  We know that the balloon is 6 feet in diameter so we can work out the rotational angle of the balloon and then range this into a sensible value between 0 and 360.


Here is a modified version of my glNavigator abstraction. It does exactly what you ask here, tell me if there's anything confusing or incorrect.

Thats brilliant. The next two things I have to do is get it to leave a line where its been and when it creeps off the edge of the screen, come on the other side!

Thanks so much. Here's the raw patch its going onto...

The left hand tracker will be Input1 (forward/backward speed), it will also give me the min bound of the overall balloon. The Right hand side will track the red dot on the balloon. Knowing where the dot is in relation to the edge of the balloon (being that the balloon is 6 feet in diameter) will allow me to translate its rotation. This data, once ranged will be Input2 data! these to sets of data will then control that openGL dots movement.

Basically, there wil be a 6 foot weather balloon and a camera looking at it. I have attached a test movie which crudely simulates the balloon with a dot on it. I can't get into the actual space until Friday so touchh wood I hope this all works out!!! if you have any other ideas as to drawing the line and making the openGL dot wrap I would love to hear them. Hopefully, if I get time i would like to make the line andd dot look a little more interesting.

Thats brilliant.  The next two things I have to do is get it to leave a line where its been and when it creeps off the edge of the screen, come on the other side!

Thanks so much.  Here's the raw patch its going onto...

The left hand tracker will be Input1 (forward/backward speed), it will also give me the min bound of the overall balloon. The Right hand side will track the red dot on the balloon.  Knowing where the dot is in relation to the edge of the balloon (being that the balloon is 6 feet in diameter) will allow me to translate its rotation.  This data, once ranged will be Input2 data!  these to sets of data will then control that openGL dots movement.  

Basically, there wil be a 6 foot weather balloon and a camera looking at it.  I have attached a test movie which crudely simulates the balloon with a dot on it.  I can't get into the actual space until Friday so touchh wood I hope this all works out!!!  if you have any other ideas as to drawing the line and making the openGL dot wrap I would love to hear them.  Hopefully, if I get time i would like to make the line andd dot look a little more interesting.

I haven't read your previous post yet, but I forgot to add objedt-rotation to the previous patch. Here it is, in case you need it.

For leaving a trail, one way to do it is just adjust the alpha of the erase_color attribute in the jit.gl.render object.

As for the having it wrap, you can set your gridshape object to @transform_reset 1. This will make it so the x and y coordinates scale between -1. and 1. in your jitter window. Then you can add the if/then scenarios to have the object wrap (i.e. if $f1 < -1. then 1. else $f1)

For leaving a trail, one way to do it is just adjust the alpha of the erase_color attribute in the jit.gl.render object. 

As for the having it wrap, you can set your gridshape object to @transform_reset 1. This will make it so the x and y coordinates scale between -1. and 1. in your jitter window. Then you can add the if/then scenarios to have the object wrap (i.e. if $f1 < -1. then 1. else $f1)


I got to procrastinating regarding some other things I should have been doing, and, well... here's the result ;) It wraps and there are some trails.

As for the trails, maybe someone else can clear this up for me. I've noticed that when I turn the alpha value of the jit.gl.render's erase_color down far enough, I get trails that never quite go away. I mean, if I want the background to eventually go back to black, and I set the erase_color to 0. 0. 0. 0.1, it may never quite get there. I know this is because I'm telling it to blend with the color of the object. Is there a way though, that I can get it to fade back to pure black over a long period of time, rather than, as in the attached patch, a very dark red (because the gridshape is red). Sorry for the newb question. Can't figure it out...

I got to procrastinating regarding some other things I should have been doing, and, well... here's the result ;) It wraps and there are some trails. 

As for the trails, maybe someone else can clear this up for me. I've noticed that when I turn the alpha value of the jit.gl.render's erase_color down far enough, I get trails that never quite go away. I mean, if I want the background to eventually go back to black, and I set the erase_color to 0. 0. 0. 0.1, it may never quite get there. I know this is because I'm telling it to blend with the color of the object. Is there a way though, that I can get it to fade back to pure black over a long period of time, rather than, as in the attached patch, a very dark red (because the gridshape is red). Sorry for the newb question. Can't figure it out... 

And one more version. This creates trails with jit.gl.sketch. Color changes with speed.

There are some loadbangs and loadmesses inside the p yoursolution subpatch. Easiest way is to save the patch, close it, then reopen it. Tell me if you still can't get it to work after that.

Here are both versions zipped up. I slightly altered the jit.gl.sketch version after posting it.

Well, I have managed to get the erase_color to work and now have trails! I have had a re-think about making the object come on the other side of the screen to which it went off. I think, using that zooming function on the camera would be cool.

When the object reaches within a certain distance of any of the edges, the camera will zoom out a little. This way, the object will never move off the edge of the screen. Just have to figure out how to relay it's x,y coords in order to + an amount onto the camera zoom box if that makes sense.

Well, I have managed to get the erase_color to work and now have trails!  I have had a re-think about making the object come on the other side of the screen to which it went off.  I think, using that zooming function on the camera would be cool.  

When the object reaches within a certain distance of any of the edges, the camera will zoom out a little.  This way, the object will never move off the edge of the screen.  Just have to figure out how to relay it's x,y coords in order to + an amount onto the camera zoom box if that makes sense.

Look inside the p zoom subpatch in this new version. You can fine tune it.

Thats cool, the only problem is that it zooms out only once. When the object hits the edge of the screen again the object then goes off the edge. I need it to pan out again and again.

The other thing is, I don't want the camera to pan back IN ever. What section of that sub patch do I need to alter that?

I have also been trying to get it to draw two objects, one under the other. I white object (very small) and a blue on top(larger). Using the erase_color function...

The idea is that the white dot is drawn under the blue one. The blue one should leave a fading trail, which works successfully and then the white dot under leaves the permanent white trail (the scale of the white dot is 0.05).

b)the fade applies to what ever is in the test render window, i don't know how to separate it so I can have a value of 0.04 on the blue dot's alpha and a value of 0 on the white dots alpha (in the @erase_color attribute) since it has to be added to the jit.render message box.

Thats cool, the only problem is that it zooms out only once.  When the object hits the edge of the screen again the object then goes off the edge.  I need it to pan out again and again.

The other thing is, I don't want the camera to pan back IN ever.  What section of that sub patch do I need to alter that?  

I have also been trying to get it to draw two objects, one under the other.  I white object (very small) and a blue on top(larger).  Using the erase_color function...

The idea is that the white dot is drawn under the blue one.  The blue one should leave a fading trail, which works successfully and then the white dot under leaves the permanent white trail (the scale of the white dot is 0.05).  

I am having trouble getting it to:
a) draw the white dot under the blue 

As I said before, looking inside the p zoom subpatch. I'm modifying the lens_angle to zoom in and out. You should take a look at it and modify it to your liking. It's easy to eliminate zooming back in - adjust the appropriate if objects.

As for rendering one object below another, give them different layer attributes. Give the little white dot a @layer 0 and the balloon @layer 1. The balloon will be on top then.

As for different type of trails simultaneously, you might try applying the jit.gl.sketch that I've been giving you to the little white dot, if you want the trail to be permanent.

As I said before, looking inside the p zoom subpatch. I'm modifying the lens_angle to zoom in and out. You should take a look at it and modify it to your liking. It's easy to eliminate zooming back in - adjust the appropriate if objects. 

As for different type of trails simultaneously, you might try applying the jit.gl.sketch that I've been giving you to the little white dot, if you want the trail to be permanent.


yes, I am playing with the trails patch now. I can't figure out how to stop it from cycling in colour and just make it white. I modified the qlim to 1 so it appears as a solid line and guessed that the gcolor is what i need to adjust to turn it too white but cant get it to change it.

As far as modifying the p zoom expression, because I am going to run at a resolution of 1024x768 I have upped the initial statement to 'if $f1 

yes, I am playing with the trails patch now. I can't figure out how to stop it from cycling in colour and just make it white.  I modified the qlim to 1 so it appears as a solid line and guessed that the gcolor is what i need to adjust to turn it too white but cant get it to change it.

As far as modifying the p zoom expression, because I am going to run at a resolution of 1024x768 I have upped the initial statement to 'if $f1 


Now the trails are only white. I've adjusted the zooming subpatch to zoom out not by using the lens_angle attribute, but by moving out on the z axis. This doesn't distort the sphere. Look inside the 'p ifs' subpatch inside the 'p zoom' subpatch to see how I'm doing it. It only zooms out. Never zooms back in. I'm sure you can take it from here. I've pretty much given you everything you need. Spend some time figuring out what's going on.

Thanks so much for all of your help, you have been more than generous and I cannot express my appreciation enough. I have learn't so much from your patches. Thanks also for your patience. I come from a Flash action scripting background so fundamentally, the principles and concepts of modular programming are there for me and now, thanks to you, my knowledge of the ins and outs of max and jitter have been expanded greatly!

I managed to begin sorting out the if statements last night and things but I have had to share my time with building the installation. It's a mad panic to get it up and i'm pretty exhausted!

Anyhoo, again, many thanks for your help.

Thanks so much for all of your help, you have been more than generous and I cannot express my appreciation enough.  I have learn't so much from your patches.  Thanks also for your patience.  I come from a Flash action scripting background so fundamentally, the principles and concepts of modular programming are there for me and now, thanks to you, my knowledge of the ins and outs of max and jitter have been expanded greatly! 

I managed to begin sorting out the if statements last night and things but I have had to share my time with building the installation.  It's a mad panic to get it up and i'm pretty exhausted!

Direction & Speed of an object using two inputs