[chuck-users] WarpTable inconsistency
dtrueman at Princeton.EDU
Mon Mar 16 11:37:44 EDT 2009
otay, will look through this when i have a chance, thanks again kas!
On Mar 15, 2009, at 11:49 PM, Kassen wrote:
> Dear Dan,
> WarpTable seems to have a issue where .lookup() doesn't behave like
> scanning it with another UGen does for values slightly less than 1.
> I think the scanning feature is wrong here, at least scanning
> doesn't behave according to the docs.
> Consider this example that uses WarpTable as a wave-shaper on a sine
> SinOsc s => WarpTable wp => dac;
> //some trickery to offset and scale the input
> Step st => wp;
> .50 => st.next;
> //notice this line; .5 should be fine here yet isn't
> //increasing this to .5 will cause artefacts
> .4997 => s.gain;
> //scale the range back and avoid DC offset
> Step stInv => dac;
> -.1 => stInv.next;
> 2 => wp.gain;
> 200 => s.freq;
> //increase the second value for "drive"
> //this is the bit that's actually useful and interesting here
> //in this case we keep it linear to be able to hear the artefacts
> more clearly.
> wp.coefs([1., 1. ]);
> minute => now;
> Or; to demonstrate the exact same issue in it's most extreme case;
> Step s => WarpTable wp => dac;
> wp.coefs( [1., 1. ] );
> //UGen based index
> 1 => s.next;
> //allow for the value to be updated
> samp => now;
> //both should be 1.000000
> I believe this to be a error.
> Additionally; the various Gen UGens would be a lot easier to use for
> wave shaping if they could have a mode where they would get indexed
> from -1 to 1 and output the same range; this would avoid the need
> for Step ugens and setting gains to compensate like in the top
> example above. Right now they can only be indexed usefully by things
> like Phasor and Envelope and chaining a few can yield interesting
> phase distortion effects using Gen10 but using them in the amplitude
> domain is quite inconvenient, even when they would make a lot of
> sense there. Maybe this would be worthy of consideration, especially
> as some of the pages referenced by the Gen docs do hint at this
> usage as well.
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> chuck-users at lists.cs.princeton.edu
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