Knobs Bitmap - Question

[tiffy]

I looked around on the Internet but I could not find any answer to my question with regard to Bitmap Knobs...Is there a specific Standard for the Cell Height, Cell Width and Cell Count?

I found the following most common but not necessarily in that order:

Cell Width & Height = 33
Cell Width & Height = 64
Cell Width & Height = 128
Cell Count = 31
Cell Count = 64
Cell Count = 127

But I also found other Widths, Heights and Cell Counts for Bitmap Knobs...so, I wondered if there is a reason for this (especially the Cell Count) or is it just personal preference?

I noticed however that a greater Cell Count would give a more smooth rotation of the knob, but is this the only reason for having a greater Cell Count?

[RJHollins]

Hi Tiffy,

I can't relay any 'standards', but my impression has been, yes, there are some common cell SIZES ... but I think
the user decides how big/small they need a particular knob, button, etc, to a GUI.

As to cell COUNT. I think 127 has a correlation to MIDI values.

I would think that Knobs output Float values, I think the 'limit' would relate to user ability to work within the
screen resolution and mouse accuracy.

Again. Not an expert here, but I've made knobs STEP to coarser steps for when I want, say an eq GAIN to snap to
'reasonable' value resolution ... say 1/4 or 1/2 dB [as an option] to the contiguous control.

If there IS a standard ... I'll be following this thread to learn.

[tulamide]

so, I wondered if there is a reason for this (especially the Cell Count) or is it just personal preference?
I noticed however that a greater Cell Count would give a more smooth rotation of the knob, but is this the only reason for having a greater Cell Count?

The number of single frames (cell count) should be a compromise between high accuracy and smaller footprint. Theoretically, if you have a 300 degree knob, you could have 300 single frames to have one for each single degree. But that's not very practical.
Or for a midi value knob, you could have 128 single frames (0-127). But again, maybe it would be better to have just 64 only switching every two units.

Regarding width and height: Some people create knobs from a center, those can be identified by an odd number of pixels. Others have the bitblt in mind: I'm not sure if it is still the case, but in the past a power of 2 bitmap could be copied faster in memory. This power of 2 rule still applies for 3D-Graphics-Cards and their texture memory.

You shouldn't follow some standard. Instead design the knobs as you need them for your synth. Width and Height don't need to be squared, the sizes don't need to be power of 2s, and the cell count should be as high or low as you wish.

As a rule of thumb, count the pixels of an image, multiply by 4, then multiply that by the cell count. The result is the number of bytes your bitmap strip will occupy in RAM. Example:
16x16 image, 60 cells: 256 * 4 = 1024 * 60 = 61440 Bytes = 60 kB
256x256 img, 128 cells: 65536 * 4 = 262144 * 128 = 33554432 Bytes = 32 MB

[RJHollins]

Thanks T.

This now leads to the NEXT question. What if we went VECTOR knobs instead. What/how is the RAM use calculated ?

[tulamide]

Thanks T.

This now leads to the NEXT question. What if we went VECTOR knobs instead. What/how is the RAM use calculated ?

Very similar, but without the cells. For every module view you use for that vector knob, count width * height * 4

[Spogg]

Some people create knobs from a center, those can be identified by an odd number of pixels.

I didn't know that, interesting point.

For the last few releases I've made my own knobs. You can probably tell
I noticed that many knobs by others had an odd number of cells, so I did the same (101 in my case).
I'm assuming this is so the frame count is symettrical about the centre position, or is there another reason?

Cheers

Spogg

[tulamide]

The number of cells is mostly a result of the creator's thought process. But yes, an odd number of cells would be found often, when having bipolar knobs. One frame for the 0 position, and another 50 per side.

But it would also be possible that it was a knob from 0 - 1: one frame for 0 and another 100 for 0.01 to 1.0

[tiffy]

Thank you, Tula, RJ and Spogg for your input, this was very very informative and a great help to me...appreciate as always.

I will make a note of this valuable info somewhere on my hard disk drive so that it will not be lost.