Hey Steve,
thanks heaps for your writeup! To give you an idea of my background,
I've been comping and python scripting Nuke for a few years, but only
recently attended a class for C++ and am diving into the NDK. So I'm
still fairly new to the NDK and C++ in general.
When you explained that 'channels' may only contain channels being
requested of the node by nodes downstream, that was a pretty
revolutionary perspective change for me!
Though adding the if(ch_pw) doesn't prevent the node from crashing, I
think we're getting somewhere.
A couple questions;
-- When running foreach(z, channels); I presume based on your
explanation that "z" does not represent an integer? for some reason I
was thinking it represented an integer (which is why I used it to
index pw[z])-
because I assumed "z" would be an integer range from 0-3.
If I understand you right, "z" could actually be a "Depth.Z" channel
and not an integer like 1. So unless the point world knob contains
Depth.Z (which it wouldn't) this would always be NULL.
-- How are the ChannelMask and ChannelSet classes different from each
other? (and even with the class method PointSample:in_channels()
ChannelSet& is defined as "mask" which I find confusing).
I'm re-reading the documentation again- although I'm hacking together
code from alot of different source examples, I still don't really get
how to bring in a specified layer and access those channels..
Cheers,
Jordan
On Thu, May 17, 2012 at 3:43 AM, Steven Booth <sbo...@legend3d.com> wrote:
> Jordan,
>
>
>
> I think I see what might be the problem here. You define ch_'pw' like this
>
>
>
> Channel ch_pw = pw[z];
>
>
>
> And then use it like this:
>
>
>
> const float* pw_ptr = in[ch_pw] + x;
>
>
>
> Here’s the secret: You have absolutely no guarantee what ‘channels’
> contains. ‘channels’ are the channels *being requested of you by the
> downstream node*. If you hook a shuffle up to your node (Op), and shuffle
> Depth.Z into R, then ‘Depth.Z’ is going to be placed into the ‘channels’
> ChannelSet passed to your _engine call.
>
>
>
> If, then, your ‘point world’ ChannelSet isn’t requested, or isn’t fully
> requested, then pw[z] is going to eventually return NULL. That makes
> ‘ch_pw’ NULL, and when you do the ‘in[ch_pw]’, *that* is going to be null,
> which makes pw_ptr NULL, which kind of makes:
>
>
>
> float a = *pw_ptr++;
>
>
>
> somewhat (well… more like ‘really’) invalid.
>
>
>
> What you always need to do is make sure the channel you’re processing is
> actually being asked for… that your channel references are non-null so:
>
>
>
> Channel ch_pw = pw[z];
>
> If (ch_pw) {
>
> … code that uses ‘ch_pw’
>
> }
>
>
>
> So, the inner code is only used if ‘ch_pw’ is not null.
>
>
>
> Hope that helps
>
>
>
> Steve
>
>
>
>
>
>
>
>
>
> -----Original Message-----
> From: nuke-dev-boun...@support.thefoundry.co.uk
> [mailto:nuke-dev-boun...@support.thefoundry.co.uk] On Behalf Of Jordan Olson
> Sent: Tuesday, May 15, 2012 5:56 PM
> To: Nuke plug-in development discussion
> Subject: [Nuke-dev] Inexperienced NDK simple question on pixelIop channels
>
>
>
> hey fellow Nuke developers!
>
> I'm writing a pixelIop node at the moment, and having difficulty figuring
> out some code.
>
>
>
> I have an extra knob for "Point World" channelset, and to test it, I'm
> trying to copy the pixel values from this set into the standard channels
> specified by the user. (default RGBA).
>
> However it's crashing, and I think I need to implement something like the
> following example taken from the IDistort Iop code:
>
>
>
>
>
> // missing channels will crash, use black instead:
>
> Channel uu = uv[0];
>
> Channel vv = uv[1];
>
> if (!intersect(tile.channels(), uu))
>
> uu = Chan_Black;
>
> if (!intersect(tile.channels(), vv))
>
> vv = Chan_Black;
>
>
>
>
>
> However this ^ is from an Iop node, and I'm having a crash on a PixelIop. Is
> there a similar function I could implement on my pixel operator?
>
> Here is my code below, slightly simplified for readability.
>
>
>
>
>
>
>
> ............
>
>
>
> void PointSample::_validate(bool for_real){
>
> copy_info();
>
> set_out_channels(Mask_All);
>
> }
>
>
>
> void PointSample::in_channels(int input, ChannelSet& mask) const {
>
> mask += (pw[0]);
>
> mask += (pw[1]);
>
> mask += (pw[2]);
>
> }
>
>
>
> void PointSample::pixel_engine(const Row& in, int y, int x, int r,
> ChannelMask channels, Row& out) {
>
> foreach (z, channels)
>
> {
>
> const float* inptr = in[z]+x;
>
> const float* END = inptr+(r-x);
>
>
>
> Channel ch_pw = pw[z];
>
> // This doesn't compile because the Pixel Iop has no tile
> functionality
>
> /*
>
> if (!intersect(tile.channels(), ch_pw))
>
> ch_pw = Chan_Black;
>
> */
>
>
>
> const float* pw_ptr = in[ch_pw] + x;
>
> float* outptr = out.writable(z)+x;
>
>
>
> while (pw_ptr < END)
>
> {
>
> float a =
> *pw_ptr++;
>
> *outptr++ =
> a;
>
> }
>
>
>
> }
>
> }
>
>
>
> ............
>
>
>
>
>
> cheers if you could point out why this is crashing!
>
> Jordan
>
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