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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