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There is an archive of past mail which can be found at the
technical
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password will be presented.
At the current time, the mailing list has very very low
bandwidth.
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Do I need the C++ development option from SGI? Or can I use another
C++ compiler (like GNU)?
You must use the SGI C++ development option. We are currently using
the 4.0 version of the IDO.
The Photon C++ compiler supposedly works as a replacement for the
SGI compilers, but we currently believe that there are problems
creating .so files with this compiler.
For WindowsNT development, the Microsoft C++ compiler is
required.
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What does the findPointAttrib() method do?
Our geometry library allows arbirtrary attributes on
points/vertices/primities and the detail itself. Each attribute
may be an array of floats, integers, a vector (which gets
transformed) or an indexed array of strings.
Looking in GEO_Detail.h, you'll see a bunch of methods to deal
with attributes:
Add an attribute to a data type
Find an attribute if it exists
Destroy an attribute
The add/find methods return an index for the attribute. If the
index is >= 0, then the attribute exists, and the index can be
used to get the attribute data... For example:
int color;
float ones[3];
ones[0] = ones[1] = ones[2] = 1;
color = gdp->addPointAttrib("Color", sizeof(float)*3,
GB_ATTRIB_FLOAT, (void *)ones);
The above code adds an attribute called "Color" which is
considered to be 3 floating point numbers. The initial value for
the attribute data is set to {1,1,1} (based on the default passed
in). This means, that whenever a point gets added, it will have
its color initialized to 1,1,1. Now, what we'll want to do is
assign values to the attribute data for the data elements...
int i;
GEO_Point *ppt;
float *cptr; // Pointer to the color data
for (i = 0; i < gdp->points().entries(); i++)
{
ppt = gdp->points()(i);
// Use the index that we were returned in the example
// above
cptr = (float *)ppt->getAttribData(color);
cptr[0] = ....;
cptr[1] = ....;
cptr[2] = ....;
}
If we want to destroy the attribute:
gdp->destroyPointAttrib("Color", sizeof(float)*3,
GB_ATTRIB_FLOAT);
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How are ranges set for slider gadgets? I've been noodling through
PRM_Range, and PRM_Template, but an example would be so much clearer for
a neophyte.
If you look at the constructor for PRM_Template, you'll see:
PRM_Template(PRM_Type thetype,
PRM_Name *thenameptr,
PRM_Default *thedefaults,
PRM_ChoiceList *thechoices,
PRM_Range *therange,
PRM_Callback thecallbackfunction,
void *thespareptr)
So, simply define a range, and pass it in when you define your
template for the parameter. Here's an example:
static PRM_Range range(PRM_RANGE_RESTRICTED, 0,
PRM_RANGE_UI, 100)
This defines a range which is totally restricted to a minimum
value of 0. When you evaluate the parameter, it will never return
a negative number. The upper limit of the range is set to 100.
This is a "UI" range. In other words, the user can override the
slider and enter a number bigger than 100.
To reference this range:
PRM_Template(PRM_FLT_J, 1, &myName, 0, 0, &range);
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Why don't my gadgets show up? I've extended myTemplateList[] and
names[], but they don't appear.
When Houdini creates your SOP the very first time. It creates a
UI file which defines the layout of the parameters. It's possible
for you to customize this layout if you like by editing the UI
file.
However, Houdini isn't smart enough to time-stamp the UI files,
therefore, if you change your parameter list, you have to remove
the UI file so that Houdini will create a new one (similar to
dialog scripts).
These UI files are created somewhere writable in your Houdini
search path. The files are created as high up as possible in the
path, so look for the files in:
or if all else fails, these UI files will be created in
/usr/tmp/Dialogs.
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How do I determine if an OBJ_Node * refers to a geometry object or
a null object?
In fact, a null object is identical to a geometry object (they use
the same templates for construction). However, the null object
has a different parameter set displayed in the UI file. This was
done by customizing the UI file.
The way to differentiate between the two similar OPs is to get at
the OP_Operator entry. There is a method in
OP_Parameters::getOperator() which returns a pointer to
the operator. From this, you can get at the name of the operator.
OP_Operator *entry;
entry = obj->getOperator();
if (entry->getName() == "null")
cerr << obj->getName() << " is a null object\n";
else cerr << obj->getName() << " is a " << entry->getName()
<< " object\n";
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How do I do variable expansion on a string? And how do I
determine if it's changing over time?
There's some misleading code in PRM_Parm.h. The
isTimeDependent() method actually only works for animated
parameters (not strings). However, there's a method in the
CH_Manager class which will expand strings for you. It returns an
inteteger 1 if the string is time dependent. So, instead of
evaluating the parameter as an expanded string, evaluate it
without expansion. Then simply call the channel manager to do the
expansion for you and use the return code to determine whether the
string is time dependent.
UT_String raw_string, expanded;
OBJ_Node *node;
obj->evalString(raw_string, "ri_shader", 0, now, 0);
if (OPgetDirector()->getChannelManager()->expandString(
raw_string, expanded_string, now, obj->getChannels()))
{
cerr << "ri_shader changes over time for "
<< obj->getName() << endl;
}
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I've just added some custom expressions. How do I add help in the
textport for them?
If you look in $HFS/houdini/help, you should see two files,
exprhelp, and command.help. These are simple ASCII
files which contain help (in different formats) for expressions
and commands. Instead of modifying the help in $HFS, you can
create a smaller file which contains only the help for your
commands. This file can go anywhere within the Houdini search
path (i.e. /usr/local/houdini/help, $HOME/houdini/help,
$HIP/houdini/help, etc.). The help files are all merged together
when displaying help.
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How can I force my OP to be frame dependent (i.e. whenever the
frame changes, I want my OP to cook, even if there are no
channels)?
In the cook method, simply add the following line:
OP_Node::flags().timeDep = 1;
This has to be set every time the OP cooks since it's possible for
the dependency to change from time to time.
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My SOP doesn't load into Houdini.
This is most likely due to a DSO error. An external library may
not be referenced properly, there might be missing symbols in the
DSO etc. On SGI's try setting the environment variable
% setenv HOUDINI_DSO_ERROR
This will cause DSO errors to be printed to the window shell when
the DSO is accessed. They should appear if you run hscript or
houdini.
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