Item mandelbrot
Item_mandelbrot is a basic example plugin. This wiki page is intended as a walkthrough of the code in order to help you better understand the SDK.
This plugin adds the mandelbrot pattern to modo. A mandelbrot is a shading pattern that you overlay onto whatever you wish.
You can access the pattern by going to the model tab->Shading->Add Layer->mandelbrot.
A unit sphere before the mandelbrot patter is applied
The two sides of the above unit sphere after the mandelbrot pattern is applied
Contents
Code Walkthrough
Class Declarations
We want to create a filter with which to apply our mandelbrot pattern. First, we inherit from CLxImpl_StackFilter to be able to compare, query, and convert our filter. We then inherit from CLxImpl_ImageFilter to be able to actually build an image filter, as the mandelbrot pattern is ultimately an image. Finally, we inherit from CLxImpl_ImageFilterMetrics so we can can keep track of the values in the filter.
class CMandelbrotFilter :
public CLxImpl_StackFilter,
public CLxImpl_ImageFilter,
public CLxImpl_ImageFilterMetrics
{
public:
CMandelbrotPackage *src_pkg;
CLxUser_GradientFilter g_filt[4];
unsigned i_w, i_h, i_max;
double x_0, x_s, y_0, y_s;
float s_col[4];
CLxUser_ImageWrite w_img;
float *f_buf;
double max_log;
bool use_image, gen_buffer;
const char * filt_Type (void) LXx_OVERRIDE;
unsigned filt_Compare (ILxUnknownID other) LXx_OVERRIDE;
LxResult filt_Convert (ILxUnknownID other) LXx_OVERRIDE;
unsigned imf_Type (void) LXx_OVERRIDE;
LxResult imf_Generate (int width, int height, ILxUnknownID monitor, void **ppvObj) LXx_OVERRIDE;
LxResult imfmet_Generate (LXtImageMetrics *metrics) LXx_OVERRIDE;
private:
LxResult GenerateFullFilter (void);
LxResult GenerateSmallFilter (const int w, const int h, CLxUser_ImageWrite &wimg);
void GenerateFBuffer (const int w, const int h, float *fbuf);
void ConvertFBufferToImage (const float *fbuf, const int w, const int h, CLxUser_ImageWrite &wimg);
};
We want to be able to create threads and then share our work among them, so we inherit from CLxImpl_SharedWork.
class CMandlebrotWork :
public CLxImpl_SharedWork
{
public:
CMandelbrotFilter *src_filt;
float *fbuf;
int i_y, n_y, w, h;
LxResult share_Evaluate ();
LxResult share_Spawn (void **ppvObj);
LxResult share_Share (ILxUnknownID other, unsigned int split);
float Pixel (double x, double y);
};
We want to implement our package by creating an instance of it, so we inherit from the CLxImpl_PackageInstance class. We also need some of the methods that CLxImpl_VideoClipItem, as the superclass of all image related clips, includes so we inherit from it.
class CMandelbrotInstance :
public CLxImpl_PackageInstance,
public CLxImpl_VideoClipItem
{
public:
CMandelbrotPackage *src_pkg;
CLxUser_Item m_item;
LxResult pins_Initialize (ILxUnknownID item, ILxUnknownID super) LXx_OVERRIDE;
void pins_Cleanup (void) LXx_OVERRIDE;
LxResult vclip_PrepFilter (ILxUnknownID eval, void **cache) LXx_OVERRIDE;
LxResult vclip_AllocFilter (ILxUnknownID attr, void *cache, void **ppvObj) LXx_OVERRIDE;
void vclip_Cleanup (void *cache) LXx_OVERRIDE;
typedef struct st_GenData {
unsigned w, h, cx, cy;
unsigned rad, grd, col;
unsigned itr;
} GenData;
};
We want to construct a package for the mandelbrot filter, so we inherit from CLxImpl_Package.
class CMandelbrotPackage :
public CLxImpl_Package
{
public:
CLxUser_ImageService img_svc;
static LXtTagInfoDesc descInfo[];
LxResult pkg_SetupChannels (ILxUnknownID addChan) LXx_OVERRIDE;
LxResult pkg_TestInterface (const LXtGUID *guid) LXx_OVERRIDE;
LxResult pkg_Attach (void **ppvObj) LXx_OVERRIDE;
};
This class creates a factory for all the exported objects that are not servers. Only CMandelBrotPackage is exported as a server in this fle. Since the polymorph object has to exist for the lifetime of any instance, the are explicitly allocated as part of the global module and freed at shutdown.
class CFactories {
public:
CLxPolymorph<CMandelbrotInstance> inst;
CLxPolymorph<CMandelbrotFilter> filt;
CLxPolymorph<CMandlebrotWork> work;
CFactories ()
{
inst.AddInterface (new CLxIfc_PackageInstance <CMandelbrotInstance>);
inst.AddInterface (new CLxIfc_VideoClipItem <CMandelbrotInstance>);
filt.AddInterface (new CLxIfc_StackFilter <CMandelbrotFilter>);
filt.AddInterface (new CLxIfc_ImageFilter <CMandelbrotFilter>);
filt.AddInterface (new CLxIfc_ImageFilterMetrics<CMandelbrotFilter>);
work.AddInterface (new CLxIfc_SharedWork <CMandlebrotWork>);
}
} *pF;
Server Tags
The tags here indicate that our Mandelbrot item type is a subtype of video clip meaning an image that may change over time.
LXtTagInfoDesc CMandelbrotPackage::descInfo[] = {
{ LXsPKG_SUPERTYPE, LXsITYPE_VIDEOCLIP },
{ 0 }
};
Initialize
This function exports a server with the package and staticdesc interfaces that is dependent on the CMandelbrotPackage. It also creates the factories using the function references in 138-164.
void
initialize ()
{
CLxGenericPolymorph *srv;
srv = new CLxPolymorph<CMandelbrotPackage>;
srv->AddInterface (new CLxIfc_Package <CMandelbrotPackage>);
srv->AddInterface (new CLxIfc_StaticDesc<CMandelbrotPackage>);
thisModule.AddServer ("mandelbrot", srv);
pF = new CFactories;
}
Helper Function
This function destroys the factories so they can persist while their objects are in use.
void
cleanup ()
{
delete pF;
}
Implementations
Here the channels for the package are created and their default values set using the AddChannel interface and the NewChannel utility
#define Cs_ITERATIONS "iterations"
#define Cs_SIZE "size"
#define Cs_CENTER "center"
#define Cs_RADIUS "radius"
#define Cs_COLOR "color"
#define Cs_SETCOL "setColor"
LxResult
CMandelbrotPackage::pkg_SetupChannels (
ILxUnknownID addChan)
{
CLxUser_AddChannel ac (addChan);
double vec[4];
ac.NewChannel (Cs_ITERATIONS, LXsTYPE_INTEGER);
ac.SetDefault (0.0, 255);
ac.NewChannel (Cs_SIZE, LXsTYPE_PIXEL);
ac.SetVector (LXsCHANVEC_XY);
ac.SetDefault (0.0, 512);
ac.NewChannel (Cs_CENTER, LXsTYPE_UVCOORD);
ac.SetVector (LXsCHANVEC_XY);
vec[0] = -0.5;
vec[1] = 0.0;
ac.SetDefaultVec (vec);
ac.NewChannel (Cs_RADIUS, LXsTYPE_UVCOORD);
ac.SetDefault (1.0, 0);
ac.NewChannel (Cs_COLOR, LXsTYPE_COLOR1);
ac.SetVector (LXsCHANVEC_RGBA);
ac.SetGradient (LXsTYPE_FLOAT);
ac.SetDefault (1.0, 0);
ac.NewChannel (Cs_SETCOL, LXsTYPE_COLOR1);
ac.SetVector (LXsCHANVEC_RGBA);
vec[0] = 0.0;
vec[1] = 0.0;
vec[2] = 0.0;
vec[3] = 1.0;
ac.SetDefaultVec (vec);
return LXe_OK;
}
This section uses TestInterface so that nexus knows what interfaces instances of this package support. This is necessary as to prevent query loops.
LxResult
CMandelbrotPackage::pkg_TestInterface (
const LXtGUID *guid)
{
return (pF->inst.TestInterface (guid) ? LXe_TRUE : LXe_FALSE);
}
Here, Attach is called to create a new instance of this item. The returned object implements a specific item of this type in the scene using the Alloc method.
LxResult
CMandelbrotPackage::pkg_Attach (
void **ppvObj)
{
CMandelbrotInstance *brot = pF->inst.Alloc (ppvObj);
brot->src_pkg = this;
return LXe_OK;
}
The instance is the implementation of the item, and this set of code allocates one for each item in the scene. The instant can respond to a set of events.
LxResult
CMandelbrotInstance::pins_Initialize (
ILxUnknownID item,
ILxUnknownID super)
{
m_item.set (item);
return LXe_OK;
}
The VideoClipItem interface allows this item to function as a generic video clip. PrepFilter allows the item to select channels needed for filter allocation, and record the indices for those in a cache.
LxResult
CMandelbrotInstance::vclip_PrepFilter (
ILxUnknownID evalObj,
void **cache)
{
CLxUser_Evaluation eval (evalObj);
GenData *gd;
gd = new GenData;
if (!gd)
return LXe_FAILED;
gd->itr = eval.AddChan (m_item, Cs_ITERATIONS );
gd->w = eval.AddChan (m_item, Cs_SIZE ".X");
gd->h = eval.AddChan (m_item, Cs_SIZE ".Y");
gd->cx = eval.AddChan (m_item, Cs_CENTER ".X");
gd->cy = eval.AddChan (m_item, Cs_CENTER ".Y");
gd->rad = eval.AddChan (m_item, Cs_RADIUS );
gd->col = eval.AddChan (m_item, Cs_SETCOL ".R");
eval.AddChan (m_item, Cs_SETCOL ".G");
eval.AddChan (m_item, Cs_SETCOL ".B");
eval.AddChan (m_item, Cs_SETCOL ".A");
gd->grd = eval.AddChan (m_item, Cs_COLOR ".R");
eval.AddChan (m_item, Cs_COLOR ".G");
eval.AddChan (m_item, Cs_COLOR ".B");
eval.AddChan (m_item, Cs_COLOR ".A");
cache[0] = gd;
return LXe_OK;
}
AllocFilter creates the image filter for a given frame.
LxResult
CMandelbrotInstance::vclip_AllocFilter (
ILxUnknownID attrObj,
void *cache,
void **ppvObj)
{
CLxUser_Attributes attr (attrObj);
GenData *gd = (GenData *) cache;
CMandelbrotFilter *filt;
float cx, cy, rad;
filt = pF->filt.Alloc (ppvObj);
filt->src_pkg = src_pkg;
filt->i_max = attr.Int (gd->itr);
filt->i_w = attr.Int (gd->w);
filt->i_h = attr.Int (gd->h);
filt->f_buf = 0;
cx = attr.Float (gd->cx);
cy = attr.Float (gd->cy);
rad = attr.Float (gd->rad);
filt->x_0 = cx - rad;
filt->y_0 = cy - rad;
filt->x_s = rad * 2.0;
filt->y_s = rad * 2.0;
for (int i = 0; i < 4; i++) {
filt->s_col[i] = attr.Float (gd->col + i);
attr.ObjectRO (gd->grd + i, filt->g_filt[i]);
}
filt->use_image = false;
filt->gen_buffer = true;
return LXe_OK;
}
This section cleans up some data.
void
CMandelbrotInstance::vclip_Cleanup (
void *cache)
{
GenData *gd = (GenData *) cache;
delete gd;
}
This section places the image onto the image stack where it generates target image on the fly
const char *
CMandelbrotFilter::filt_Type (void)
{
return "benoit_mandelbrot";
}
unsigned
CMandelbrotFilter::imf_Type (void)
{
return LXi_IMAGE_GENERATOR;
}
This uses Compare to compare a filter which has been evaluated to a new one being computed. If the size has changed we require the image to be remade from scratch. For other changes the past result is compatible with the current result so some previous work can be reused.
unsigned
CMandelbrotFilter::filt_Compare (
ILxUnknownID other)
{
CMandelbrotFilter *filt = pF->filt.Cast (other);
CLxUser_Value val;
if (filt->i_w != i_w || filt->i_h != i_h)
return LXiSTACK_DIFFERENT;
if (filt->x_0 != x_0 || filt->x_s != x_s || filt->y_0 != y_0 || filt->y_s != y_s)
return LXiSTACK_COMPATIBLE;
if (filt->i_max != i_max)
return LXiSTACK_COMPATIBLE;
for (int i = 0; i < 4; i++) {
if (filt->s_col[i] != s_col[i])
return LXiSTACK_COMPATIBLE;
val.set (g_filt[i]);
if (val.Compare (filt->g_filt[i]))
return LXiSTACK_COMPATIBLE;
}
return LXiSTACK_IDENTICAL;
}
This section will be called to convert a past evaluation to a compatible filter. We always use the existing image, and if only the color parameters have changed we can reuse the previous gradient input map.
LxResult
CMandelbrotFilter::filt_Convert (
ILxUnknownID other)
{
CMandelbrotFilter *filt = pF->filt.Cast (other);
use_image = true;
gen_buffer = (filt->x_0 != x_0 || filt->x_s != x_s ||
filt->y_0 != y_0 || filt->y_s != y_s ||
filt->i_max != i_max);
x_0 = filt->x_0;
x_s = filt->x_s;
y_0 = filt->y_0;
y_s = filt->y_s;
i_max = filt->i_max;
for (int i = 0; i < 4; i++) {
s_col[i] = filt->s_col[i];
g_filt[i].set (filt->g_filt[i]);
}
return LXe_OK;
}
Here, generators allocate an image and fill it in. This filter maintains a reference to the image so it can be reused as needed. Filters that generate and forget would instead simply return the image.
LxResult
CMandelbrotFilter::imf_Generate (
int width,
int height,
ILxUnknownID monitor,
void **ppvObj)
{
LxResult res;
if (width == i_w && height == i_h) {
res = GenerateFullFilter ();
if (LXx_OK (res))
res = w_img.get (ppvObj);
}
else if (w_img.test () && use_image && !gen_buffer && f_buf) {
ConvertFBufferToImage (f_buf, i_w, i_h, w_img);
res = w_img.get (ppvObj);
}
else {
CLxUser_Image img;
CLxUser_ImageWrite wimg;
src_pkg->img_svc.New (img, width, height, LXiIMP_RGBA32);
wimg.set (img);
res = GenerateSmallFilter (width, height, wimg);
wimg.get (ppvObj);
}
return res;
}
Generate full filter(the main function in this section) will create the image filter at its full size, using the width and height from the channels on the Mandelbrot item.
LxResult
CMandelbrotFilter::GenerateFullFilter (void)
{
/*
* Allocate an image if we need one. We'll hold on to the writable one.
*/
if (!w_img.test () || !use_image) {
CLxUser_Image img;
src_pkg->img_svc.New (img, i_w, i_h, LXiIMP_RGBA32);
w_img.set (img);
if (f_buf) {
delete[] f_buf;
f_buf = 0;
}
}
/*
* Allocate the gradient input buffer.
*/
if (!f_buf) {
f_buf = new float[i_w * i_h];
if (!f_buf)
return LXe_OUTOFMEMORY;
}
/*
* Unless we have a valid buffer we must compute it
*/
if (gen_buffer)
GenerateFBuffer (i_w, i_h, f_buf);
/*
* Finally, convert the buffer to the image
*/
ConvertFBufferToImage (f_buf, i_w, i_h, w_img);
return LXe_OK;
}
Generate small filter does the same as above, except it works on a smaller resolution, using a temporary float buffer. GenerateFBuffer() converts the buffer to the image
LxResult
CMandelbrotFilter::GenerateSmallFilter (
const int w,
const int h,
CLxUser_ImageWrite &wimg)
{
float *fbuf = NULL;
fbuf = new float[w * h];
if (!fbuf)
return LXe_OUTOFMEMORY;
/*
* We compute the buffer
*/
GenerateFBuffer (w, h, fbuf);
/*
* Finally, convert the buffer to the image
*/
ConvertFBufferToImage (fbuf, w, h, wimg);
return LXe_OK;
}
We generate the buffer in the threads. We allocate a work object using Alloc(F), initialize it to the image and process it.
void
CMandelbrotFilter::GenerateFBuffer (
const int w,
const int h,
float *fbuf)
{
CLxUser_ThreadService mt;
CMandlebrotWork *work;
LXtObjectID workObj;
work = pF->work.Alloc (&workObj);
work->src_filt = this;
work->i_y = 0;
work->n_y = h;
work->w = w;
work->h = h;
work->fbuf = fbuf;
max_log = log ((double) i_max);
mt.ProcessShared ((ILxUnknownID) workObj);
lx::ObjRelease (workObj);
}
This section converts the raw buffered values to colors. This could be done in the workers too, since setting pixels should be thread-safe.
void
CMandelbrotFilter::ConvertFBufferToImage (
const float *fbuf,
const int w,
const int h,
CLxUser_ImageWrite &wimg)
{
LXtImageFloat pixel[4];
unsigned x, y, k;
double d;
for (y = 0; y < h; y++) {
for (x = 0; x < w; x++) {
d = fbuf[y * h + x];
if (d < 0.0)
for (k = 0; k < 4; k++)
pixel[k] = s_col[k];
else
for (k = 0; k < 4; k++)
pixel[k] = g_filt[k].Evaluate (d);
wimg.SetPixel (x, y, LXiIMP_RGBAFP, pixel);
}
}
}
Adds a metrics interface for getting size and type info.
LxResult
CMandelbrotFilter::imfmet_Generate (
LXtImageMetrics *metrics)
{
metrics->maxRes[0] = i_w;
metrics->maxRes[1] = i_h;
metrics->pixelType = LXiIMP_RGBA32;
metrics->aspect = 1.0;
metrics->filename[0] = 0;
metrics->format[0] = 0;
return LXe_OK;
}
The class created here(CMandelbrotWork) is a way to spread the work among threads. Each work object holds a current line and number of lines remaining initialized to zero. The master work object will be initialized to the total lines in the image, and the threading system will allocate enough new work objects to keep the system's core busy.
LxResult
CMandlebrotWork::share_Spawn (
void **ppvObj)
{
CMandlebrotWork *work;
work = pF->work.Alloc (ppvObj);
*work = *this;
work->i_y = 0;
work->n_y = 0;
return LXe_OK;
}
Work objects that have work will be asked to share with those that don't. In this case we transfer one line from this work object to the other. This is currently the only valid split mode, although it could transfer more lines to reduce contention.
LxResult
CMandlebrotWork::share_Share (
ILxUnknownID other,
unsigned int split)
{
CMandlebrotWork *take = pF->work.Cast (other);
if (n_y <= 1)
return LXe_FALSE;
take->i_y = i_y;
take->n_y = 1;
i_y ++;
n_y --;
return LXe_TRUE;
}
Evaluate(the main function here) processes one piece of work, in this case a line of the image. The floating point buffer is filled with values from -1 to 1.
LxResult
CMandlebrotWork::share_Evaluate ()
{
double u, v;
if (n_y <= 0)
return LXe_FALSE;
v = i_y / (double) h;
for (int x = 0; x < w; x++) {
u = x / (double) w;
fbuf[i_y * h + x] = Pixel (u, v);
}
i_y ++;
n_y --;
return LXe_TRUE;
}
Here, we compute a single pixel. This is the standard Mandelbrot loop, except that the final iteration count is scaled 0 to 1 in a log scale. Points in the set are assigned -1.
float
CMandlebrotWork::Pixel (
double x,
double y)
{
std::complex<double> z (0.0, 0.0);
std::complex<double> c (src_filt->x_0 + src_filt->x_s * x,
src_filt->y_0 + src_filt->y_s * y);
unsigned i;
for (i = 1; i <= src_filt->i_max; i++) {
z = z * z + c;
if (abs (z) > 2.0)
return log ((double) i) / src_filt->max_log;
}
return -1.0;
}
