RAY_DemoEdgeDetectFilter.C

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/*
 * Copyright (c) 2025
 *      Side Effects Software Inc.  All rights reserved.
 *
 * Redistribution and use of Houdini Development Kit samples in source and
 * binary forms, with or without modification, are permitted provided that the
 * following conditions are met:
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. The name of Side Effects Software may not be used to endorse or
 *    promote products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY SIDE EFFECTS SOFTWARE `AS IS' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN
 * NO EVENT SHALL SIDE EFFECTS SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *----------------------------------------------------------------------------
 * This is a sample pixel filter to do edge detection
 */

#include <UT/UT_DSOVersion.h>

#include "RAY_DemoEdgeDetectFilter.h"
#include <RAY/RAY_SpecialChannel.h>
#include <UT/UT_Args.h>
#include <UT/UT_StackBuffer.h>
#include <SYS/SYS_Floor.h>
#include <SYS/SYS_Math.h>

using namespace HDK_Sample;

RAY_PixelFilter *
allocPixelFilter(const char *name)
{
    // NOTE: We could use name to distinguish between multiple pixel filters,
    //       in the same library, but we only have one.
    return new RAY_DemoEdgeDetectFilter();
}

RAY_DemoEdgeDetectFilter::RAY_DemoEdgeDetectFilter()
    : mySamplesPerPixelX(1) // Initialized just in case; value shouldn't be used
    , mySamplesPerPixelY(1) // Initialized just in case; value shouldn't be used
    , myUseColourGradient(true)
    , myUseZGradient(true)
    , myUseOpID(true)
    , myColourGradientThreshold(0.1f)
    , myZGradientThreshold(0.005f)
    , myColourGradientWidth(3.0f)
    , myZGradientWidth(3.0f)
    , myOpIDWidth(3.0f)
{
}

RAY_DemoEdgeDetectFilter::~RAY_DemoEdgeDetectFilter()
{
}

RAY_PixelFilter *
RAY_DemoEdgeDetectFilter::clone() const
{
    // In this case, all of our members can be default-copy-constructed,
    // so we don't need to write a copy constructor implementation.
    RAY_DemoEdgeDetectFilter *pf = new RAY_DemoEdgeDetectFilter(*this);
    return pf;
}

void
RAY_DemoEdgeDetectFilter::setArgs(int argc, const char *const argv[])
{
    UT_Args args;
    args.initialize(argc, argv);
    args.stripOptions("c:o:s:w:z:");

    // e.g. default values correspond with:
    // -c 0.1 -w 3.0 -z 0.005 -s 3.0 -o 3.0
    // To disable any of the 3 detections, set one of the corresponding
    // parameters to a negative number, like -1

    if (args.found('c'))
    {
        myColourGradientThreshold = args.fargp('c');
        myUseColourGradient = (myColourGradientThreshold >= 0);
        if (myUseColourGradient && args.found('w'))
        {
            myColourGradientWidth = args.fargp('w');
            if (myColourGradientWidth < 0)
                myUseColourGradient = false;
            // NOTE: You could add support for widths < 1.0 by taking the max
            //       of the gradients within a pixel.
            //       The upper limit is just to avoid accidents.
            myColourGradientWidth = SYSclamp(myColourGradientWidth, 1.0f, 1024.0f);
        }
    }
    if (args.found('o'))
    {
        myOpIDWidth = args.fargp('o');
        myUseOpID = (myOpIDWidth >= 0);
        myOpIDWidth = SYSclamp(myOpIDWidth, 1.0f, 1024.0f);
    }
    if (args.found('z'))
    {
        myZGradientThreshold = args.fargp('z');
        myUseZGradient = (myZGradientThreshold >= 0);
        if (myUseZGradient && args.found('s'))
        {
            myZGradientWidth = args.fargp('s');
            if (myZGradientWidth < 0)
                myUseZGradient = false;
            // NOTE: You could add support for widths < 1.0 by taking the max
            //       of the gradients within a pixel.
            //       The upper limit is just to avoid accidents.
            myZGradientWidth = SYSclamp(myZGradientWidth, 1.0f, 1024.0f);
        }
    }
}

void
RAY_DemoEdgeDetectFilter::getFilterWidth(float &x, float &y) const
{
    // NOTE: You could add support for different x and y filter widths,
    //       which might be useful for non-square pixels.
    float filterwidth = SYSmax(myUseColourGradient ? myColourGradientWidth : 1,
                               myUseZGradient ? myZGradientWidth : 1,
                               myUseOpID ? myOpIDWidth : 1);
    x = filterwidth;
    y = filterwidth;
}

void
RAY_DemoEdgeDetectFilter::addNeededSpecialChannels(RAY_Imager &imager)
{
    if (myUseOpID)
        addSpecialChannel(imager, RAY_SPECIAL_OPID);
    if (myUseZGradient)
        addSpecialChannel(imager, RAY_SPECIAL_PZ);
}

namespace {
float RAYcomputeSumX2(int samplesperpixel,float width,int &halfsamplewidth)
{
    float sumx2 = 0;
    if (samplesperpixel & 1)
    {
        // NOTE: This omits the middle sample
        halfsamplewidth = (int)SYSfloor(float(samplesperpixel)*0.5f*width);

        // There's a close form for this sum, but I figured I'd write it out in full,
        // since it's not a bottleneck.
        for (int i = -halfsamplewidth; i <= halfsamplewidth; ++i)
        {
            float x = float(i)/float(samplesperpixel);
            sumx2 += x*x;
        }
    }
    else
    {
        halfsamplewidth = (int)SYSfloor(float(samplesperpixel)*0.5f*width + 0.5f);

        // There's a close form for this sum, but I figured I'd write it out in full,
        // since it's not a bottleneck.
        for (int i = -halfsamplewidth; i < halfsamplewidth; ++i)
        {
            float x = (float(i)+0.5f)/float(samplesperpixel);
            sumx2 += x*x;
        }
    }
    return sumx2;
}
}

void
RAY_DemoEdgeDetectFilter::prepFilter(int samplesperpixelx, int samplesperpixely)
{
    mySamplesPerPixelX = samplesperpixelx;
    mySamplesPerPixelY = samplesperpixely;

    // We can precompute coefficients here
    myColourSumX2 = RAYcomputeSumX2(mySamplesPerPixelX, myColourGradientWidth, myColourSamplesHalfX);
    myColourSumY2 = RAYcomputeSumX2(mySamplesPerPixelY, myColourGradientWidth, myColourSamplesHalfY);
    myZSumX2 = RAYcomputeSumX2(mySamplesPerPixelX, myZGradientWidth, myZSamplesHalfX);
    myZSumY2 = RAYcomputeSumX2(mySamplesPerPixelY, myZGradientWidth, myZSamplesHalfY);
    myOpIDSamplesHalfX = (int)SYSfloor(float(mySamplesPerPixelX)*0.5f*myOpIDWidth + ((mySamplesPerPixelX & 1) ? 0.0f : 0.5f));
    myOpIDSamplesHalfY = (int)SYSfloor(float(mySamplesPerPixelY)*0.5f*myOpIDWidth + ((mySamplesPerPixelY & 1) ? 0.0f : 0.5f));
}

void
RAY_DemoEdgeDetectFilter::filter(
    float *destination,
    int vectorsize,
    const RAY_SampleBuffer &source,
    int channel,
    int sourcewidth,
    int sourceheight,
    int destwidth,
    int destheight,
    int destxoffsetinsource,
    int destyoffsetinsource,
    const RAY_Imager &imager) const
{
    const float *const colourdata = myUseColourGradient
        ? getSampleData(source, channel)
        : NULL;
    const float *const zdata = myUseZGradient
        ? getSampleData(source, getSpecialChannelIdx(imager, RAY_SPECIAL_PZ))
        : NULL;
    const float *const opiddata = myUseOpID
        ? getSampleData(source, getSpecialChannelIdx(imager, RAY_SPECIAL_OPID))
        : NULL;

    UT_ASSERT(myUseColourGradient == (colourdata != NULL));
    UT_ASSERT(myUseZGradient == (zdata != NULL));
    UT_ASSERT(myUseOpID == (opiddata != NULL));

    // The gradient computations can be made much faster by separating x and y,
    // using a temporary buffer, but this is implemented the slow way.
    // In fact, nothing in here is optimized.

    for (int desty = 0; desty < destheight; ++desty)
    {
        for (int destx = 0; destx < destwidth; ++destx)
        {
            bool isedge = false;

            // First, compute the sample bounds of the pixel
            const int sourcefirstx = destxoffsetinsource + destx*mySamplesPerPixelX;
            const int sourcefirsty = destyoffsetinsource + desty*mySamplesPerPixelY;
            const int sourcelastx = sourcefirstx + mySamplesPerPixelX-1;
            const int sourcelasty = sourcefirsty + mySamplesPerPixelY-1;
            // Find the first sample to read for colour and z gradients
            const int sourcefirstcx = sourcefirstx + (mySamplesPerPixelX>>1) - myColourSamplesHalfX;
            const int sourcefirstcy = sourcefirsty + (mySamplesPerPixelY>>1) - myColourSamplesHalfY;
            const int sourcefirstzx = sourcefirstx + (mySamplesPerPixelX>>1) - myZSamplesHalfX;
            const int sourcefirstzy = sourcefirsty + (mySamplesPerPixelY>>1) - myZSamplesHalfY;
            const int sourcefirstox = sourcefirstx + (mySamplesPerPixelX>>1) - myOpIDSamplesHalfX;
            const int sourcefirstoy = sourcefirsty + (mySamplesPerPixelY>>1) - myOpIDSamplesHalfY;
            // Find the last sample to read for colour and z gradients
            const int sourcelastcx = sourcefirstx + ((mySamplesPerPixelX-1)>>1) + myColourSamplesHalfX;
            const int sourcelastcy = sourcefirsty + ((mySamplesPerPixelY-1)>>1) + myColourSamplesHalfY;
            const int sourcelastzx = sourcefirstx + ((mySamplesPerPixelX-1)>>1) + myZSamplesHalfX;
            const int sourcelastzy = sourcefirsty + ((mySamplesPerPixelY-1)>>1) + myZSamplesHalfY;
            const int sourcelastox = sourcefirstx + ((mySamplesPerPixelX-1)>>1) + myOpIDSamplesHalfX;
            const int sourcelastoy = sourcefirsty + ((mySamplesPerPixelY-1)>>1) + myOpIDSamplesHalfY;
            // Find the first and last that will be read
            int sourcefirstrx = sourcefirstx;
            int sourcefirstry = sourcefirsty;
            int sourcelastrx = sourcelastx;
            int sourcelastry = sourcelasty;
            if (myUseColourGradient)
            {
                sourcefirstrx = SYSmin(sourcefirstrx, sourcefirstcx);
                sourcefirstry = SYSmin(sourcefirstry, sourcefirstcy);
                sourcelastrx = SYSmax(sourcelastrx, sourcelastcx);
                sourcelastry = SYSmax(sourcelastry, sourcelastcy);
            }
            if (myUseZGradient)
            {
                sourcefirstrx = SYSmin(sourcefirstrx, sourcefirstzx);
                sourcefirstry = SYSmin(sourcefirstry, sourcefirstzy);
                sourcelastrx = SYSmax(sourcelastrx, sourcelastzx);
                sourcelastry = SYSmax(sourcelastry, sourcelastzy);
            }
            if (myUseOpID)
            {
                sourcefirstrx = SYSmin(sourcefirstrx, sourcefirstox);
                sourcefirstry = SYSmin(sourcefirstry, sourcefirstoy);
                sourcelastrx = SYSmax(sourcelastrx, sourcelastox);
                sourcelastry = SYSmax(sourcelastry, sourcelastoy);
            }

            // Initialize data for use by each of the edge detection methods
            bool opidset = false;
            float opid;

            UT_StackBuffer<float> colourgradientx(vectorsize);
            UT_StackBuffer<float> colourgradienty(vectorsize);
            if (myUseColourGradient)
            {
                for (int i = 0; i < vectorsize; ++i)
                    colourgradientx[i] = 0;
                for (int i = 0; i < vectorsize; ++i)
                    colourgradienty[i] = 0;
            }

            // The z channel only has one component, so its gradient doesn't need arrays.
            float zgradientx = 0;
            float zgradienty = 0;
            float zaverage = 0;
            bool hasfarz = false;
            bool hasnonfarz = false;

            for (int sourcey = sourcefirstry; sourcey <= sourcelastry && !isedge; ++sourcey)
            {
                for (int sourcex = sourcefirstrx; sourcex <= sourcelastrx; ++sourcex)
                {
                    int sourcei = sourcex + sourcewidth*sourcey;

                    if (myUseOpID && sourcex >= sourcefirstox && sourcex <= sourcelastox && sourcey >= sourcefirstoy && sourcey <= sourcelastoy)
                    {
                        // Found edge if not all of the op IDs of the samples match
                        if (!opidset)
                        {
                            opid = opiddata[sourcei];
                            opidset = true;
                        }
                        else if (opid != opiddata[sourcei])
                        {
                            isedge = true;
                            break;
                        }
                    }

                    if (myUseColourGradient || myUseZGradient)
                    {
                        // Find (x,y) of sample relative to *middle* of pixel
                        float x = (float(sourcex) - 0.5f*float(sourcelastx + sourcefirstx))/float(mySamplesPerPixelX);
                        float y = (float(sourcey) - 0.5f*float(sourcelasty + sourcefirsty))/float(mySamplesPerPixelY);

                        if (myUseColourGradient && sourcex >= sourcefirstcx && sourcex <= sourcelastcx && sourcey >= sourcefirstcy && sourcey <= sourcelastcy)
                        {
                            for (int i = 0; i < vectorsize; ++i)
                                colourgradientx[i] += x*colourdata[vectorsize*sourcei + i];
                            for (int i = 0; i < vectorsize; ++i)
                                colourgradienty[i] += y*colourdata[vectorsize*sourcei + i];
                        }
                        if (myUseZGradient && sourcex >= sourcefirstzx && sourcex <= sourcelastzx && sourcey >= sourcefirstzy && sourcey <= sourcelastzy)
                        {
                            // Special case for if nothing was hit, since may sum past FLT_MAX,
                            // and then values won't cancel out to get a gradient of zero.
                            bool farz = (zdata[sourcei] >= 1.0e37);
                            hasfarz |= farz;
                            hasnonfarz |= !farz;
                            if (hasfarz && hasnonfarz)
                            {
                                isedge = true;
                                break;
                            }
                            if (!farz)
                            {
                                zgradientx += x*zdata[sourcei];
                                zgradienty += y*zdata[sourcei];
                                zaverage += zdata[sourcei];
                            }
                        }
                    }
                }
            }

            if (!isedge)
            {
                if (myUseColourGradient)
                {
                    int nx = sourcelastcx-sourcefirstcx+1;
                    int ny = sourcelastcy-sourcefirstcy+1;
                    for (int i = 0; i < vectorsize; ++i)
                        colourgradientx[i] /= (ny*myColourSumX2);
                    float mag2x = 0;
                    for (int i = 0; i < vectorsize; ++i)
                        mag2x += colourgradientx[i]*colourgradientx[i];

                    for (int i = 0; i < vectorsize; ++i)
                        colourgradienty[i] /= (nx*myColourSumY2);
                    float mag2y = 0;
                    for (int i = 0; i < vectorsize; ++i)
                        mag2y += colourgradienty[i]*colourgradienty[i];

                    if ((mag2x + mag2y) >= myColourGradientThreshold*myColourGradientThreshold)
                        isedge = true;
                }
                if (!isedge && myUseZGradient && hasnonfarz)
                {
                    int nx = sourcelastzx-sourcefirstzx+1;
                    int ny = sourcelastzy-sourcefirstzy+1;
                    zaverage /= float(nx)*float(ny);
                    zgradientx /= (ny*myZSumX2*zaverage);
                    zgradienty /= (nx*myZSumY2*zaverage);
                    float mag2x = zgradientx*zgradientx;
                    float mag2y = zgradienty*zgradienty;

                    if ((mag2x + mag2y) >= myZGradientThreshold*myZGradientThreshold)
                        isedge = true;
                }
            }

            float value = isedge ? 1.0f : 0.0f;
            for (int i = 0; i < vectorsize; ++i, ++destination)
                *destination = value;
        }
    }
}