MyGraphics3D.prejava

// 3D Graphics pipeline
// built on top of MyGraphics.
#include "macros.h"

import com.donhatchsw.util.MyMath;
import com.donhatchsw.util.VecMath;

public class MyGraphics3D extends MyGraphics
{
    //
    // How should this work?
    //         M     V          P        /w                 viewport
    //    4d    4d    4d         4d         3d                      2d
    //    homo  homo  homo       homo       (non-normalized)        window/pixel
    //    model world eye/cam    clip       device                  space
    //    space space space      space      space
    //                (lighting) (clipping) [-x0,x1]x[-y0,y1]       [0,width]x[height,0]
    //
    // The MyGraphics3D class contains the MVP matrix
    // (all composed together).
    // The viewport transformation is handled by the base class (MyGraphics).
    //
    // The caller creates the MyGraphics3D from:
    //     java.awt.Graphics g
    //     java.awt.Dimension gsize
    //     x0,x1,y0,y1 bounds of (non-normalized) clip space
    //     MVP matrix
    // 

    public MyGraphics3D(java.awt.Graphics g,
                        java.awt.Dimension gsize,
                        double x0, double x1, double y0, double y1,
                        double MVP[][]) // assumed immutable
    {
        super(g, gsize, x0,x1,y0,y1);
        this.xformMat = MVP;
        this.clipBounds = new double[][] {{x0,x1},{y0,y1}};

        if (this.debugClip)
        {
            // debug by setting clip to half what it was
            VecMath.mxs(clipBounds, clipBounds, .5);
        }
    }

    public void drawLine(double x0, double y0, double z0, double w0,
                         double x1, double y1, double z1, double w1,
                         boolean antiAlias)
    {
        double q0[] = scratch0;
        double q1[] = scratch1;
        double dir[] = scratch2;
        double t0t1[] = scratch3;
        xformNoDivide(x0,y0,z0,w0, q0);
        xformNoDivide(x1,y1,z1,w1, q1);
        VecMath.vmv(dir, q1,q0);
        clipToBoxHomo(q0, dir, 0., 1.,
                          this.clipBounds,
                          t0t1);
        double t0 = t0t1[0];
        double t1 = t0t1[1];
        if (t0 <= t1) // if not completely clipped away
        {
            VecMath.vpsxv(q1, q0, t1, dir); // needs original q0, so do this first
            VecMath.vpsxv(q0, q0, t0, dir); // clobbers q0, so do this second
            w0 = q0[3];
            w1 = q1[3];
            if (w0 != 0. && w1 != 0.) // can be zero if line passes through eye, ouch!
                super.drawLineNonClipped(q0[0]/w0, q0[1]/w0,
                                         q1[0]/w1, q1[1]/w1,
                                         antiAlias);
        }
    } // drawLine

    public void drawLine(double x0, double y0, double z0,
                         double x1, double y1, double z1,
                         boolean antiAlias)
    {
        drawLine(x0, y0, z0, 1.,
                 x1, y1, z1, 1.,
                 antiAlias);
    } // drawLine
    public void drawPoint(double x, double y, double z, double w, int nPixels)
    {
        double q[] = new double[3];
        double depth = xform(x,y,z,w, q); // TODO: don't divide by w!
        if (depth <= 0.)
            return; // culled by eye plane

        super.drawPoint(q[0], q[1], nPixels);
    }
    public void drawPoint(double x, double y, double z, int nPixels)
    {
        drawPoint(x, y, z, 1., nPixels);
    }
    public void drawString(String s, double x, double y, double z, double w,
                                     double xJustify, // -1,0,1 -> L,C,R
                                     double yJustify) // -1,0,1 -> T,C,B
    {
        double q[] = new double[3];
        xform(x,y,z,w, q);
        super.drawString(s, q[0], q[1], xJustify, yJustify);
    }

    public double xform(double x, double y, double z, double w, double out[/*2 or 3 or 4*/])
    {
        CHECK_GE(w, 0.); // shouldn't have any inputs that violate this, any more, currently... although we might in the future

        // this gets called zillions of times, so use scratch arrays...
        double out4[] = scratch0;
        xformNoDivide(x,y,z,w, out4);
        double wOut = out4[3];
        if (wOut == 1.)
            VecMath.copyvec(out.length, out, out4);
        else
            VecMath.vxs(out.length, out, out4, 1./wOut);
        return wOut;
    }
    // trying to move towards more legit homogeneous methods
    public void xformNoDivide(double x, double y, double z, double w, double out4[/*4*/])
    {
        FORI (i, 4)
            out4[i] = x*xformMat[0][i]
                    + y*xformMat[1][i]
                    + z*xformMat[2][i]
                    + w*xformMat[3][i];
    }

    //
    // Utility function to clip x/w,y/w,z/w to [-1,1]x[-1,1]x[-1,1] or [-1,1]x[-1,1]x[-inf,inf]
    // or whatever, in homogeneous space.
    // Original segment endpoints are p0=p+t0*dir, p1=p+t1*dir.
    // Returns clipped t0,t1 (with t1<t0 meaning the line got completely clipped away).
    // Actually works in any number of dimensions.
    // TODO: this could actually go into VecMath?  Maybe?
    //
    private void clipToBoxHomo(double p[],   // some reference point on the line
                               double dir[], // not necessarily unit, can even be zero
                               double t0, double t1, // t0>t1 means clipped away
                               double clipBounds[/*2 (for just x,y clip) or 3 (for near/far as well)*/][/*2*/],
                               double answer_t0_t1[]) // answer goes here
    {
        /*
        System.out.println("    in clipToBoxHomo");
        PRINTVEC(p);
        PRINTVEC(dir);
        PRINT(t0);
        PRINT(t1);
        PRINTMAT(clipBounds);
        */
        if (t0 <= t1)
        {
            int nDims = p.length;
            CHECK_EQ(nDims, dir.length);

            double pw = p[nDims-1];
            double dirw = dir[nDims-1];
            double w0 = pw + t0 * dirw; // w coord of clipped p0 so far
            double w1 = pw + t1 * dirw; // w coord of clipped p1 so far
            FORI (iDim, clipBounds.length)
            {
                double px = p[iDim];
                double dirx = dir[iDim];
                double x0 = px + t0 * dirx; // iDim'th coord of clipped p0 so far
                double x1 = px + t1 * dirx; // iDim'th coord of clipped p1 so far
                double clip0 = clipBounds[iDim][0]; // typically -1, for 90 degree fov
                double clip1 = clipBounds[iDim][1]; // typically 1, for 90 degree fov

                //
                // test against face with normal (0,...,0,-1,0,...,0,clip1)
                //
                if (x0 <= clip1*w0 && x1 <= clip1*w1)
                {
                    // both in or on boundary; retain the whole thing
                }
                else if (x0 >= clip1*w0 && x1 >= clip1*w1)
                {
                    // both out or on boundary; clipped away!
                    // return an inverted interval.
                    t0 = 1.;
                    t1 = 0.;
                    break;
                }
                else
                {
                    // endpoints lie on strictly opposite sides of the face; clip.
                    double t = (clip1*pw-px) / (dirx-clip1*dirw);
                    if (x0 < clip1*w0)
                    {
                        // t0 is inside, t1 is outside and gets clipped
                        t1 = t;
                        w1 = pw + t1 * dirw;
                        x1 = px + t1 * dirx;
                    }
                    else
                    {
                        // t1 is inside, t0 is outside and gets clipped
                        t0 = t;
                        w0 = pw + t0 * dirw;
                        x0 = px + t0 * dirx;
                    }
                }

                //
                // test against face with normal (0,...,0,1,0,...,0,clip0)
                //
                if (x0 >= clip0*w0 && x1 >= clip0*w1)
                {
                    // both in or on boundary; retain the whole thing
                }
                else if (x0 <= clip0*w0 && x1 <= clip0*w1)
                {
                    // both out or on boundary; clipped away!
                    // return an inverted interval.
                    t0 = 1.;
                    t1 = 0.;
                    break;
                }
                else
                {
                    // endpoints lie on strictly opposite sides of the face; clip.
                    double t = (clip0*pw-px) / (dirx-clip0*dirw);
                    if (x0 > clip0*w0)
                    {
                        // t0 is inside, t1 is outside and gets clipped
                        t1 = t;
                        w1 = pw + t1 * dirw;
                        // (no need to update x1; we're done with it)
                    }
                    else
                    {
                        // t1 is inside, t0 is outside and gets clipped
                        t0 = t;
                        w0 = pw + t0 * dirw;
                        // (no need to update x0; we're done with it)
                    }
                }
            } // FORI(iDim, nDims)
        }
        answer_t0_t1[0] = t0;
        answer_t0_t1[1] = t1;
        /*
        PRINT(t0);
        PRINT(t1);
        System.out.println("    out clipToBoxHomo");
        */
    } // clipToBoxHomo

    private MyGraphics mg;
    private double clipBounds[][];
    private double xformMat[][]; // 3d-to-2d xform (actually produces 3d points)

    private double scratch0[] = new double[4];
    private double scratch1[] = new double[4];
    private double scratch2[] = new double[4];
    private double scratch3[] = new double[2];

} // class MyGraphics3D