ball.c

[Game.Programming].Academic - Graphics Gems (6 books source code)

/***** Ball.c *****/
/* Ken Shoemake, 1993 */
#include <gl/gl.h>
#include "Ball.h"
#include "BallMath.h"

#define LG_NSEGS 4
#define NSEGS (1<<LG_NSEGS)
#define RIMCOLOR()    RGBcolor(255, 255, 255)
#define FARCOLOR()    RGBcolor(195, 127, 31)
#define NEARCOLOR()   RGBcolor(255, 255, 63)
#define DRAGCOLOR()   RGBcolor(127, 255, 255)
#define RESCOLOR()    RGBcolor(195, 31, 31)

HMatrix mId = {{1,0,0,0},{0,1,0,0},{0,0,1,0},{0,0,0,1}};
float otherAxis[][4] = {{-0.48, 0.80, 0.36, 1}};

/* Establish reasonable initial values for controller. */
void Ball_Init(BallData *ball)
{
    int i;
    ball->center = qOne;
    ball->radius = 1.0;
    ball->vDown = ball->vNow = qOne;
    ball->qDown = ball->qNow = qOne;
    for (i=15; i>=0; i--)
	((float *)ball->mNow)[i] = ((float *)ball->mDown)[i] = ((float *)mId)[i];
    ball->showResult = ball->dragging = FALSE;
    ball->axisSet = NoAxes;
    ball->sets[CameraAxes] = mId[X]; ball->setSizes[CameraAxes] = 3;
    ball->sets[BodyAxes] = ball->mDown[X]; ball->setSizes[BodyAxes] = 3;
    ball->sets[OtherAxes] = otherAxis[X]; ball->setSizes[OtherAxes] = 1;
}

/* Set the center and size of the controller. */
void Ball_Place(BallData *ball, HVect center, double radius)
{
    ball->center = center;
    ball->radius = radius;
}

/* Incorporate new mouse position. */
void Ball_Mouse(BallData *ball, HVect vNow)
{
    ball->vNow = vNow;
}

/* Choose a constraint set, or none. */
void Ball_UseSet(BallData *ball, AxisSet axisSet)
{
    if (!ball->dragging) ball->axisSet = axisSet;
}

/* Begin drawing arc for all drags combined. */
void Ball_ShowResult(BallData *ball)
{
    ball->showResult = TRUE;
}

/* Stop drawing arc for all drags combined. */
void Ball_HideResult(BallData *ball)
{
    ball->showResult = FALSE;
}

/* Using vDown, vNow, dragging, and axisSet, compute rotation etc. */
void Ball_Update(BallData *ball)
{
    int i, setSize = ball->setSizes[ball->axisSet];
    HVect *set = (HVect *)(ball->sets[ball->axisSet]);
    ball->vFrom = MouseOnSphere(ball->vDown, ball->center, ball->radius);
    ball->vTo = MouseOnSphere(ball->vNow, ball->center, ball->radius);
    if (ball->dragging) {
	if (ball->axisSet!=NoAxes) {
	    ball->vFrom = ConstrainToAxis(ball->vFrom, set[ball->axisIndex]);
	    ball->vTo = ConstrainToAxis(ball->vTo, set[ball->axisIndex]);
	}
	ball->qDrag = Qt_FromBallPoints(ball->vFrom, ball->vTo);
	ball->qNow = Qt_Mul(ball->qDrag, ball->qDown);
    } else {
	if (ball->axisSet!=NoAxes) {
	    ball->axisIndex = NearestConstraintAxis(ball->vTo, set, setSize);
	}
    }
    Qt_ToBallPoints(ball->qDown, &ball->vrFrom, &ball->vrTo);
    Qt_ToMatrix(Qt_Conj(ball->qNow), ball->mNow); /* Gives transpose for GL. */
}

/* Return rotation matrix defined by controller use. */
void Ball_Value(BallData *ball, HMatrix mNow)
{
    int i;
    for (i=15; i>=0; i--) ((float *)mNow)[i] = ((float *)ball->mNow)[i];
}


/* Begin drag sequence. */
void Ball_BeginDrag(BallData *ball)
{
    ball->dragging = TRUE;
    ball->vDown = ball->vNow;
}

/* Stop drag sequence. */
void Ball_EndDrag(BallData *ball)
{
    int i;
    ball->dragging = FALSE;
    ball->qDown = ball->qNow;
    for (i=15; i>=0; i--)
	((float *)ball->mDown)[i] = ((float *)ball->mNow)[i];
}

/* Draw the controller with all its arcs. */
void Ball_Draw(BallData *ball)
{
    float r = ball->radius;
    pushmatrix();
    loadmatrix(mId);
    ortho2(-1.0, 1.0, -1.0, 1.0);
    RIMCOLOR();
    scale(r, r, r);
    circ(0.0, 0.0, 1.0);
    Ball_DrawResultArc(ball);
    Ball_DrawConstraints(ball);
    Ball_DrawDragArc(ball);
    popmatrix();
}

/* Draw an arc defined by its ends. */
void DrawAnyArc(HVect vFrom, HVect vTo)
{
    int i;
    HVect pts[NSEGS+1];
    double dot;
    pts[0] = vFrom;
    pts[1] = pts[NSEGS] = vTo;
    for (i=0; i<LG_NSEGS; i++) pts[1] = V3_Bisect(pts[0], pts[1]);
    dot = 2.0*V3_Dot(pts[0], pts[1]);
    for (i=2; i<NSEGS; i++) {
	pts[i] = V3_Sub(V3_Scale(pts[i-1], dot), pts[i-2]);
    }
    bgnline();
    for (i=0; i<=NSEGS; i++)
	v3f((float *)&pts[i]);
    endline();
}

/* Draw the arc of a semi-circle defined by its axis. */
void DrawHalfArc(HVect n)
{
    HVect p, m;
    p.z = 0;
    if (n.z != 1.0) {
	p.x = n.y; p.y = -n.x;
	p = V3_Unit(p);
    } else {
	p.x = 0; p.y = 1;
    }
    m = V3_Cross(p, n);
    DrawAnyArc(p, m);
    DrawAnyArc(m, V3_Negate(p));
}

/* Draw all constraint arcs. */
void Ball_DrawConstraints(BallData *ball)
{
    ConstraintSet set;
    HVect axis;
    int j, axisI, setSize = ball->setSizes[ball->axisSet];
    if (ball->axisSet==NoAxes) return;
    set = ball->sets[ball->axisSet];
    for (axisI=0; axisI<setSize; axisI++) {
	if (ball->axisIndex!=axisI) {
	    if (ball->dragging) continue;
	    FARCOLOR();
	} else NEARCOLOR();
	axis = *(HVect *)&set[4*axisI];
	if (axis.z==1.0) {
	    circ(0.0, 0.0, 1.0);
	} else {
	    DrawHalfArc(axis);
	}
    }
}

/* Draw "rubber band" arc during dragging. */
void Ball_DrawDragArc(BallData *ball)
{
    DRAGCOLOR();
    if (ball->dragging) DrawAnyArc(ball->vFrom, ball->vTo);
}

/* Draw arc for result of all drags. */
void Ball_DrawResultArc(BallData *ball)
{
    RESCOLOR();
    if (ball->showResult) DrawAnyArc(ball->vrFrom, ball->vrTo);
}