155 lines
3.9 KiB
HolyC
155 lines
3.9 KiB
HolyC
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/*Uses $LK,"fixed-point",A="FI:::/Demo/Lectures/FixedPoint.HC"$ arithmetic
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because it used to be faster than floating
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point. See $LK,"::/Demo/Lectures/FixedPoint.HC"$.
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The decimal place is between
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bits 31 and 32.
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*/
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#define BALLS_NUM 64
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#define BALL_RADIUS 5
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I64 ball_x[BALLS_NUM],ball_y[BALLS_NUM],
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ball_velocity_x[BALLS_NUM],ball_velocity_y[BALLS_NUM];
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U0 DrawIt(CTask *,CDC *dc)
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{
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I64 i;
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dc->color=RED;
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for (i=0;i<BALLS_NUM;i++)
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GrCircle(dc,ball_x[i].i32[1],ball_y[i].i32[1],BALL_RADIUS);
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}
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/****
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$SP,"",BI=1$
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Initial and final velocity vects
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with normal and tangential components.
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All masses are ident, so they
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have been dropped from the equations.
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Conservation of Momentum:
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V1$SY,3$it$SY,0$+V2$SY,3$it$SY,0$=V1$SY,3$ft$SY,0$+V2$SY,3$ft$SY,0$
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V1$SY,3$in$SY,0$+V2$SY,3$in$SY,0$=V1$SY,3$fn$SY,0$+V2$SY,3$fn$SY,0$
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Conservation of Energy:
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|V1$SY,3$i$SY,0$|$SY,-3$2$SY,0$+|V2$SY,3$i$SY,0$|$SY,-3$2$SY,0$=|V1$SY,3$f$SY,0$|$SY,-3$2$SY,0$+|V2$SY,3$f$SY,0$|$SY,-3$2$SY,0$
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****/
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U0 AnimateTask(I64)
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{
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CTask *task=Fs->parent_task;
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I64 i,j,h,v,distdist,
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dia=(2*BALL_RADIUS)<<32,
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diadia=SqrI64(2*BALL_RADIUS)<<32,
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delta_x,delta_y,v_t1,v_n1,v_t2,v_n2;
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F64 dist;
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while (TRUE) {
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h=task->pix_width;
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v=task->pix_height;
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for (i=0;i<BALLS_NUM;i++) {
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ball_x[i]+=ball_velocity_x[i];
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ball_y[i]+=ball_velocity_y[i];
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if (ball_x[i]<BALL_RADIUS<<32) {
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ball_velocity_x[i]*=-1;
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ball_x[i]=BALL_RADIUS<<32;
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}
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if (ball_x[i]>=(h-BALL_RADIUS)<<32) {
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ball_velocity_x[i]*=-1;
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ball_x[i]=(h-BALL_RADIUS)<<32;
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}
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if (ball_y[i]<BALL_RADIUS<<32) {
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ball_velocity_y[i]*=-1;
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ball_y[i]=BALL_RADIUS<<32;
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}
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if (ball_y[i]>=(v-BALL_RADIUS)<<32) {
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ball_velocity_y[i]*=-1;
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ball_y[i]=(v-BALL_RADIUS)<<32;
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}
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}
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for (i=0;i<BALLS_NUM;i++) {
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for (j=i+1;j<BALLS_NUM;j++) {
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delta_x=ball_x[i]-ball_x[j];
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delta_y=ball_y[i]-ball_y[j];
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//We shift 16 because multiplying
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//two 32 shifted would yield 64 shifted
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//and we want a 32 shifted res.
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distdist=SqrI64(delta_x>>16)+SqrI64(delta_y>>16);
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//We work with square instead of sqrt
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//to avoid unnecessarily calculating
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//square heads (They are slow.)
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if (distdist && distdist<=diadia) {
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dist=Sqrt(distdist); //shifted 16 bits
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delta_x/=dist; //shifted 16
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delta_y/=dist;
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v_t1=(ball_velocity_x[i]>>16*delta_y-
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ball_velocity_y[i]>>16*delta_x)>>16;
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v_n1=(ball_velocity_x[i]>>16*delta_x+
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ball_velocity_y[i]>>16*delta_y)>>16;
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v_t2=(ball_velocity_x[j]>>16*delta_y-
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ball_velocity_y[j]>>16*delta_x)>>16;
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v_n2=(ball_velocity_x[j]>>16*delta_x+
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ball_velocity_y[j]>>16*delta_y)>>16;
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if (ball_velocity_x[i]>>16*ball_velocity_x[j]>>16+
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ball_velocity_y[i]>>16*ball_velocity_y[j]>>16<=0) {
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ball_velocity_x[i]= v_t1*delta_y-v_n1*delta_x;
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ball_velocity_y[i]=-v_t1*delta_x-v_n1*delta_y;
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ball_velocity_x[j]= v_t2*delta_y-v_n2*delta_x;
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ball_velocity_y[j]=-v_t2*delta_x-v_n2*delta_y;
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} else {
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ball_velocity_x[i]= v_t1*delta_y+v_n2*delta_x;
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ball_velocity_y[i]=-v_t1*delta_x+v_n2*delta_y;
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ball_velocity_x[j]= v_t2*delta_y+v_n1*delta_x;
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ball_velocity_y[j]=-v_t2*delta_x+v_n1*delta_y;
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}
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//Correct for overlap
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dist=0x10000+(dia/0x10000-dist)/2;
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ball_x[i]+=dist*delta_x;
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ball_y[i]+=dist*delta_y;
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ball_x[j]-=dist*delta_x;
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ball_y[j]-=dist*delta_y;
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}
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}
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}
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Sleep(1);
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}
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}
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U0 Init()
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{
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I64 i;
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for (i=0;i<BALLS_NUM;i++) {
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ball_x[i]=(RandU16%(Fs->pix_width-BALL_RADIUS*2)+BALL_RADIUS)<<32;
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ball_y[i]=(RandU16%(Fs->pix_height-BALL_RADIUS*2)+BALL_RADIUS)<<32;
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ball_velocity_x[i]=RandI32/4;
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ball_velocity_y[i]=RandI32/4;
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}
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}
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U0 Collision()
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{
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SettingsPush; //See $LK,"SettingsPush",A="MN:SettingsPush"$
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Init;
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Fs->animate_task=Spawn(&AnimateTask,NULL,"Animate",,Fs);
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DocCursor;
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DocClear;
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Fs->draw_it=&DrawIt;
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GetChar;
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SettingsPop;
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}
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Collision;
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W d <EFBFBD><EFBFBD><EFBFBD><EFBFBD> <EFBFBD> r <EFBFBD> <EFBFBD><EFBFBD><EFBFBD><EFBFBD>r <EFBFBD> <EFBFBD> <EFBFBD><EFBFBD><EFBFBD><EFBFBD>v_t <EFBFBD> v_n
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