在仿真中实现碰撞响应

 #include<stdio.h>
 #include<math.h>
 #include<stdlib.h>

 int main() {

     FILE *fp; 
     FILE *fr;

     //Declare and initialize all variables to be used
     float ax = 0, ay = 0, x = 0, y = 0, vx = 0, vy = 0; 
     float time = 0, deltaTime = .001; 
     float vyImpact = 0, vxImpact = 0, xImpact = 0; 

     float old_y = 0,  old_x = 0, old_vy = 0, old_vx = 0;
     float deltaTime2 = 0,  deltaTime3 = 0;

     int numBounces = 0;

     //Coefficient of Restitution; epsilon = ex = ey
     float ex = .5;
     float ey = .5;

     fr = fopen(\"input_data.txt\", \"rt\"); //Open file for reading

     fp = fopen( \"output_data.txt\", \"w\" ); // Open file for writing

     if(fr == NULL){ printf(\"File not found\");} //if text file is not in directory...

     if(fp == NULL){ printf(\"File not found\");} //if text file is not in directory...

     fscanf(fr, \"ax: %f ay: %f x: %f y: %f vx: %f vy: %f\\n\", &ax, &ay, &x, &y, &vx, &vy); 

     while (numBounces < 9) {

          //time = time + deltaTime
          time = time + deltaTime;

          //velocity[new] = velocity[old] + acc * deltaTime
          vx = vx + ax*deltaTime;
          vy = vy + ay*deltaTime;

          //position[new] = position[old] + velocity*deltaTime + .5*acc*(deltaTime)^2
          x = x + vx*deltaTime + (.5*ax*deltaTime*deltaTime);
          y = y + vy*deltaTime + (.5*ay*deltaTime*deltaTime);  

          fprintf(fp, \"%f\\t%f\\t%f\\t%f\\t%f\\t%f\\t%f\\t\\n\", ax, ay, x, y, vx, vy, time);

               //Collision occurs; implement collision response
              if (y < 0) {

                   //\"Undo\" values for y, x, and velocity
                   old_y = y - vy*deltaTime - (.5*ay*deltaTime*deltaTime); 
                   old_x = x - vx*deltaTime - (.5*ax*deltaTime*deltaTime); 
                   old_vy = vy - ay*deltaTime;
                   old_vx = vx - ax*deltaTime; 

                   //Calculate time of collision
                   deltaTime2 = (-old_y + sqrt((old_y*old_y) - 2*ay*old_y)) / (ay);
                   printf(\"Time of Collision = %f\\n\", time - deltaTime2); 

                   //Calculate velocity and x position at collsion
                   vyImpact = old_vy + ay*deltaTime2;
                   vxImpact = old_vx + ax*deltaTime2;
                   xImpact = old_x + old_vx*deltaTime2 + .5*ax*(deltaTime2*deltaTime2);

                   //Calculate new time for when ball bounces
                   deltaTime3 = deltaTime - deltaTime2;

                   //Calculate new x and y position and velocity for when ball bounces
                   x = xImpact + (ex)*vxImpact*deltaTime3 + .5*ax*(deltaTime3*deltaTime3);
                   y = 0 + (-ey)*vyImpact*deltaTime3 + .5*ay*(deltaTime3*deltaTime3);
                   vy = (-ey)*vyImpact + ay*deltaTime3;
                   vx = (ex)*vxImpact + ax*deltaTime3; 

                   numBounces++; 
                   printf(\"Number of Bounce(s) = %d\\n\", numBounces);


                   fprintf(fp, \"%f\\t%f\\t%f\\t%f\\t%f\\t%f\\t%f\\t\\n\", ax, ay, x, y, vx, vy, time);

               }
     }

     fclose(fp); //Close output file
     fclose(fr); //Close input file

     //system (\"PAUSE\"); 
     return 0;
  }