The-Powder-Toy/src/air.c

#include <math.h>
#include <air.h>
#include <powder.h>
#include <defines.h>
float kernel[9];

float ogravmap[YRES/CELL][XRES/CELL];
float gravmap[YRES/CELL][XRES/CELL];
float gravx[YRES/CELL][XRES/CELL];
float gravy[YRES/CELL][XRES/CELL];

float vx[YRES/CELL][XRES/CELL], ovx[YRES/CELL][XRES/CELL];
float vy[YRES/CELL][XRES/CELL], ovy[YRES/CELL][XRES/CELL];
float pv[YRES/CELL][XRES/CELL], opv[YRES/CELL][XRES/CELL];

float cb_vx[YRES/CELL][XRES/CELL], cb_ovx[YRES/CELL][XRES/CELL];
float cb_vy[YRES/CELL][XRES/CELL], cb_ovy[YRES/CELL][XRES/CELL];
float cb_pv[YRES/CELL][XRES/CELL], cb_opv[YRES/CELL][XRES/CELL];

float fvx[YRES/CELL][XRES/CELL], fvy[YRES/CELL][XRES/CELL];

void make_kernel(void) //used for velocity
{
	int i, j;
	float s = 0.0f;
	for (j=-1; j<2; j++)
		for (i=-1; i<2; i++)
		{
			kernel[(i+1)+3*(j+1)] = expf(-2.0f*(i*i+j*j));
			s += kernel[(i+1)+3*(j+1)];
		}
	s = 1.0f / s;
	for (j=-1; j<2; j++)
		for (i=-1; i<2; i++)
			kernel[(i+1)+3*(j+1)] *= s;
}
void update_grav(void)
{
	int x, y, i, j, changed = 0;
	//Find any changed cells
	for (i=0; i<YRES/CELL; i++)
	{
		if(changed)
			break;
		for (j=0; j<XRES/CELL; j++)
		{
			if(ogravmap[i][j]!=gravmap[i][j]){
				changed = 1;
				break;
			}
		}
	}
	if(changed)
	{
		memset(gravy, 0, sizeof(gravy));
		memset(gravx, 0, sizeof(gravx));
		for (i=0; i<YRES/CELL; i++)
		{
			for (j=0; j<XRES/CELL; j++)
			{
				if(gravmap[i][j]>0.0f) //Only calculate with populated or changed cells.
					for (y=0; y<YRES/CELL; y++)
					{
						for (x=0; x<XRES/CELL; x++)
						{
							if(x == j && y == i)//Ensure it doesn't calculate with itself
								continue;
							float distance = sqrt(pow(j - x, 2) + pow(i - y, 2));
							gravx[y][x] += M_GRAV*gravmap[i][j]*(j - x)/pow(distance, 3);
							gravy[y][x] += M_GRAV*gravmap[i][j]*(i - y)/pow(distance, 3);
						}
					}
			}
		}
	}
	memcpy(ogravmap, gravmap, sizeof(gravmap));
	memset(gravmap, 0, sizeof(gravmap));
}
void update_air(void)
{
	int x, y, i, j;
	float dp, dx, dy, f, tx, ty;

	if (airMode != 4) { //airMode 4 is no air/pressure update

		for (i=0; i<YRES/CELL; i++) //reduces pressure/velocity on the edges every frame
		{
			pv[i][0] = pv[i][0]*0.8f;
			pv[i][1] = pv[i][1]*0.8f;
			pv[i][2] = pv[i][2]*0.8f;
			pv[i][XRES/CELL-2] = pv[i][XRES/CELL-2]*0.8f;
			pv[i][XRES/CELL-1] = pv[i][XRES/CELL-1]*0.8f;
			vx[i][0] = vx[i][1]*0.9f;
			vx[i][1] = vx[i][2]*0.9f;
			vx[i][XRES/CELL-2] = vx[i][XRES/CELL-3]*0.9f;
			vx[i][XRES/CELL-1] = vx[i][XRES/CELL-2]*0.9f;
			vy[i][0] = vy[i][1]*0.9f;
			vy[i][1] = vy[i][2]*0.9f;
			vy[i][XRES/CELL-2] = vy[i][XRES/CELL-3]*0.9f;
			vy[i][XRES/CELL-1] = vy[i][XRES/CELL-2]*0.9f;
		}
		for (i=0; i<XRES/CELL; i++) //reduces pressure/velocity on the edges every frame
		{
			pv[0][i] = pv[0][i]*0.8f;
			pv[1][i] = pv[1][i]*0.8f;
			pv[2][i] = pv[2][i]*0.8f;
			pv[YRES/CELL-2][i] = pv[YRES/CELL-2][i]*0.8f;
			pv[YRES/CELL-1][i] = pv[YRES/CELL-1][i]*0.8f;
			vx[0][i] = vx[1][i]*0.9f;
			vx[1][i] = vx[2][i]*0.9f;
			vx[YRES/CELL-2][i] = vx[YRES/CELL-3][i]*0.9f;
			vx[YRES/CELL-1][i] = vx[YRES/CELL-2][i]*0.9f;
			vy[0][i] = vy[1][i]*0.9f;
			vy[1][i] = vy[2][i]*0.9f;
			vy[YRES/CELL-2][i] = vy[YRES/CELL-3][i]*0.9f;
			vy[YRES/CELL-1][i] = vy[YRES/CELL-2][i]*0.9f;
		}

		for (j=1; j<YRES/CELL; j++) //clear some velocities near walls
		{
			for (i=1; i<XRES/CELL; i++)
			{
				if (bmap[j][i]==WL_WALL || bmap[j][i]==WL_WALLELEC || (bmap[j][i]==WL_EWALL && !emap[j][i]))
				{
					vx[j][i] = 0.0f;
					vx[j][i-1] = 0.0f;
					vy[j][i] = 0.0f;
					vy[j-1][i] = 0.0f;
				}
			}
		}

		for (y=1; y<YRES/CELL; y++) //pressure adjustments from velocity
			for (x=1; x<XRES/CELL; x++)
			{
				dp = 0.0f;
				dp += vx[y][x-1] - vx[y][x];
				dp += vy[y-1][x] - vy[y][x];
				pv[y][x] *= AIR_PLOSS;
				pv[y][x] += dp*AIR_TSTEPP;
			}

		for (y=0; y<YRES/CELL-1; y++) //velocity adjustments from pressure
			for (x=0; x<XRES/CELL-1; x++)
			{
				dx = dy = 0.0f;
				dx += pv[y][x] - pv[y][x+1];
				dy += pv[y][x] - pv[y+1][x];
				vx[y][x] *= AIR_VLOSS;
				vy[y][x] *= AIR_VLOSS;
				vx[y][x] += dx*AIR_TSTEPV;
				vy[y][x] += dy*AIR_TSTEPV;
				if (bmap[y][x]==WL_WALL || bmap[y][x+1]==WL_WALL ||
				        bmap[y][x]==WL_WALLELEC || bmap[y][x+1]==WL_WALLELEC ||
				        (bmap[y][x]==WL_EWALL && !emap[y][x]) ||
				        (bmap[y][x+1]==WL_EWALL && !emap[y][x+1]))
					vx[y][x] = 0;
				if (bmap[y][x]==WL_WALL || bmap[y+1][x]==WL_WALL ||
				        bmap[y][x]==WL_WALLELEC || bmap[y+1][x]==WL_WALLELEC ||
				        (bmap[y][x]==WL_EWALL && !emap[y][x]) ||
				        (bmap[y+1][x]==WL_EWALL && !emap[y+1][x]))
					vy[y][x] = 0;
			}

		for (y=0; y<YRES/CELL; y++) //update velocity and pressure
			for (x=0; x<XRES/CELL; x++)
			{
				dx = 0.0f;
				dy = 0.0f;
				dp = 0.0f;
				for (j=-1; j<2; j++)
					for (i=-1; i<2; i++)
						if (y+j>0 && y+j<YRES/CELL-1 &&
						        x+i>0 && x+i<XRES/CELL-1 &&
						        bmap[y+j][x+i]!=WL_WALL &&
						        bmap[y+j][x+i]!=WL_WALLELEC &&
						        (bmap[y+j][x+i]!=WL_EWALL || emap[y+j][x+i]))
						{
							f = kernel[i+1+(j+1)*3];
							dx += vx[y+j][x+i]*f;
							dy += vy[y+j][x+i]*f;
							dp += pv[y+j][x+i]*f;
						}
						else
						{
							f = kernel[i+1+(j+1)*3];
							dx += vx[y][x]*f;
							dy += vy[y][x]*f;
							dp += pv[y][x]*f;
						}

				tx = x - dx*0.7f;
				ty = y - dy*0.7f;
				i = (int)tx;
				j = (int)ty;
				tx -= i;
				ty -= j;
				if (i>=2 && i<XRES/CELL-3 &&
				        j>=2 && j<YRES/CELL-3)
				{
					dx *= 1.0f - AIR_VADV;
					dy *= 1.0f - AIR_VADV;

					dx += AIR_VADV*(1.0f-tx)*(1.0f-ty)*vx[j][i];
					dy += AIR_VADV*(1.0f-tx)*(1.0f-ty)*vy[j][i];

					dx += AIR_VADV*tx*(1.0f-ty)*vx[j][i+1];
					dy += AIR_VADV*tx*(1.0f-ty)*vy[j][i+1];

					dx += AIR_VADV*(1.0f-tx)*ty*vx[j+1][i];
					dy += AIR_VADV*(1.0f-tx)*ty*vy[j+1][i];

					dx += AIR_VADV*tx*ty*vx[j+1][i+1];
					dy += AIR_VADV*tx*ty*vy[j+1][i+1];
				}

				if (bmap[y][x] == WL_FAN)
				{
					dx += fvx[y][x];
					dy += fvy[y][x];
				}
				// pressure/velocity caps
				if (dp > 256.0f) dp = 256.0f;
				if (dp < -256.0f) dp = -256.0f;
				if (dx > 256.0f) dx = 256.0f;
				if (dx < -256.0f) dx = -256.0f;
				if (dy > 256.0f) dy = 256.0f;
				if (dy < -256.0f) dy = -256.0f;


				switch (airMode)
				{
				default:
				case 0:  //Default
					break;
				case 1:  //0 Pressure
					dp = 0.0f;
					break;
				case 2:  //0 Velocity
					dx = 0.0f;
					dy = 0.0f;
					break;
				case 3: //0 Air
					dx = 0.0f;
					dy = 0.0f;
					dp = 0.0f;
					break;
				case 4: //No Update
					break;
				}

				ovx[y][x] = dx;
				ovy[y][x] = dy;
				opv[y][x] = dp;
			}
		memcpy(vx, ovx, sizeof(vx));
		memcpy(vy, ovy, sizeof(vy));
		memcpy(pv, opv, sizeof(pv));
	}
}