The-Powder-Toy/src/air.c

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

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_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));
}
}