From 13ff21bb228d131b0b48f81ad57629a4d4756bc2 Mon Sep 17 00:00:00 2001
From: Simon Robertshaw <simon@hardwired.org.uk>
Date: Fri, 22 Apr 2011 17:06:09 +0100
Subject: [PATCH] Gravitaaaay (Needs tweeking for performance)

---
 includes/air.h      |  7 +++++++
 includes/graphics.h |  2 ++
 src/air.c           | 47 +++++++++++++++++++++++++++++++++++++++++++++
 src/graphics.c      | 24 +++++++++++++++++++++++
 src/main.c          |  6 ++++--
 src/powder.c        |  6 ++++++
 6 files changed, 90 insertions(+), 2 deletions(-)

diff --git a/includes/air.h b/includes/air.h
index d9e04f631..eda397640 100644
--- a/includes/air.h
+++ b/includes/air.h
@@ -2,6 +2,11 @@
 #define AIR_H
 #include "defines.h"
 
+extern float ogravmap[YRES/CELL][XRES/CELL];
+extern float gravmap[YRES/CELL][XRES/CELL];
+extern float gravx[YRES/CELL][XRES/CELL];
+extern float gravy[YRES/CELL][XRES/CELL];
+
 extern float vx[YRES/CELL][XRES/CELL], ovx[YRES/CELL][XRES/CELL];
 extern float vy[YRES/CELL][XRES/CELL], ovy[YRES/CELL][XRES/CELL];
 extern float pv[YRES/CELL][XRES/CELL], opv[YRES/CELL][XRES/CELL];
@@ -16,6 +21,8 @@ extern float kernel[9];
 
 void make_kernel(void);
 
+void update_grav(void);
+
 void update_air(void);
 
 #endif
\ No newline at end of file
diff --git a/includes/graphics.h b/includes/graphics.h
index 31f8c57d4..f17e3f3d3 100644
--- a/includes/graphics.h
+++ b/includes/graphics.h
@@ -100,6 +100,8 @@ void draw_icon(pixel *vid_buf, int x, int y, char ch, int flag);
 
 void draw_air(pixel *vid);
 
+void draw_grav(pixel *vid);
+
 void draw_line(pixel *vid, int x1, int y1, int x2, int y2, int r, int g, int b, int a);
 
 void addpixel(pixel *vid, int x, int y, int r, int g, int b, int a);
diff --git a/src/air.c b/src/air.c
index 8c11f30a9..2947d935c 100644
--- a/src/air.c
+++ b/src/air.c
@@ -4,6 +4,11 @@
 #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];
@@ -29,6 +34,48 @@ void make_kernel(void) //used for velocity
 		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;
diff --git a/src/graphics.c b/src/graphics.c
index b92f12cc4..703e97244 100644
--- a/src/graphics.c
+++ b/src/graphics.c
@@ -1255,6 +1255,30 @@ void draw_air(pixel *vid)
 		}
 }
 
+void draw_grav(pixel *vid)
+{
+	int x, y, i;
+	float nx, ny, dist;
+
+	for (y=0; y<YRES/CELL; y++)
+	{
+		for (x=0; x<XRES/CELL; x++)
+		{
+			if(fabsf(gravx[y][x]) <= 0.001f && fabsf(gravy[y][x]) <= 0.001f)
+				continue;
+			nx = x*CELL;
+			ny = y*CELL;
+			dist = fabsf(gravx[y][x])+fabsf(gravy[y][x]);
+			for(i = 0; i < 4; i++)
+			{
+				nx -= gravx[y][x]*0.5f;
+				ny -= gravy[y][x]*0.5f;
+				addpixel(vid, (int)(nx+0.5f), (int)(ny+0.5f), 255, 255, 255, (int)(dist*20.0f));
+			}
+		}
+	}
+}
+
 void draw_line(pixel *vid, int x1, int y1, int x2, int y2, int r, int g, int b, int a)  //Draws a line
 {
 	int dx, dy, i, sx, sy, check, e, x, y;
diff --git a/src/main.c b/src/main.c
index f1f26bb0e..bbcd5f5e3 100644
--- a/src/main.c
+++ b/src/main.c
@@ -2869,8 +2869,9 @@ int main(int argc, char *argv[])
 			memset(vid_buf, 0, (XRES+BARSIZE)*YRES*PIXELSIZE);
 		}
 #endif
+		draw_grav(vid_buf);
 
-		//Can't be too sure...
+		//Can't be too sure (Limit the cursor size)
 		if (bsx>1180)
 			bsx = 1180;
 		if (bsx<0)
@@ -2881,6 +2882,7 @@ int main(int argc, char *argv[])
 			bsy = 0;
 		
 		update_particles(vid_buf); //update everything
+		update_grav();
 		draw_parts(vid_buf); //draw particles
 
 		if (cmode==CM_PERS)
@@ -3577,7 +3579,7 @@ int main(int argc, char *argv[])
 				sprintf(heattext, "Empty, Pressure: %3.2f", pv[(y/sdl_scale)/CELL][(x/sdl_scale)/CELL]);
 				if (DEBUG_MODE)
 				{
-					sprintf(coordtext, "X:%d Y:%d", x/sdl_scale, y/sdl_scale);
+					sprintf(coordtext, "X:%d Y:%d. GX: %.2f GY: %.2f", x/sdl_scale, y/sdl_scale, gravx[(y/sdl_scale)/CELL][(x/sdl_scale)/CELL], gravy[(y/sdl_scale)/CELL][(x/sdl_scale)/CELL]);
 				}
 			}
 		}
diff --git a/src/powder.c b/src/powder.c
index 7dd1ad8aa..e697f2444 100644
--- a/src/powder.c
+++ b/src/powder.c
@@ -1463,6 +1463,12 @@ void update_particles_i(pixel *vid, int start, int inc)
 				pGravX = ptypes[t].gravity * ((float)(x - XCNTR) / pGravD);
 				pGravY = ptypes[t].gravity * ((float)(y - YCNTR) / pGravD);
 			}
+			//Get some gravity from the gravity map
+			if(!(ptypes[t].properties & TYPE_SOLID))
+			{
+				pGravX += gravx[y/CELL][x/CELL];
+				pGravY += gravy[y/CELL][x/CELL];
+			}
 			//velocity updates for the particle
 			parts[i].vx *= ptypes[t].loss;
 			parts[i].vy *= ptypes[t].loss;