First commit

4 files changed, 187 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
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+++ b/.gitignore
@@ -0,0 +1,3 @@
+a.out
+*.o
+expvc
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..f53dfc5
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,12 @@
+.POSIX:
+CFLAGS += -std=c99
+CFLAGS += -Wall
+LDLIBS += -lm
+BIN = expvc
+
+all: $(BIN)
+
+expvc: expvc.c
+
+clean:
+	rm -rf $(BIN)
diff --git a/README.md b/README.md
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index 0000000..78c6bcf
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+++ b/README.md
@@ -0,0 +1,13 @@
+# Minecraft calculators (mcal)
+
+This repository contains codes for:
+
+* `expvc`: Explosion entity velocity and damage calculator.
+
+## Compile
+
+Just `make(1)`. How to build on Windows is left as an exercise to the reader.
+
+## License
+
+WTFPL
diff --git a/expvc.c b/expvc.c
new file mode 100644
index 0000000..7cd3af8
--- /dev/null
+++ b/expvc.c
@@ -0,0 +1,159 @@
+/*
+ * Explosion entity velocity and damage calculator.
+ *
+ * @1.17.1
+ *
+ */
+#include <string.h>
+#include <stdio.h>
+#include <assert.h>
+#include <math.h>
+
+struct vec3d {
+	double x;
+	double y;
+	double z;
+};
+
+static int vec3d_parse(char *in, struct vec3d *out)
+{
+	int i = 0;
+	char *p = strtok(in, ",");
+	while (p != NULL)
+	{
+		double *ptr;
+		switch (i ++)
+		{
+			case 0:
+				ptr = &out->x;
+				break;
+			case 1:
+				ptr = &out->y;
+				break;
+			case 2:
+				ptr = &out->z;
+				break;
+			default:
+				assert(0);
+				break;
+		}
+		sscanf(p, "%lf", ptr);
+		p = strtok(NULL, ",");
+	}
+	if (i != 3)
+	{
+		fprintf(stderr, "Invalid Vec3D: %s. Example: -1,1,1.\n", in);
+		return 64;
+	}
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	struct vec3d tnt = { 0.0, 0.0, 0.0 };
+	struct vec3d entity = { 0.0, 0.0, 0.0 };
+	struct vec3d velocity = { 0.0, 0.0, 0.0 };
+	double entity_eye_y = 0.0;
+	int is_tnt = 1;
+	double power = 4.0;
+	double exposure = 1.0;
+	if (argc <= 1)
+	{
+		goto usage;
+usage:
+		fprintf(stderr, "Usage: %s -t 0,0,0 -e 0,0,0 [-v 0,0,0]\n"
+				"\n"
+				"Options:\n"
+				"\t-t  vec3d\tTNT entity coords [Mandatory]\n"
+				"\t-e  vec3d\tTarget entity coords [Mandatory]\n"
+				"\t-p  double\tExplosion power [Optional, defaults to 4.0 (TNT)]\n"
+				"\t-ey vec3d\tTarget entity eye Y [Optional if the target is a TNT]\n"
+				"\t-v  vec3d\tTarget entity initial velocity [Optional, defaults to 0,0,0]\n"
+				"\t-x  double\tExposure of explosion. Percentage. 1.0 if no blocks blocking the ray. [Optional, defaults to 1.0]\n"
+				"\t-h\t\tPrint usage to stderr\n"
+				"\n"
+				"Vec3D Format: x,y,z. No spaces or brackets allowed.\n", argv[0]);
+		return 64;
+	}
+	int r = 0;
+	for (int i = 1; i < argc; i ++)
+	{
+		const char *arg = argv[i];
+		if (!strcmp("-h", arg)) goto usage;
+		if (i == argc - 1)
+		{
+			fprintf(stderr, "%s requires an argument.\n", arg);
+			goto usage;
+		}
+		char *val = argv[++i];
+		if (!strcmp("-t", arg)) { if ((r = vec3d_parse(val, &tnt))) return r; }
+		else if (!strcmp("-e", arg)) { if ((r = vec3d_parse(val, &entity))) return r; }
+		else if (!strcmp("-v", arg)) { if ((r = vec3d_parse(val, &velocity))) return r; }
+		else if (!strcmp("-ey", arg))
+		{
+			sscanf(val, "%lf", &entity_eye_y);
+			is_tnt = 0;
+		}
+		else if (!strcmp("-p", arg)) sscanf(val, "%lf", &power);
+		else if (!strcmp("-x", arg))
+		{
+			sscanf(val, "%lf", &exposure);
+			if (exposure < 0.0 || exposure > 1.0)
+			{
+				fprintf(stderr, "Invalid exposure: [0.0, 1.0]\n");
+				goto usage;
+			}
+		}
+		else
+		{
+			fprintf(stderr, "Unknown argument: %s\n", arg);
+			goto usage;
+		}
+	}
+	printf("(%.5f, %.5f, %.5f) -> %.2f -> %c(%.5f, %.5f, %.5f)\n",
+			tnt.x,
+			tnt.y,
+			tnt.z,
+			power,
+			is_tnt ? 'T' : 'E',
+			entity.x,
+			entity.y,
+			entity.z);
+	double power2 = 2.0 * power;
+	double xx = entity.x - tnt.x;
+	double zz = entity.z - tnt.z;
+	double yy = (is_tnt ? entity.y : entity_eye_y) - tnt.y;
+	double dist = sqrt(xx * xx + (entity.y - tnt.y) * (entity.y - tnt.y) + zz * zz);
+	printf("Square distance: %.5f\n", dist);
+	if (dist / power2 > 1)
+	{
+		printf("Not affected, to too far. (Square distance = %.5f).\n", dist);
+		return 0;
+	}
+	printf("Delta distance: %.5f, %.5f, %.5f\n", xx, yy, zz);
+	double dist_eye_y = sqrt(xx * xx + yy * yy + zz * zz);
+	if (dist_eye_y == 0)
+	{
+		printf("Not affected due to dist_eye_y == 0.\n");
+		return 0;
+	}
+	xx /= dist_eye_y;
+	yy /= dist_eye_y;
+	zz /= dist_eye_y;
+	printf("Delta distance final: %.5f, %.5f, %.5f\n", xx, yy, zz);
+	double accel = (1.0 - (dist / power2)) * exposure;
+	printf("Accel: %.5f\n", accel);
+	int damage = (int) ((accel * accel + accel) / 2.0 * 7.0 * power2 + 1.0);
+	printf("Damage: %d\n", damage);
+	struct vec3d delta_v = {
+		xx * accel,
+		yy * accel,
+		zz * accel
+	};
+	printf("Delta velocity: (%.5f, %.5f, %.5f)\n", delta_v.x, delta_v.y, delta_v.z);
+	velocity.x += delta_v.x;
+	velocity.y += delta_v.y;
+	velocity.z += delta_v.z;
+	printf("Final velocity: (%.5f, %.5f, %.5f)\n", velocity.x, velocity.y, velocity.z);
+	return 0;
+}