From fcac764d752234a03df536dd408235170394f6ad Mon Sep 17 00:00:00 2001
From: John Tsiombikas <nuclear@mutantstargoat.com>
Date: Mon, 10 Sep 2018 18:44:12 +0300
Subject: [PATCH] hairball screen

---
 src/3dgfx.c    |    5 +-
 src/hairball.c |  226 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/screen.c   |    4 +
 src/vmath.h    |   18 +++++
 4 files changed, 252 insertions(+), 1 deletion(-)
 create mode 100644 src/hairball.c

diff --git a/src/3dgfx.c b/src/3dgfx.c
index a642c1e..c852736 100644
--- a/src/3dgfx.c
+++ b/src/3dgfx.c
@@ -515,7 +515,10 @@ void g3d_draw_indexed(int prim, const struct g3d_vertex *varr, int varr_size,
 			break;
 
 		case 2:
-			/* TODO: draw line */
+			{
+				uint16_t col = PACK_RGB16(pv[0].r, pv[0].g, pv[0].b);
+				draw_line(pv[0].x >> 8, pv[0].y >> 8, pv[1].x >> 8, pv[1].y >> 8, col);
+			}
 			break;
 
 		default:
diff --git a/src/hairball.c b/src/hairball.c
new file mode 100644
index 0000000..40ce53f
--- /dev/null
+++ b/src/hairball.c
@@ -0,0 +1,226 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "demo.h"
+#include "3dgfx.h"
+#include "vmath.h"
+#include "screen.h"
+#include "util.h"
+
+#define NSPAWNPOS	128
+#define SPAWN_RATE	16.0f
+#define GRAV		(-6.0f)
+#define HAIR_LENGTH 32
+
+struct particle {
+	vec3_t pos;
+	vec3_t vel;
+	float r, g, b, a;
+	int life;
+
+	struct particle *next;
+};
+
+struct hairball {
+	vec3_t pos;
+	quat_t rot;
+	float xform[16];
+
+	struct particle *plist[NSPAWNPOS];
+};
+
+static int init(void);
+static void destroy(void);
+static void start(long trans_time);
+static void draw(void);
+static void update_hairball(struct hairball *hb, float dt);
+static void draw_hairball(struct hairball *hb);
+
+static struct particle *palloc(void);
+void pfree(struct particle *p);
+
+
+static struct screen scr = {
+	"hairball",
+	init,
+	destroy,
+	start, 0,
+	draw
+};
+
+static long start_time;
+
+static vec3_t *spawnpos, *spawndir;
+
+static struct hairball hball;
+
+struct screen *hairball_screen(void)
+{
+	return &scr;
+}
+
+static int init(void)
+{
+	int i;
+
+	hball.xform[0] = hball.xform[5] = hball.xform[10] = hball.xform[15] = 1.0f;
+	hball.rot.w = 1.0f;
+
+	if(!(spawnpos = malloc(NSPAWNPOS * sizeof *spawnpos)) ||
+			!(spawndir = malloc(NSPAWNPOS * sizeof *spawndir))) {
+		fprintf(stderr, "failed to allocate spawnpos/dir array\n");
+		return -1;
+	}
+
+	for(i=0; i<NSPAWNPOS; i++) {
+		spawnpos[i] = spawndir[i] = sphrand(1.0f);
+	}
+
+	return 0;
+}
+
+static void destroy(void)
+{
+}
+
+static void start(long trans_time)
+{
+	g3d_matrix_mode(G3D_PROJECTION);
+	g3d_load_identity();
+	g3d_perspective(50.0, 1.33333, 0.5, 100.0);
+
+	start_time = time_msec;
+}
+
+static void update(void)
+{
+	static float prev_mx, prev_my;
+	static long prev_msec;
+	int mouse_dx, mouse_dy;
+	long msec = time_msec - start_time;
+	float dt = (msec - prev_msec) / 1000.0f;
+	prev_msec = msec;
+
+	mouse_dx = mouse_x - prev_mx;
+	mouse_dy = mouse_y - prev_my;
+	prev_mx = mouse_x;
+	prev_my = mouse_y;
+
+	if(mouse_bmask) {
+		hball.pos.x += mouse_dx * 0.05;
+		hball.pos.y -= mouse_dy * 0.05;
+	}
+
+	hball.rot = quat_rotate(hball.rot, dt * 2.0f, 0, 1, 0);
+
+	quat_to_mat(hball.xform, hball.rot);
+	hball.xform[12] = hball.pos.x;
+	hball.xform[13] = hball.pos.y;
+	hball.xform[14] = hball.pos.z;
+
+	update_hairball(&hball, dt);
+}
+
+static void draw(void)
+{
+	update();
+
+	memset(fb_pixels, 0, fb_width * fb_height * 2);
+
+	g3d_matrix_mode(G3D_MODELVIEW);
+	g3d_load_identity();
+	g3d_translate(0, 0, -8);
+
+	draw_hairball(&hball);
+
+	swap_buffers(fb_pixels);
+}
+
+static void update_hairball(struct hairball *hb, float dt)
+{
+	int i, j, spawn_count;
+	struct particle pdummy, *prev, *p;
+	static float spawn_acc;
+
+	/* update particles */
+	for(i=0; i<NSPAWNPOS; i++) {
+		pdummy.next = hb->plist[i];
+		prev = &pdummy;
+		while(prev && prev->next) {
+			p = prev->next;
+			if(--p->life <= 0) {
+				prev->next = p->next;
+				pfree(p);
+				prev = prev->next;
+				continue;
+			}
+
+			p->pos.x += p->vel.x * dt;
+			p->pos.y += p->vel.y * dt;
+			p->pos.z += p->vel.z * dt;
+			p->vel.y += GRAV * dt;
+			prev = p;
+		}
+
+		hb->plist[i] = pdummy.next;
+	}
+
+	/* spawn new particles */
+	spawn_acc += dt;
+	if(spawn_acc >= (1.0f / SPAWN_RATE)) {
+		for(i=0; i<NSPAWNPOS; i++) {
+			struct particle *p = palloc();
+			float *mat = hb->xform;
+			vec3_t pos = spawnpos[i];
+
+			p->pos.x = mat[0] * pos.x + mat[4] * pos.y + mat[8] * pos.z + mat[12];
+			p->pos.y = mat[1] * pos.x + mat[5] * pos.y + mat[9] * pos.z + mat[13];
+			p->pos.z = mat[2] * pos.x + mat[6] * pos.y + mat[10] * pos.z + mat[14];
+
+			p->vel = spawndir[i];
+			p->life = HAIR_LENGTH;
+			/* TODO color */
+
+			p->next = hb->plist[i];
+			hb->plist[i] = p;
+		}
+		spawn_acc -= 1.0f / SPAWN_RATE;
+	}
+}
+
+static void draw_hairball(struct hairball *hb)
+{
+	int i, j, col;
+	struct particle *p;
+	vec3_t prevpos;
+
+	g3d_begin(G3D_LINES);
+	for(i=0; i<NSPAWNPOS; i++) {
+		p = hb->plist[i];
+		prevpos.x = hb->xform[0] * spawnpos[i].x + hb->xform[4] * spawnpos[i].y + hb->xform[8] * spawnpos[i].z + hb->xform[12];
+		prevpos.y = hb->xform[1] * spawnpos[i].x + hb->xform[5] * spawnpos[i].y + hb->xform[9] * spawnpos[i].z + hb->xform[13];
+		prevpos.z = hb->xform[2] * spawnpos[i].x + hb->xform[6] * spawnpos[i].y + hb->xform[10] * spawnpos[i].z + hb->xform[14];
+
+		j = 0;
+		while(p) {
+			col = 255 - j++ * (HAIR_LENGTH - 1);
+			g3d_color3b(col, col, col);
+			g3d_vertex(prevpos.x, prevpos.y, prevpos.z);
+			g3d_vertex(p->pos.x, p->pos.y, p->pos.z);
+			prevpos = p->pos;
+			p = p->next;
+		}
+	}
+	g3d_end();
+}
+
+
+static struct particle *palloc(void)
+{
+	return malloc(sizeof(struct particle));
+}
+
+void pfree(struct particle *p)
+{
+	free(p);
+}
diff --git a/src/screen.c b/src/screen.c
index fa70413..b39778d 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -15,6 +15,7 @@ struct screen *thunder_screen(void);
 struct screen *metaballs_screen(void);
 struct screen *greets_screen(void);
 struct screen *infcubes_screen(void);
+struct screen *hairball_screen(void);
 
 #define NUM_SCR 32
 static struct screen *scr[NUM_SCR];
@@ -57,6 +58,9 @@ int scr_init(void)
 	if(!(scr[idx++] = infcubes_screen())) {
 		return -1;
 	}
+	if(!(scr[idx++] = hairball_screen())) {
+		return -1;
+	}
 	num_screens = idx;
 
 	assert(num_screens <= NUM_SCR);
diff --git a/src/vmath.h b/src/vmath.h
index 3cdbedf..463fea6 100644
--- a/src/vmath.h
+++ b/src/vmath.h
@@ -141,4 +141,22 @@ static INLINE void mat4_transpose(float *mat)
 	}
 }
 
+/* misc stuff */
+static vec3_t INLINE sphrand(float rad)
+{
+	vec3_t res;
+
+	float u = (float)rand() / RAND_MAX;
+	float v = (float)rand() / RAND_MAX;
+
+	float theta = 2.0f * M_PI * u;
+	float phi = acos(2.0f * v - 1.0f);
+
+	res.x = rad * cos(theta) * sin(phi);
+	res.y = rad * sin(theta) * sin(phi);
+	res.z = rad * cos(phi);
+
+	return res;
+}
+
 #endif	/* VMATH_H_ */
-- 
1.7.10.4