# HG changeset patch
# User John Tsiombikas <nuclear@member.fsf.org>
# Date 1511700574 -7200
# Node ID f440ecffc45add55759cfa180562e7151be12dac
# Parent  03e8b9a5031d210f88c3884f6483dfcf90b47b13
trying to draw the orbit in the shader

diff -r 03e8b9a5031d -r f440ecffc45a mbrot.glsl
--- a/mbrot.glsl	Mon Nov 20 03:53:02 2017 +0200
+++ b/mbrot.glsl	Sun Nov 26 14:49:34 2017 +0200
@@ -1,5 +1,5 @@
 // vi:ft=glsl:
-#define ITER	96
+#define ITER	128
 
 uniform float view_scale;
 uniform vec2 view_center;
@@ -7,6 +7,7 @@
 
 float mbrot_dist_point(in vec2 c, in vec2 p)
 {
+	vec2 pixpos = c;
 	vec2 z = c;
 	float mindist_sq = 8192.0;
 
@@ -15,18 +16,59 @@
 		float y = (z.x * z.y + z.x * z.y) + c.y;
 
 		z = vec2(x, y);
-		vec2 dir = z - seed;
+		vec2 dir = z - p;
 		mindist_sq = min(mindist_sq, dot(dir, dir)); 
 	}
 
-	return sqrt(mindist_sq);
+	return mindist_sq;
+}
+
+float line_dist_sq(in vec2 a, in vec2 b, in vec2 p)
+{
+	vec2 dir = b - a;
+	vec2 pvec = p - a;
+	float t = dot(dir, pvec);
+
+	if(t < 0.0) return dot(pvec, pvec);
+	if(t > 1.0) return dot(p - b, p - b);
+
+	vec2 ppt = a + dir * t;
+	vec2 lpvec = p - ppt;
+	return dot(lpvec, lpvec);
+}
+
+float mbrot_orbit_dist(in vec2 c, in vec2 p)
+{
+	vec2 pixpos = c;
+	vec2 z = c;
+	float mindist_sq = 8192.0;
+
+	for(int i=0; i<ITER; i++) {
+		float x = (z.x * z.x - z.y * z.y) + c.x;
+		float y = (z.x * z.y + z.x * z.y) + c.y;
+		vec2 next = vec2(x, y);
+
+		float dist_sq = line_dist_sq(z, next, p);
+		mindist_sq = min(mindist_sq, dist_sq); 
+
+		z = next;
+	}
+
+	return mindist_sq;
 }
 
 void main()
 {
 	vec2 c = gl_TexCoord[0].xy;
-	float m = 1.0 - mbrot_dist_point(c, vec2(0.0, 0.0));
+	float pdist_sq;
+	float m = 1.0 - min(sqrt(mbrot_dist_point(c, seed)), 1.0);
 
+#ifdef PLOT_ORBIT
+	float orb_dist = sqrt(mbrot_orbit_dist(seed, c));
+	vec3 orbcol = vec3(0.001 / orb_dist, 0.0, 0.0);
+	gl_FragColor.rgb = vec3(m, m, m) / 2.0 + orbcol;
+#else
 	gl_FragColor.rgb = vec3(m, m, m);
+#endif
 	gl_FragColor.a = 1.0;
 }
diff -r 03e8b9a5031d -r f440ecffc45a src/main.c
--- a/src/main.c	Mon Nov 20 03:53:02 2017 +0200
+++ b/src/main.c	Sun Nov 26 14:49:34 2017 +0200
@@ -8,6 +8,17 @@
 #include <GL/glut.h>
 #include "sdr.h"
 
+enum {
+	SDR_LINE_DIST_BIT = 1,
+	SDR_PLOT_ORBIT_BIT = 2
+};
+const char *sdrdef[] = {
+	"#define LINE_DIST\n",
+	"#define PLOT_ORBIT\n"
+};
+#define NUM_SDR_BITS	(sizeof sdrdef / sizeof *sdrdef)
+#define NUM_SHADERS		(1 << NUM_SDR_BITS)
+
 int init(void);
 void cleanup(void);
 void disp(void);
@@ -21,11 +32,12 @@
 static int win_width = 1280, win_height = 800;
 static float win_aspect;
 static int mouse_x = 640, mouse_y = 400;
-static unsigned int prog_mbrot;
+static unsigned int prog_mbrot[NUM_SHADERS];
 
 static float view_center[2] = {0.7, 0.0};
 static float view_scale = 1.2;
 
+static unsigned int sdrflags;
 
 int main(int argc, char **argv)
 {
@@ -53,17 +65,57 @@
 
 int init(void)
 {
+	int i, j;
+	unsigned int vs = 0, ps[NUM_SHADERS] = {0};
+
 	glewInit();
 
-	if(!(prog_mbrot = create_program_load("vertex.glsl", "mbrot.glsl"))) {
+	if(!(vs = load_vertex_shader("vertex.glsl"))) {
 		return -1;
 	}
+
+	for(i=0; i<NUM_SHADERS; i++) {
+		clear_shader_header(GL_FRAGMENT_SHADER);
+		for(j=0; j<NUM_SDR_BITS; j++) {
+			if(i & (1 << j)) {
+				add_shader_header(GL_FRAGMENT_SHADER, sdrdef[j]);
+			}
+		}
+
+		if(!(ps[i] = load_pixel_shader("mbrot.glsl"))) {
+			goto err;
+		}
+
+		if(!(prog_mbrot[i] = create_program_link(vs, ps[i], 0))) {
+			goto err;
+		}
+	}
 	return 0;
+
+err:
+	for(i=0; i<NUM_SHADERS; i++) {
+		if(prog_mbrot[i]) {
+			free_program(prog_mbrot[i]);
+			prog_mbrot[i] = 0;
+		}
+		if(ps[i]) {
+			free_shader(ps[i]);
+		}
+	}
+	if(vs) {
+		free_shader(vs);
+	}
+	return -1;
 }
 
 void cleanup(void)
 {
-	free_program(prog_mbrot);
+	int i;
+
+	for(i=0; i<NUM_SHADERS; i++) {
+		free_program(prog_mbrot[i]);
+		prog_mbrot[i] = 0;
+	}
 }
 
 void pixel_to_complex(float *res, float px, float py)
@@ -83,10 +135,10 @@
 
 	pixel_to_complex(seed, mouse_x, mouse_y);
 
-	set_uniform_float2(prog_mbrot, "seed", seed[0], seed[1]);
-	set_uniform_float(prog_mbrot, "view_scale", view_scale);
-	set_uniform_float2(prog_mbrot, "view_center", view_center[0], view_center[1]);
-	glUseProgram(prog_mbrot);
+	set_uniform_float2(prog_mbrot[sdrflags], "seed", seed[0], seed[1]);
+	set_uniform_float(prog_mbrot[sdrflags], "view_scale", view_scale);
+	set_uniform_float2(prog_mbrot[sdrflags], "view_center", view_center[0], view_center[1]);
+	glUseProgram(prog_mbrot[sdrflags]);
 
 	glBegin(GL_QUADS);
 	for(i=0; i<4; i++) {
@@ -131,6 +183,16 @@
 		}
 		break;
 
+	case ' ':
+		sdrflags ^= SDR_LINE_DIST_BIT;
+		glutPostRedisplay();
+		break;
+
+	case 'o':
+		sdrflags ^= SDR_PLOT_ORBIT_BIT;
+		glutPostRedisplay();
+		break;
+
 	case '`':
 		screenshot();
 		break;