# HG changeset patch
# User John Tsiombikas <nuclear@member.fsf.org>
# Date 1334355223 -10800
# Node ID 63bc059778d0c80adeee8b61e3536ef6ce3dc2af
# Parent  c27ce79632dbbdd8ede55c13b8f9549ed2f54797
fixed ray marching

diff -r c27ce79632db -r 63bc059778d0 sdr/volray.p.glsl
--- a/sdr/volray.p.glsl	Sat Apr 14 00:54:11 2012 +0300
+++ b/sdr/volray.p.glsl	Sat Apr 14 01:13:43 2012 +0300
@@ -24,22 +24,40 @@
 vec3 shade(Ray ray, vec3 pos, vec3 norm);
 Ray get_primary_ray();
 ISect intersect_aabb(Ray ray, AABBox aabb);
+ISect intersect_sphere(Ray ray, float rad);
+
+//#define USE_AABB
 
 void main()
 {
-	const AABBox aabb = AABBox(vec3(-1.0, -1.0, -1.0), vec3(1.0, 1.0, 1.0));
 	Ray ray = get_primary_ray();
 
 	vec3 color = vec3(0.0, 0.0, 0.0);
 
+#ifdef USE_AABB
+	const AABBox aabb = AABBox(vec3(-1.0, -1.0, -1.0), vec3(1.0, 1.0, 1.0));
 	ISect res = intersect_aabb(ray, aabb);
 	if(res.hit) {
-		color = ray_march(ray, res.t0, res.t1);
+		color += ray_march(ray, res.t0, res.t1);
 	}
+#else
+	ISect res = intersect_sphere(ray, 1.5);
+	if(res.hit) {
+		color += ray_march(ray, res.t0, res.t1);
+	}
+#endif
 
 	gl_FragColor = vec4(color, 1.0);
 }
 
+vec3 sky(Ray ray)
+{
+	vec3 c0 = vec3(0.2, 0.5, 0.8);
+	vec3 c1 = vec3(0.8, 0.5, 0.2);
+	float t = smoothstep(-0.2, 0.2, ray.dir.z);
+	return mix(c0, c1, t);
+}
+
 float eval(vec3 pos, out vec3 grad)
 {
 	vec3 tc = pos * 0.5 + 0.5;
@@ -55,7 +73,6 @@
 	return texture1D(xfer_tex, texel.a).x;
 }
 
-#define OFFS	0.01
 vec3 ray_march(Ray ray, float t0, float t1)
 {
 	float energy = 1.0;
@@ -70,12 +87,15 @@
 		vec3 norm;
 		float val = eval(pos, norm);
 
-		col += shade(ray, pos, normalize(norm)) * val * energy;
-		energy -= val;
+		float energy_drop = exp(val * -ray_step);	// * scatter_coeff ?
+		energy *= energy_drop;
+
+		vec3 irrad = shade(ray, pos, normalize(norm));
+
+		col += (1.0 - energy_drop) * energy * irrad;
 		if(energy < 0.001) {
 			break;
 		}
-		pos += ray.dir * ray_step;
 	}
 
 	return col;
@@ -83,17 +103,17 @@
 
 vec3 shade(Ray ray, vec3 pos, vec3 norm)
 {
-	vec3 ldir = -pos;//normalize(vec3(10.0, 10.0, -10.0) - pos);
-	vec3 vdir = -ray.dir;
-	vec3 hdir = normalize(ldir + vdir);
+	vec3 ldir = -normalize(ray.dir);
+	vec3 vdir = ldir;
+	vec3 hdir = ldir;//normalize(ldir + vdir);
 
-	float ndotl = dot(ldir, norm);
-	float ndoth = dot(hdir, norm);
+	float ndotl = abs(dot(ldir, norm));
+	float ndoth = abs(dot(hdir, norm));
 
 	vec3 dcol = vec3(0.9, 0.9, 0.9) * max(ndotl, 0.0);
 	vec3 scol = vec3(0.5, 0.5, 0.5) * pow(max(ndoth, 0.0), 50.0);
 
-	return vec3(0.01, 0.01, 0.01) + dcol + scol;
+	return dcol + scol;
 }
 
 Ray get_primary_ray()
@@ -153,3 +173,31 @@
 	return res;
 }
 
+
+ISect intersect_sphere(Ray ray, float rad)
+{
+	ISect res;
+	res.hit = false;
+	res.t0 = res.t1 = 0.0;
+
+	float a = dot(ray.dir, ray.dir);
+	float b = 2.0 * dot(ray.dir, ray.origin);
+	float c = dot(ray.origin, ray.origin) - rad * rad;
+	float d = b * b - 4.0 * a * c;
+
+	if(d < 0.0) {
+		return res;
+	}
+
+	float sqrt_d = sqrt(d);
+	float t0 = (-b + sqrt_d) / (2.0 * a);
+	float t1 = (-b - sqrt_d) / (2.0 * a);
+
+	res.t0 = min(t0, t1);
+	res.t1 = max(t0, t1);
+	res.hit = true;
+
+	/*res.pos = ray.origin + ray.dir * res.t0;
+	res.normal = normalize(res.pos);*/
+	return res;
+}