Update raymarch() to use a SceneResult

examples/test/shaders/test.frag

@@ -49,13 +49,13 @@ vec3 estimate_scene_normal(vec3 p) {
 vec3 raymarch(vec3 o, vec3 d, float start, float end) {
 	float t = start;
 	for (int i = 0; i < MAX_STEPS; i++) {
-		float dist = scene_f(o + d*t);
-		if (dist < EPSILON || t > end)
-			return vec3(t, i, 0.);
+		SceneResult sr = scene_f(o + d*t);
+		if (sr.d < EPSILON || t > end)
+			return vec3(t, sr.mat_idx, i);
 
-		t += dist;
+		t += sr.d;
 	}
-	return vec3(end, MAX_STEPS, 0.);
+	return vec3(end, -1., MAX_STEPS);
 }
 
 vec4 shade(vec3 p) {
@@ -77,7 +77,8 @@ void main() {
 
 	vec3 result = raymarch(eye, dir, NEAR_D, FAR_D);
 	float depth = result.x;
-	float iters = result.y;
+	float mat_idx = result.y;
+	float iters = result.z;
 	if (depth >= FAR_D) {
 		color = vec4(1.0, 0.5, 1.0, 1.0);
 		return;