# HG changeset patch
# User John Tsiombikas <nuclear@member.fsf.org>
# Date 1401249989 -10800
# Node ID e49f4d7ad04c3f38ec4a96aee13e8f67f785545b
# Parent  ea95b62dbc87499e606409689364f75ee6bf7b7c
started adding BRDFs

diff -r ea95b62dbc87 -r e49f4d7ad04c liberebus/src/brdf.cc
--- a/liberebus/src/brdf.cc	Tue May 27 07:49:09 2014 +0300
+++ b/liberebus/src/brdf.cc	Wed May 28 07:06:29 2014 +0300
@@ -12,6 +12,102 @@
 	return eval(norm, outdir, *indir);
 }
 
+// --- class CompositeRefl ----
+CompositeRefl::CompositeRefl()
+{
+	valid_checked = false;
+}
+
+int CompositeRefl::pick_brdf(const Vector3 &norm, const Vector3 &outdir) const
+{
+	if(sub_brdf.empty()) {
+		return -1;
+	}
+
+	int brdf_count = (int)sub_brdf.size();
+	if(brdf_count == 1) {
+		return 0;
+	}
+
+	// construct CDF from sub-brdf probabilities
+	float *cdf = (float*)alloca(brdf_count * sizeof *cdf);
+	for(int i=0; i<brdf_count; i++) {
+		const SubRefl &sub = sub_brdf[i];
+		float w = sub.weight_func ? sub.weight_func(norm, outdir) : sub.weight;
+		cdf[i] = i > 0 ? cdf[i - 1] + w : w;
+	}
+
+	float rval = randf(0.0, cdf[brdf_count - 1]);
+	for(int i=0; i<brdf_count - 1; i++) {
+		if(rval <= cdf[i]) return i;
+	}
+	return brdf_count - 1;
+}
+
+void CompositeRefl::add_brdf(Reflectance *brdf, float weight)
+{
+	SubRefl sub;
+	sub.brdf = brdf;
+	sub.weight = weight;
+	sub.weight_func = 0;
+	sub_brdf.push_back(sub);
+
+	valid_checked = false;
+}
+
+void CompositeRefl::add_brdf(Reflectance *brdf, CompReflWeightFunc weight_func)
+{
+	SubRefl sub;
+	sub.brdf = brdf;
+	sub.weight = 0.0;
+	sub.weight_func = weight_func;
+	sub_brdf.push_back(sub);
+
+	valid_checked = false;
+}
+
+bool CompositeRefl::check_valid() const
+{
+	float sum = 0.0;
+	for(size_t i=0; i<sub_brdf.size(); i++) {
+		if(!sub_brdf[i].weight_func) {
+			sum += sub_brdf[i].weight;
+		}
+	}
+	return sum < 1.0001;
+}
+
+static bool warned_composite_usage;
+static const char *composite_usage_warnstr =
+	"warning: don't call CompositeRefl's sample_dir and eval separately\n"
+	"         it'll pick different brdfs each time! use sample instead\n";
+
+Vector3 CompositeRefl::sample_dir(const Vector3 &norm, const Vector3 &outdir) const
+{
+	if(!warned_composite_usage) {
+		fputs(composite_usage_warnstr, stderr);
+		warned_composite_usage = true;
+	}
+	int bidx = pick_brdf(norm, outdir);
+	return sub_brdf[bidx].brdf->sample_dir(norm, outdir);
+}
+
+float CompositeRefl::sample(const Vector3 &norm, const Vector3 &outdir, Vector3 *indir) const
+{
+	int bidx = pick_brdf(norm, outdir);
+	return sub_brdf[bidx].brdf->sample(norm, outdir, indir);
+}
+
+float CompositeRefl::eval(const Vector3 &norm, const Vector3 &outdir, const Vector3 &indir) const
+{
+	if(!warned_composite_usage) {
+		fputs(composite_usage_warnstr, stderr);
+		warned_composite_usage = true;
+	}
+	int bidx = pick_brdf(norm, outdir);
+	return sub_brdf[bidx].brdf->eval(norm, outdir, indir);
+}
+
 // --- class LambertRefl ---
 Vector3 LambertRefl::sample_dir(const Vector3 &norm, const Vector3 &outdir) const
 {
@@ -23,3 +119,14 @@
 {
 	return dot_product(norm, outdir);
 }
+
+// --- class MirrorRefl ---
+Vector3 MirrorRefl::sample_dir(const Vector3 &norm, const Vector3 &outdir) const
+{
+	return outdir.reflection(norm);
+}
+
+float MirrorRefl::eval(const Vector3 &norm, const Vector3 &outdir, const Vector3 &indir) const
+{
+	return 1.0f;
+}
diff -r ea95b62dbc87 -r e49f4d7ad04c liberebus/src/brdf.h
--- a/liberebus/src/brdf.h	Tue May 27 07:49:09 2014 +0300
+++ b/liberebus/src/brdf.h	Wed May 28 07:06:29 2014 +0300
@@ -1,6 +1,7 @@
 #ifndef BRDF_H_
 #define BRDF_H_
 
+#include <vector>
 #include "texture.h"
 
 class Reflectance {
@@ -13,10 +14,43 @@
 	virtual float eval(const Vector3 &norm, const Vector3 &outdir, const Vector3 &indir) const = 0;
 };
 
+typedef float (*CompReflWeightFunc)(const Vector3 &norm, const Vector3 &outdir);
+
+class CompositeRefl : public Reflectance {
+private:
+	struct SubRefl {
+		Reflectance *brdf;
+		float weight;
+		CompReflWeightFunc weight_func;	// if null, use static weight above
+	};
+	std::vector<SubRefl> sub_brdf;
+	mutable bool valid_checked;
+
+	int pick_brdf(const Vector3 &norm, const Vector3 &outdir) const;
+
+public:
+	CompositeRefl();
+
+	virtual void add_brdf(Reflectance *brdf, float weight);
+	virtual void add_brdf(Reflectance *brdf, CompReflWeightFunc weight_func);
+
+	bool check_valid() const;
+
+	Vector3 sample_dir(const Vector3 &norm, const Vector3 &outdir) const override;
+	float sample(const Vector3 &norm, const Vector3 &outdir, Vector3 *indir) const override;
+	float eval(const Vector3 &norm, const Vector3 &outdir, const Vector3 &indir) const override;
+};
+
 class LambertRefl : public Reflectance {
 public:
 	Vector3 sample_dir(const Vector3 &norm, const Vector3 &outdir) const override;
 	float eval(const Vector3 &norm, const Vector3 &outdir, const Vector3 &indir) const override;
 };
 
+class MirrorRefl : public Reflectance {
+public:
+	Vector3 sample_dir(const Vector3 &norm, const Vector3 &outdir) const override;
+	float eval(const Vector3 &norm, const Vector3 &outdir, const Vector3 &indir) const override;
+};
+
 #endif	// BRDF_H_
diff -r ea95b62dbc87 -r e49f4d7ad04c src/main.cc
--- a/src/main.cc	Tue May 27 07:49:09 2014 +0300
+++ b/src/main.cc	Wed May 28 07:06:29 2014 +0300
@@ -75,10 +75,12 @@
 		}
 	}
 
-	printf("begin rendering\n");
-	render_pending = true;
-	glutIdleFunc(idle);
-	erb_begin_frame(erb, 0);
+	if(!sfiles.empty()) {
+		printf("begin rendering\n");
+		render_pending = true;
+		glutIdleFunc(idle);
+		erb_begin_frame(erb, 0);
+	}
 
 	glEnable(GL_TEXTURE_2D);
 	return true;