nuclear@2: #include "brdf.h"
nuclear@2: #include "erebus_impl.h"
nuclear@2: 
nuclear@2: // ---- class Reflectance ----
nuclear@2: Reflectance::Reflectance()
nuclear@2: {
nuclear@2: }
nuclear@2: 
nuclear@2: float Reflectance::sample(const Vector3 &norm, const Vector3 &outdir, Vector3 *indir) const
nuclear@2: {
nuclear@2: 	*indir = sample_dir(norm, outdir);
nuclear@2: 	return eval(norm, outdir, *indir);
nuclear@2: }
nuclear@2: 
nuclear@21: // --- class CompositeRefl ----
nuclear@21: CompositeRefl::CompositeRefl()
nuclear@21: {
nuclear@21: 	valid_checked = false;
nuclear@21: }
nuclear@21: 
nuclear@21: int CompositeRefl::pick_brdf(const Vector3 &norm, const Vector3 &outdir) const
nuclear@21: {
nuclear@21: 	if(sub_brdf.empty()) {
nuclear@21: 		return -1;
nuclear@21: 	}
nuclear@21: 
nuclear@21: 	int brdf_count = (int)sub_brdf.size();
nuclear@21: 	if(brdf_count == 1) {
nuclear@21: 		return 0;
nuclear@21: 	}
nuclear@21: 
nuclear@21: 	// construct CDF from sub-brdf probabilities
nuclear@21: 	float *cdf = (float*)alloca(brdf_count * sizeof *cdf);
nuclear@21: 	for(int i=0; i<brdf_count; i++) {
nuclear@21: 		const SubRefl &sub = sub_brdf[i];
nuclear@21: 		float w = sub.weight_func ? sub.weight_func(norm, outdir) : sub.weight;
nuclear@21: 		cdf[i] = i > 0 ? cdf[i - 1] + w : w;
nuclear@21: 	}
nuclear@21: 
nuclear@21: 	float rval = randf(0.0, cdf[brdf_count - 1]);
nuclear@21: 	for(int i=0; i<brdf_count - 1; i++) {
nuclear@21: 		if(rval <= cdf[i]) return i;
nuclear@21: 	}
nuclear@21: 	return brdf_count - 1;
nuclear@21: }
nuclear@21: 
nuclear@21: void CompositeRefl::add_brdf(Reflectance *brdf, float weight)
nuclear@21: {
nuclear@21: 	SubRefl sub;
nuclear@21: 	sub.brdf = brdf;
nuclear@21: 	sub.weight = weight;
nuclear@21: 	sub.weight_func = 0;
nuclear@21: 	sub_brdf.push_back(sub);
nuclear@21: 
nuclear@21: 	valid_checked = false;
nuclear@21: }
nuclear@21: 
nuclear@21: void CompositeRefl::add_brdf(Reflectance *brdf, CompReflWeightFunc weight_func)
nuclear@21: {
nuclear@21: 	SubRefl sub;
nuclear@21: 	sub.brdf = brdf;
nuclear@21: 	sub.weight = 0.0;
nuclear@21: 	sub.weight_func = weight_func;
nuclear@21: 	sub_brdf.push_back(sub);
nuclear@21: 
nuclear@21: 	valid_checked = false;
nuclear@21: }
nuclear@21: 
nuclear@21: bool CompositeRefl::check_valid() const
nuclear@21: {
nuclear@21: 	float sum = 0.0;
nuclear@21: 	for(size_t i=0; i<sub_brdf.size(); i++) {
nuclear@21: 		if(!sub_brdf[i].weight_func) {
nuclear@21: 			sum += sub_brdf[i].weight;
nuclear@21: 		}
nuclear@21: 	}
nuclear@21: 	return sum < 1.0001;
nuclear@21: }
nuclear@21: 
nuclear@21: static bool warned_composite_usage;
nuclear@21: static const char *composite_usage_warnstr =
nuclear@21: 	"warning: don't call CompositeRefl's sample_dir and eval separately\n"
nuclear@21: 	"         it'll pick different brdfs each time! use sample instead\n";
nuclear@21: 
nuclear@21: Vector3 CompositeRefl::sample_dir(const Vector3 &norm, const Vector3 &outdir) const
nuclear@21: {
nuclear@21: 	if(!warned_composite_usage) {
nuclear@21: 		fputs(composite_usage_warnstr, stderr);
nuclear@21: 		warned_composite_usage = true;
nuclear@21: 	}
nuclear@21: 	int bidx = pick_brdf(norm, outdir);
nuclear@21: 	return sub_brdf[bidx].brdf->sample_dir(norm, outdir);
nuclear@21: }
nuclear@21: 
nuclear@21: float CompositeRefl::sample(const Vector3 &norm, const Vector3 &outdir, Vector3 *indir) const
nuclear@21: {
nuclear@21: 	int bidx = pick_brdf(norm, outdir);
nuclear@21: 	return sub_brdf[bidx].brdf->sample(norm, outdir, indir);
nuclear@21: }
nuclear@21: 
nuclear@21: float CompositeRefl::eval(const Vector3 &norm, const Vector3 &outdir, const Vector3 &indir) const
nuclear@21: {
nuclear@21: 	if(!warned_composite_usage) {
nuclear@21: 		fputs(composite_usage_warnstr, stderr);
nuclear@21: 		warned_composite_usage = true;
nuclear@21: 	}
nuclear@21: 	int bidx = pick_brdf(norm, outdir);
nuclear@21: 	return sub_brdf[bidx].brdf->eval(norm, outdir, indir);
nuclear@21: }
nuclear@21: 
nuclear@2: // --- class LambertRefl ---
nuclear@2: Vector3 LambertRefl::sample_dir(const Vector3 &norm, const Vector3 &outdir) const
nuclear@2: {
nuclear@2: 	Vector3 dir = Vector3{randf(-1, 1), randf(-1, 1), randf(-1, 1)}.normalized();
nuclear@2: 	return dot_product(dir, norm) < 0.0 ? -dir : dir;
nuclear@2: }
nuclear@2: 
nuclear@2: float LambertRefl::eval(const Vector3 &norm, const Vector3 &outdir, const Vector3 &indir) const
nuclear@2: {
nuclear@2: 	return dot_product(norm, outdir);
nuclear@2: }
nuclear@21: 
nuclear@21: // --- class MirrorRefl ---
nuclear@21: Vector3 MirrorRefl::sample_dir(const Vector3 &norm, const Vector3 &outdir) const
nuclear@21: {
nuclear@21: 	return outdir.reflection(norm);
nuclear@21: }
nuclear@21: 
nuclear@21: float MirrorRefl::eval(const Vector3 &norm, const Vector3 &outdir, const Vector3 &indir) const
nuclear@21: {
nuclear@21: 	return 1.0f;
nuclear@21: }