* Adaptive QMC AO feature - "Adapt from speed vectors"

This is a new feature that can make using AO a lot more attractive when rendering 
animations with vector blur. It uses the speed vector info calculated in the 'Vec' 
speed vector pass, in order to reduce AO samples where pixels are moving more 
quickly. There's not much point calculating all those AO samples when the result is 
going to be smeared anyway, so you can save a bit of render time by doing 
a more noisy render in those areas.


You can use this with a new slider in the Adaptive QMC settings 'Adapt Vec'. The 
higher the value, the more aggressively it will reduce samples. 0.0 means no 
reduction, and 1.0 reduces one sample per pixel of average displacement for that 
pixel. 0.25 or so generally gives decent results, but it depends on how fast things 
are moving.

Here's a demo (compare the final blurred result, and render times):
http://mke3.net/blender/devel/raytracing/adapt_speed_off2.jpg
http://mke3.net/blender/devel/raytracing/adapt_speed_on2.jpg

And a less contrived example, a short clip from macouno's 'petunia' bconf animation:
http://mke3.net/blender/devel/raytracing/petunia-adaptvec-noblur-h264.mov
http://mke3.net/blender/devel/raytracing/petunia-adaptvec-blur-h264.mov

1 files changed, 42 insertions, 3 deletions

diff --git a/source/blender/render/intern/source/rayshade.c b/source/blender/render/intern/source/rayshade.c
index 560d2151e42..3a859b083ed 100644
--- a/source/blender/render/intern/source/rayshade.c
+++ b/source/blender/render/intern/source/rayshade.c
@@ -806,6 +806,23 @@ static void QMC_sampleHemi(float *vec, QMCSampler *qsa, int thread, int num)
 	vec[2] = 1.f - s[1]*s[1];
 }
 
+/* cosine weighted hemisphere sampling */
+static void QMC_sampleHemiCosine(float *vec, QMCSampler *qsa, int thread, int num)
+{
+	double s[2];
+	float phi, sqr;
+	
+	QMC_getSample(s, qsa, thread, num);
+	
+	phi = s[0]*2.f*M_PI;	
+	sqr = s[1]*sqrt(2-s[1]*s[1]);
+
+	vec[0] = cos(phi)*sqr;
+	vec[1] = sin(phi)*sqr;
+	vec[2] = 1.f - s[1]*s[1];
+
+}
+
 /* called from convertBlenderScene.c */
 /* samples don't change per pixel, so build the samples in advance for efficiency */
 void init_lamp_hammersley(LampRen *lar)
@@ -861,6 +878,20 @@ static int adaptive_sample_contrast_val(int samples, float prev, float val, floa
 		return 0;
 }
 
+static float get_avg_speed(ShadeInput *shi)
+{
+	float pre_x, pre_y, post_x, post_y, speedavg;
+	
+	pre_x = (shi->winspeed[0] == PASS_VECTOR_MAX)?0.0:shi->winspeed[0];
+	pre_y = (shi->winspeed[1] == PASS_VECTOR_MAX)?0.0:shi->winspeed[1];
+	post_x = (shi->winspeed[2] == PASS_VECTOR_MAX)?0.0:shi->winspeed[2];
+	post_y = (shi->winspeed[3] == PASS_VECTOR_MAX)?0.0:shi->winspeed[3];
+	
+	speedavg = (sqrt(pre_x*pre_x + pre_y*pre_y) + sqrt(post_x*post_x + post_y*post_y)) / 2.0;
+	
+	return speedavg;
+}
+
 /* ***************** main calls ************** */
 
 
@@ -1407,6 +1438,7 @@ void ray_ao_qmc(ShadeInput *shi, float *shadfac)
 	float maxdist = R.wrld.aodist;
 	float fac=0.0f, prev=0.0f;
 	float adapt_thresh = G.scene->world->ao_adapt_thresh;
+	float adapt_speed_fac = G.scene->world->ao_adapt_speed_fac;
 	float bias = G.scene->world->aobias;
 	
 	int samples=0;
@@ -1447,9 +1479,16 @@ void ray_ao_qmc(ShadeInput *shi, float *shadfac)
 	VecOrthoBasisf(nrm, up, side);
 	
 	/* sampling init */
-	if (R.wrld.ao_samp_method==WO_AOSAMP_HALTON) 
+	if (R.wrld.ao_samp_method==WO_AOSAMP_HALTON) {
+		float speedfac;
+		
+		speedfac = get_avg_speed(shi) * adapt_speed_fac;
+		CLAMP(speedfac, 1.0, 1000.0);
+		max_samples /= speedfac;
+		if (max_samples < 5) max_samples = 5;
+		
 		qsa = QMC_initSampler(SAMP_TYPE_HALTON, max_samples);
-	else if (R.wrld.ao_samp_method==WO_AOSAMP_HAMMERSLEY)
+	} else if (R.wrld.ao_samp_method==WO_AOSAMP_HAMMERSLEY)
 		qsa = R.qsa;
 
 	QMC_initPixel(qsa, shi->thread);
@@ -1458,7 +1497,7 @@ void ray_ao_qmc(ShadeInput *shi, float *shadfac)
 
 		/* sampling, returns quasi-random vector in unit hemisphere */
 		QMC_sampleHemi(samp3d, qsa, shi->thread, samples);
-		
+
 		dir[0] = (samp3d[0]*up[0] + samp3d[1]*side[0] + samp3d[2]*nrm[0]);
 		dir[1] = (samp3d[0]*up[1] + samp3d[1]*side[1] + samp3d[2]*nrm[1]);
 		dir[2] = (samp3d[0]*up[2] + samp3d[1]*side[2] + samp3d[2]*nrm[2]);