Cycles: option to make background visible through glass transparent.

This can be enabled in the Film panel, with an option to control the
transmisison roughness below which glass becomes transparent.

Differential Revision: https://developer.blender.org/D2904

6 files changed, 33 insertions, 20 deletions

diff --git a/intern/cycles/kernel/closure/bsdf.h b/intern/cycles/kernel/closure/bsdf.h
index e4573024e85..6f0bdb3fa38 100644
--- a/intern/cycles/kernel/closure/bsdf.h
+++ b/intern/cycles/kernel/closure/bsdf.h
@@ -38,7 +38,7 @@ CCL_NAMESPACE_BEGIN
 
 /* Returns the square of the roughness of the closure if it has roughness,
  * 0 for singular closures and 1 otherwise. */
-ccl_device_inline float bsdf_get_roughness_sqr(const ShaderClosure *sc)
+ccl_device_inline float bsdf_get_roughness_squared(const ShaderClosure *sc)
 {
 	if(CLOSURE_IS_BSDF_SINGULAR(sc->type)) {
 		return 0.0f;
@@ -173,6 +173,17 @@ ccl_device_forceinline int bsdf_sample(KernelGlobals *kg,
 			break;
 	}
 
+	/* Test if BSDF sample should be treated as transparent for background. */
+	if(label & LABEL_TRANSMIT) {
+		float threshold_squared = kernel_data.background.transparent_roughness_squared_threshold;
+
+		if(threshold_squared >= 0.0f) {
+			if(bsdf_get_roughness_squared(sc) <= threshold_squared) {
+				label |= LABEL_TRANSMIT_TRANSPARENT;
+			}
+		}
+	}
+
 	return label;
 }
 
diff --git a/intern/cycles/kernel/kernel_accumulate.h b/intern/cycles/kernel/kernel_accumulate.h
index 7c1b2a015e1..c0f281cae97 100644
--- a/intern/cycles/kernel/kernel_accumulate.h
+++ b/intern/cycles/kernel/kernel_accumulate.h
@@ -455,7 +455,7 @@ ccl_device_inline void path_radiance_accum_background(
 
 #ifdef __PASSES__
 	if(L->use_light_pass) {
-		if(state->bounce == 0)
+		if(state->flag & PATH_RAY_TRANSPARENT_BACKGROUND)
 			L->background += throughput*value;
 		else if(state->bounce == 1)
 			L->direct_emission += throughput*value;
diff --git a/intern/cycles/kernel/kernel_passes.h b/intern/cycles/kernel/kernel_passes.h
index 29451b6b8b6..1933d695f92 100644
--- a/intern/cycles/kernel/kernel_passes.h
+++ b/intern/cycles/kernel/kernel_passes.h
@@ -140,7 +140,7 @@ ccl_device_inline void kernel_update_denoising_features(KernelGlobals *kg,
 		/* All closures contribute to the normal feature, but only diffuse-like ones to the albedo. */
 		normal += sc->N * sc->sample_weight;
 		sum_weight += sc->sample_weight;
-		if(bsdf_get_roughness_sqr(sc) > sqr(0.075f)) {
+		if(bsdf_get_roughness_squared(sc) > sqr(0.075f)) {
 			albedo += sc->weight;
 			sum_nonspecular_weight += sc->sample_weight;
 		}
diff --git a/intern/cycles/kernel/kernel_path.h b/intern/cycles/kernel/kernel_path.h
index c2421c1ec18..1e98bca66ad 100644
--- a/intern/cycles/kernel/kernel_path.h
+++ b/intern/cycles/kernel/kernel_path.h
@@ -136,7 +136,7 @@ ccl_device_forceinline void kernel_path_background(
 	PathRadiance *L)
 {
 	/* eval background shader if nothing hit */
-	if(kernel_data.background.transparent && (state->flag & PATH_RAY_CAMERA)) {
+	if(kernel_data.background.transparent && (state->flag & PATH_RAY_TRANSPARENT_BACKGROUND)) {
 		L->transparent += average(throughput);
 
 #ifdef __PASSES__
@@ -280,7 +280,7 @@ ccl_device_forceinline bool kernel_path_shader_apply(
 {
 #ifdef __SHADOW_TRICKS__
 	if((sd->object_flag & SD_OBJECT_SHADOW_CATCHER)) {
-		if(state->flag & PATH_RAY_CAMERA) {
+		if(state->flag & PATH_RAY_TRANSPARENT_BACKGROUND) {
 			state->flag |= (PATH_RAY_SHADOW_CATCHER |
 						   PATH_RAY_STORE_SHADOW_INFO);
 
@@ -302,7 +302,7 @@ ccl_device_forceinline bool kernel_path_shader_apply(
 #ifdef __HOLDOUT__
 	if(((sd->flag & SD_HOLDOUT) ||
 		(sd->object_flag & SD_OBJECT_HOLDOUT_MASK)) &&
-	   (state->flag & PATH_RAY_CAMERA))
+	   (state->flag & PATH_RAY_TRANSPARENT_BACKGROUND))
 	{
 		if(kernel_data.background.transparent) {
 			float3 holdout_weight;
diff --git a/intern/cycles/kernel/kernel_path_state.h b/intern/cycles/kernel/kernel_path_state.h
index eccee54c0e3..505eed117e0 100644
--- a/intern/cycles/kernel/kernel_path_state.h
+++ b/intern/cycles/kernel/kernel_path_state.h
@@ -23,7 +23,7 @@ ccl_device_inline void path_state_init(KernelGlobals *kg,
                                        int sample,
                                        ccl_addr_space Ray *ray)
 {
-	state->flag = PATH_RAY_CAMERA|PATH_RAY_MIS_SKIP;
+	state->flag = PATH_RAY_CAMERA|PATH_RAY_MIS_SKIP|PATH_RAY_TRANSPARENT_BACKGROUND;
 
 	state->rng_hash = rng_hash;
 	state->rng_offset = PRNG_BASE_NUM;
@@ -86,12 +86,13 @@ ccl_device_inline void path_state_next(KernelGlobals *kg, ccl_addr_space PathSta
 	}
 
 	state->bounce++;
+	state->flag &= ~(PATH_RAY_ALL_VISIBILITY|PATH_RAY_MIS_SKIP);
 
 #ifdef __VOLUME__
 	if(label & LABEL_VOLUME_SCATTER) {
 		/* volume scatter */
 		state->flag |= PATH_RAY_VOLUME_SCATTER;
-		state->flag &= ~(PATH_RAY_REFLECT|PATH_RAY_TRANSMIT|PATH_RAY_CAMERA|PATH_RAY_TRANSPARENT|PATH_RAY_DIFFUSE|PATH_RAY_GLOSSY|PATH_RAY_SINGULAR|PATH_RAY_MIS_SKIP);
+		state->flag &= ~PATH_RAY_TRANSPARENT_BACKGROUND;
 
 		state->volume_bounce++;
 	}
@@ -101,7 +102,7 @@ ccl_device_inline void path_state_next(KernelGlobals *kg, ccl_addr_space PathSta
 		/* surface reflection/transmission */
 		if(label & LABEL_REFLECT) {
 			state->flag |= PATH_RAY_REFLECT;
-			state->flag &= ~(PATH_RAY_TRANSMIT|PATH_RAY_VOLUME_SCATTER|PATH_RAY_CAMERA|PATH_RAY_TRANSPARENT);
+			state->flag &= ~PATH_RAY_TRANSPARENT_BACKGROUND;
 
 			if(label & LABEL_DIFFUSE)
 				state->diffuse_bounce++;
@@ -112,7 +113,10 @@ ccl_device_inline void path_state_next(KernelGlobals *kg, ccl_addr_space PathSta
 			kernel_assert(label & LABEL_TRANSMIT);
 
 			state->flag |= PATH_RAY_TRANSMIT;
-			state->flag &= ~(PATH_RAY_REFLECT|PATH_RAY_VOLUME_SCATTER|PATH_RAY_CAMERA|PATH_RAY_TRANSPARENT);
+
+			if(!(label & LABEL_TRANSMIT_TRANSPARENT)) {
+				state->flag &= ~PATH_RAY_TRANSPARENT_BACKGROUND;
+			}
 
 			state->transmission_bounce++;
 		}
@@ -120,17 +124,13 @@ ccl_device_inline void path_state_next(KernelGlobals *kg, ccl_addr_space PathSta
 		/* diffuse/glossy/singular */
 		if(label & LABEL_DIFFUSE) {
 			state->flag |= PATH_RAY_DIFFUSE|PATH_RAY_DIFFUSE_ANCESTOR;
-			state->flag &= ~(PATH_RAY_GLOSSY|PATH_RAY_SINGULAR|PATH_RAY_MIS_SKIP);
 		}
 		else if(label & LABEL_GLOSSY) {
 			state->flag |= PATH_RAY_GLOSSY;
-			state->flag &= ~(PATH_RAY_DIFFUSE|PATH_RAY_SINGULAR|PATH_RAY_MIS_SKIP);
 		}
 		else {
 			kernel_assert(label & LABEL_SINGULAR);
-
 			state->flag |= PATH_RAY_GLOSSY|PATH_RAY_SINGULAR|PATH_RAY_MIS_SKIP;
-			state->flag &= ~PATH_RAY_DIFFUSE;
 		}
 	}
 
diff --git a/intern/cycles/kernel/kernel_types.h b/intern/cycles/kernel/kernel_types.h
index b052d668b7d..4f655784044 100644
--- a/intern/cycles/kernel/kernel_types.h
+++ b/intern/cycles/kernel/kernel_types.h
@@ -346,11 +346,12 @@ enum PathRayFlag {
 
 	PATH_RAY_ALL_VISIBILITY = ((1 << 14)-1),
 
-	PATH_RAY_MIS_SKIP            = (1 << 15),
-	PATH_RAY_DIFFUSE_ANCESTOR    = (1 << 16),
-	PATH_RAY_SINGLE_PASS_DONE    = (1 << 17),
-	PATH_RAY_SHADOW_CATCHER      = (1 << 18),
-	PATH_RAY_STORE_SHADOW_INFO   = (1 << 19),
+	PATH_RAY_MIS_SKIP               = (1 << 15),
+	PATH_RAY_DIFFUSE_ANCESTOR       = (1 << 16),
+	PATH_RAY_SINGLE_PASS_DONE       = (1 << 17),
+	PATH_RAY_SHADOW_CATCHER         = (1 << 18),
+	PATH_RAY_STORE_SHADOW_INFO      = (1 << 19),
+	PATH_RAY_TRANSPARENT_BACKGROUND = (1 << 20),
 };
 
 /* Closure Label */
@@ -364,6 +365,7 @@ typedef enum ClosureLabel {
 	LABEL_SINGULAR = 16,
 	LABEL_TRANSPARENT = 32,
 	LABEL_VOLUME_SCATTER = 64,
+	LABEL_TRANSMIT_TRANSPARENT = 128,
 } ClosureLabel;
 
 /* Render Passes */
@@ -1259,7 +1261,7 @@ typedef struct KernelBackground {
 	int surface_shader;
 	int volume_shader;
 	int transparent;
-	int pad;
+	float transparent_roughness_squared_threshold;
 
 	/* ambient occlusion */
 	float ao_factor;