Cycles: Cleanup MultiGGX closure implementation

The implementation originally handled four different cases:
Regular glossy, glass, metallic fresnel glossy and diffuse.

However, only the first two are actually used currently. Therefore, this commit
removes the other two, which allows to simplify the code.

Additionally, due to the Principled BSDF, the function arguments are now
identical for glossy and glass, which allows to get rid of some ugly #ifdefs.

1 files changed, 6 insertions, 42 deletions

diff --git a/intern/cycles/kernel/closure/bsdf_microfacet_multi.h b/intern/cycles/kernel/closure/bsdf_microfacet_multi.h
index 30644946840..ec0c9823445 100644
--- a/intern/cycles/kernel/closure/bsdf_microfacet_multi.h
+++ b/intern/cycles/kernel/closure/bsdf_microfacet_multi.h
@@ -91,18 +91,15 @@ ccl_device_forceinline float3 mf_sample_vndf(const float3 wi, const float2 alpha
 	return normalize(make_float3(-slope_x, -slope_y, 1.0f));
 }
 
-/* === Phase functions: Glossy, Diffuse and Glass === */
+/* === Phase functions: Glossy and Glass === */
 
-/* Phase function for reflective materials, either without a fresnel term (for compatibility) or with the conductive fresnel term. */
-ccl_device_forceinline float3 mf_sample_phase_glossy(const float3 wi, float3 *n, float3 *k, float3 *weight, const float3 wm)
+/* Phase function for reflective materials. */
+ccl_device_forceinline float3 mf_sample_phase_glossy(const float3 wi, float3 *weight, const float3 wm)
 {
-	if(n && k)
-		*weight *= fresnel_conductor(dot(wi, wm), *n, *k);
-
 	return -wi + 2.0f * wm * dot(wi, wm);
 }
 
-ccl_device_forceinline float3 mf_eval_phase_glossy(const float3 w, const float lambda, const float3 wo, const float2 alpha, float3 *n, float3 *k)
+ccl_device_forceinline float3 mf_eval_phase_glossy(const float3 w, const float lambda, const float3 wo, const float2 alpha)
 {
 	if(w.z > 0.9999f)
 		return make_float3(0.0f, 0.0f, 0.0f);
@@ -123,30 +120,9 @@ ccl_device_forceinline float3 mf_eval_phase_glossy(const float3 w, const float l
 	else
 		phase *= D_ggx_aniso(wh, alpha);
 
-	if(n && k) {
-		/* Apply conductive fresnel term. */
-		return phase * fresnel_conductor(dotW_WH, *n, *k);
-	}
-
 	return make_float3(phase, phase, phase);
 }
 
-/* Phase function for rough lambertian diffuse surfaces. */
-ccl_device_forceinline float3 mf_sample_phase_diffuse(const float3 wm, const float randu, const float randv)
-{
-	float3 tm, bm;
-	make_orthonormals(wm, &tm, &bm);
-
-	float2 disk = concentric_sample_disk(randu, randv);
-	return disk.x*tm + disk.y*bm + safe_sqrtf(1.0f - disk.x*disk.x - disk.y*disk.y)*wm;
-}
-
-ccl_device_forceinline float3 mf_eval_phase_diffuse(const float3 w, const float3 wm)
-{
-	const float v = max(0.0f, dot(w, wm)) * M_1_PI_F;
-	return make_float3(v, v, v);
-}
-
 /* Phase function for dielectric transmissive materials, including both reflection and refraction according to the dielectric fresnel term. */
 ccl_device_forceinline float3 mf_sample_phase_glass(const float3 wi, const float eta, const float3 wm, const float randV, bool *outside)
 {
@@ -282,11 +258,6 @@ ccl_device_forceinline float mf_ggx_aniso_pdf(const float3 wi, const float3 wo,
 	return 0.25f * D_ggx_aniso(normalize(wi+wo), alpha) / ((1.0f + mf_lambda(wi, alpha)) * wi.z) + (1.0f - mf_ggx_albedo(sqrtf(alpha.x*alpha.y))) * wo.z;
 }
 
-ccl_device_forceinline float mf_diffuse_pdf(const float3 wo)
-{
-	return M_1_PI_F * wo.z;
-}
-
 ccl_device_forceinline float mf_glass_pdf(const float3 wi, const float3 wo, const float alpha, const float eta)
 {
 	float3 wh;
@@ -315,13 +286,6 @@ ccl_device_forceinline float mf_glass_pdf(const float3 wi, const float3 wo, cons
 #define MF_MULTI_GLASS
 #include "kernel/closure/bsdf_microfacet_multi_impl.h"
 
-/* The diffuse phase function is not implemented as a node yet. */
-#if 0
-#define MF_PHASE_FUNCTION diffuse
-#define MF_MULTI_DIFFUSE
-#include "kernel/closure/bsdf_microfacet_multi_impl.h"
-#endif
-
 #define MF_PHASE_FUNCTION glossy
 #define MF_MULTI_GLOSSY
 #include "kernel/closure/bsdf_microfacet_multi_impl.h"
@@ -428,7 +392,7 @@ ccl_device float3 bsdf_microfacet_multi_ggx_eval_reflect(const ShaderClosure *sc
 		*pdf = mf_ggx_aniso_pdf(localI, localO, make_float2(bsdf->alpha_x, bsdf->alpha_y));
 	else
 		*pdf = mf_ggx_pdf(localI, localO, bsdf->alpha_x);
-	return mf_eval_glossy(localI, localO, true, bsdf->extra->color, bsdf->alpha_x, bsdf->alpha_y, lcg_state, NULL, NULL, bsdf->ior, use_fresnel, bsdf->extra->cspec0);
+	return mf_eval_glossy(localI, localO, true, bsdf->extra->color, bsdf->alpha_x, bsdf->alpha_y, lcg_state, bsdf->ior, use_fresnel, bsdf->extra->cspec0);
 }
 
 ccl_device int bsdf_microfacet_multi_ggx_sample(KernelGlobals *kg, const ShaderClosure *sc, float3 Ng, float3 I, float3 dIdx, float3 dIdy, float randu, float randv, float3 *eval, float3 *omega_in, float3 *domega_in_dx, float3 *domega_in_dy, float *pdf, ccl_addr_space uint *lcg_state)
@@ -456,7 +420,7 @@ ccl_device int bsdf_microfacet_multi_ggx_sample(KernelGlobals *kg, const ShaderC
 	float3 localI = make_float3(dot(I, X), dot(I, Y), dot(I, Z));
 	float3 localO;
 
-	*eval = mf_sample_glossy(localI, &localO, bsdf->extra->color, bsdf->alpha_x, bsdf->alpha_y, lcg_state, NULL, NULL, bsdf->ior, use_fresnel, bsdf->extra->cspec0);
+	*eval = mf_sample_glossy(localI, &localO, bsdf->extra->color, bsdf->alpha_x, bsdf->alpha_y, lcg_state, bsdf->ior, use_fresnel, bsdf->extra->cspec0);
 	if(is_aniso)
 		*pdf = mf_ggx_aniso_pdf(localI, localO, make_float2(bsdf->alpha_x, bsdf->alpha_y));
 	else