Cycles: Automatically detect HDRI resolution by default and use non-square sampling map

The automatic mode checks all Enviroment Texture nodes and picks the largest image's resolution.
If there are no Enviroment Textures, it just uses the old default.

Also, the sampling map now isn't limited to square shapes. The automatic detection uses the exact image size,
the manual UI option now halves the value to get the height.

A default aspect ratio of 2:1 makes sense since this is what most HDRIs use.

Reviewers: brecht, sergey

Differential Revision: https://developer.blender.org/D3477

3 files changed, 28 insertions, 22 deletions

diff --git a/intern/cycles/kernel/kernel_emission.h b/intern/cycles/kernel/kernel_emission.h
index a5556c3be8f..524e2467ebc 100644
--- a/intern/cycles/kernel/kernel_emission.h
+++ b/intern/cycles/kernel/kernel_emission.h
@@ -319,9 +319,9 @@ ccl_device_noinline float3 indirect_background(KernelGlobals *kg,
 
 #ifdef __BACKGROUND_MIS__
 	/* check if background light exists or if we should skip pdf */
-	int res = kernel_data.integrator.pdf_background_res;
+	int res_x = kernel_data.integrator.pdf_background_res_x;
 
-	if(!(state->flag & PATH_RAY_MIS_SKIP) && res) {
+	if(!(state->flag & PATH_RAY_MIS_SKIP) && res_x) {
 		/* multiple importance sampling, get background light pdf for ray
 		 * direction, and compute weight with respect to BSDF pdf */
 		float pdf = background_light_pdf(kg, ray->P, ray->D);
diff --git a/intern/cycles/kernel/kernel_light.h b/intern/cycles/kernel/kernel_light.h
index ec7203d36eb..bb182ef1f25 100644
--- a/intern/cycles/kernel/kernel_light.h
+++ b/intern/cycles/kernel/kernel_light.h
@@ -143,12 +143,13 @@ float3 background_map_sample(KernelGlobals *kg, float randu, float randv, float
 	/* for the following, the CDF values are actually a pair of floats, with the
 	 * function value as X and the actual CDF as Y.  The last entry's function
 	 * value is the CDF total. */
-	int res = kernel_data.integrator.pdf_background_res;
-	int cdf_count = res + 1;
+	int res_x = kernel_data.integrator.pdf_background_res_x;
+	int res_y = kernel_data.integrator.pdf_background_res_y;
+	int cdf_width = res_x + 1;
 
 	/* this is basically std::lower_bound as used by pbrt */
 	int first = 0;
-	int count = res;
+	int count = res_y;
 
 	while(count > 0) {
 		int step = count >> 1;
@@ -163,24 +164,24 @@ float3 background_map_sample(KernelGlobals *kg, float randu, float randv, float
 	}
 
 	int index_v = max(0, first - 1);
-	kernel_assert(index_v >= 0 && index_v < res);
+	kernel_assert(index_v >= 0 && index_v < res_y);
 
 	float2 cdf_v = kernel_tex_fetch(__light_background_marginal_cdf, index_v);
 	float2 cdf_next_v = kernel_tex_fetch(__light_background_marginal_cdf, index_v + 1);
-	float2 cdf_last_v = kernel_tex_fetch(__light_background_marginal_cdf, res);
+	float2 cdf_last_v = kernel_tex_fetch(__light_background_marginal_cdf, res_y);
 
 	/* importance-sampled V direction */
 	float dv = inverse_lerp(cdf_v.y, cdf_next_v.y, randv);
-	float v = (index_v + dv) / res;
+	float v = (index_v + dv) / res_y;
 
 	/* this is basically std::lower_bound as used by pbrt */
 	first = 0;
-	count = res;
+	count = res_x;
 	while(count > 0) {
 		int step = count >> 1;
 		int middle = first + step;
 
-		if(kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_count + middle).y < randu) {
+		if(kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_width + middle).y < randu) {
 			first = middle + 1;
 			count -= step + 1;
 		}
@@ -189,15 +190,15 @@ float3 background_map_sample(KernelGlobals *kg, float randu, float randv, float
 	}
 
 	int index_u = max(0, first - 1);
-	kernel_assert(index_u >= 0 && index_u < res);
+	kernel_assert(index_u >= 0 && index_u < res_x);
 
-	float2 cdf_u = kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_count + index_u);
-	float2 cdf_next_u = kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_count + index_u + 1);
-	float2 cdf_last_u = kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_count + res);
+	float2 cdf_u = kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_width + index_u);
+	float2 cdf_next_u = kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_width + index_u + 1);
+	float2 cdf_last_u = kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_width + res_x);
 
 	/* importance-sampled U direction */
 	float du = inverse_lerp(cdf_u.y, cdf_next_u.y, randu);
-	float u = (index_u + du) / res;
+	float u = (index_u + du) / res_x;
 
 	/* compute pdf */
 	float denom = cdf_last_u.x * cdf_last_v.x;
@@ -223,19 +224,21 @@ ccl_device
 float background_map_pdf(KernelGlobals *kg, float3 direction)
 {
 	float2 uv = direction_to_equirectangular(direction);
-	int res = kernel_data.integrator.pdf_background_res;
+	int res_x = kernel_data.integrator.pdf_background_res_x;
+	int res_y = kernel_data.integrator.pdf_background_res_y;
+	int cdf_width = res_x + 1;
 
 	float sin_theta = sinf(uv.y * M_PI_F);
 
 	if(sin_theta == 0.0f)
 		return 0.0f;
 
-	int index_u = clamp(float_to_int(uv.x * res), 0, res - 1);
-	int index_v = clamp(float_to_int(uv.y * res), 0, res - 1);
+	int index_u = clamp(float_to_int(uv.x * res_x), 0, res_x - 1);
+	int index_v = clamp(float_to_int(uv.y * res_y), 0, res_y - 1);
 
 	/* pdfs in V direction */
-	float2 cdf_last_u = kernel_tex_fetch(__light_background_conditional_cdf, index_v * (res + 1) + res);
-	float2 cdf_last_v = kernel_tex_fetch(__light_background_marginal_cdf, res);
+	float2 cdf_last_u = kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_width + res_x);
+	float2 cdf_last_v = kernel_tex_fetch(__light_background_marginal_cdf, res_y);
 
 	float denom = cdf_last_u.x * cdf_last_v.x;
 
@@ -243,7 +246,7 @@ float background_map_pdf(KernelGlobals *kg, float3 direction)
 		return 0.0f;
 
 	/* pdfs in U direction */
-	float2 cdf_u = kernel_tex_fetch(__light_background_conditional_cdf, index_v * (res + 1) + index_u);
+	float2 cdf_u = kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_width + index_u);
 	float2 cdf_v = kernel_tex_fetch(__light_background_marginal_cdf, index_v);
 
 	return (cdf_u.x * cdf_v.x)/(M_2PI_F * M_PI_F * sin_theta * denom);
diff --git a/intern/cycles/kernel/kernel_types.h b/intern/cycles/kernel/kernel_types.h
index 72fbf7be557..5382213e6f7 100644
--- a/intern/cycles/kernel/kernel_types.h
+++ b/intern/cycles/kernel/kernel_types.h
@@ -1306,7 +1306,8 @@ typedef struct KernelIntegrator {
 	int num_all_lights;
 	float pdf_triangles;
 	float pdf_lights;
-	int pdf_background_res;
+	int pdf_background_res_x;
+	int pdf_background_res_y;
 	float light_inv_rr_threshold;
 
 	/* light portals */
@@ -1368,6 +1369,8 @@ typedef struct KernelIntegrator {
 	int start_sample;
 
 	int max_closures;
+
+	int pad1, pad2, pad3;
 } KernelIntegrator;
 static_assert_align(KernelIntegrator, 16);