[Bf-blender-cvs] [292f5ab7584] blender2.8: Eevee: Correct Mipmap texel alignment.

[Clément Foucault]

Commit: 292f5ab7584d6e9ba54893eaafd70d9ee8d1c3ce
Author: Clément Foucault
Date:   Wed Aug 9 15:20:18 2017 +0200
Branches: blender2.8
https://developer.blender.org/rB292f5ab7584d6e9ba54893eaafd70d9ee8d1c3ce

Eevee: Correct Mipmap texel alignment.

Since we are working with non power of 2 textures, the mipmap level UV does not line up perfectly.
This resulted in skewed filtering and bad sampling of the min/max depth buffer.

===================================================================

M	source/blender/draw/engines/eevee/eevee_effects.c
M	source/blender/draw/engines/eevee/eevee_private.h
M	source/blender/draw/engines/eevee/shaders/bsdf_common_lib.glsl
M	source/blender/draw/engines/eevee/shaders/effect_ssr_frag.glsl
M	source/blender/draw/engines/eevee/shaders/raytrace_lib.glsl

===================================================================

diff --git a/source/blender/draw/engines/eevee/eevee_effects.c b/source/blender/draw/engines/eevee/eevee_effects.c
index 7592e5c08d9..8475e280a32 100644
--- a/source/blender/draw/engines/eevee/eevee_effects.c
+++ b/source/blender/draw/engines/eevee/eevee_effects.c
@@ -493,6 +493,17 @@ void EEVEE_effects_init(EEVEE_SceneLayerData *sldata, EEVEE_Data *vedata)
 	                    (int)viewport_size[0] / 2, (int)viewport_size[1] / 2,
 	                    &texmin, 1);
 
+	/* Compute Mipmap texel alignement. */
+	for (int i = 0; i < 10; ++i) {
+		float mip_size[2] = {viewport_size[0], viewport_size[1]};
+		for (int j = 0; j < i; ++j) {
+			mip_size[0] = floorf(fmaxf(1.0f, mip_size[0] / 2.0f));
+			mip_size[1] = floorf(fmaxf(1.0f, mip_size[1] / 2.0f));
+		}
+		stl->g_data->mip_ratio[i][0] = viewport_size[0] / (mip_size[0] * powf(2.0f, floorf(log2f(floorf(viewport_size[0] / mip_size[0])))));
+		stl->g_data->mip_ratio[i][1] = viewport_size[1] / (mip_size[1] * powf(2.0f, floorf(log2f(floorf(viewport_size[1] / mip_size[1])))));
+	}
+
 	/* Cannot define 2 depth texture for one framebuffer. So allocate ourself. */
 	if (txl->maxzbuffer == NULL) {
 		txl->maxzbuffer = DRW_texture_create_2D((int)viewport_size[0] / 2, (int)viewport_size[1] / 2, DRW_TEX_DEPTH_24, DRW_TEX_MIPMAP, NULL);
@@ -754,6 +765,7 @@ void EEVEE_effects_cache_init(EEVEE_SceneLayerData *sldata, EEVEE_Data *vedata)
 		DRW_shgroup_uniform_buffer(grp, "maxzBuffer", &txl->maxzbuffer);
 		DRW_shgroup_uniform_buffer(grp, "minzBuffer", &stl->g_data->minzbuffer);
 		DRW_shgroup_uniform_vec4(grp, "viewvecs[0]", (float *)stl->g_data->viewvecs, 2);
+		DRW_shgroup_uniform_vec2(grp, "mipRatio[0]", (float *)stl->g_data->mip_ratio, 10);
 		DRW_shgroup_uniform_vec4(grp, "ssrParameters", &effects->ssr_quality, 1);
 		DRW_shgroup_uniform_int(grp, "rayCount", &effects->ssr_ray_count, 1);
 		DRW_shgroup_uniform_int(grp, "planar_count", &sldata->probes->num_planar, 1);
@@ -773,6 +785,7 @@ void EEVEE_effects_cache_init(EEVEE_SceneLayerData *sldata, EEVEE_Data *vedata)
 		DRW_shgroup_uniform_vec4(grp, "viewvecs[0]", (float *)stl->g_data->viewvecs, 2);
 		DRW_shgroup_uniform_int(grp, "planar_count", &sldata->probes->num_planar, 1);
 		DRW_shgroup_uniform_int(grp, "probe_count", &sldata->probes->num_render_cube, 1);
+		DRW_shgroup_uniform_vec2(grp, "mipRatio[0]", (float *)stl->g_data->mip_ratio, 10);
 		DRW_shgroup_uniform_float(grp, "borderFadeFactor", &effects->ssr_border_fac, 1);
 		DRW_shgroup_uniform_float(grp, "maxRoughness", &effects->ssr_max_roughness, 1);
 		DRW_shgroup_uniform_float(grp, "lodCubeMax", &sldata->probes->lod_cube_max, 1);
diff --git a/source/blender/draw/engines/eevee/eevee_private.h b/source/blender/draw/engines/eevee/eevee_private.h
index 906f6a0f454..4e17649ba42 100644
--- a/source/blender/draw/engines/eevee/eevee_private.h
+++ b/source/blender/draw/engines/eevee/eevee_private.h
@@ -470,6 +470,8 @@ typedef struct EEVEE_PrivateData {
 	float viewvecs[2][4];
 	/* For planar probes */
 	float texel_size[2];
+	/* To correct mip level texel mis-alignement */
+	float mip_ratio[10][2]; /* TODO put in a UBO */
 	/* For double buffering */
 	bool valid_double_buffer;
 	float prev_persmat[4][4];
diff --git a/source/blender/draw/engines/eevee/shaders/bsdf_common_lib.glsl b/source/blender/draw/engines/eevee/shaders/bsdf_common_lib.glsl
index f5ddbd0679c..27a08a98b4a 100644
--- a/source/blender/draw/engines/eevee/shaders/bsdf_common_lib.glsl
+++ b/source/blender/draw/engines/eevee/shaders/bsdf_common_lib.glsl
@@ -27,6 +27,8 @@ flat in int shFace; /* Shadow layer we are rendering to. */
 #define ViewMatrix      FaceViewMatrix[shFace]
 #endif
 
+uniform vec2 mipRatio[10];
+
 #define cameraForward   normalize(ViewMatrixInverse[2].xyz)
 #define cameraPos       ViewMatrixInverse[3].xyz
 #define cameraVec      ((ProjectionMatrix[3][3] == 0.0) ? normalize(cameraPos - worldPosition) : cameraForward)
diff --git a/source/blender/draw/engines/eevee/shaders/effect_ssr_frag.glsl b/source/blender/draw/engines/eevee/shaders/effect_ssr_frag.glsl
index 0374a4f9aa5..fb59c522deb 100644
--- a/source/blender/draw/engines/eevee/shaders/effect_ssr_frag.glsl
+++ b/source/blender/draw/engines/eevee/shaders/effect_ssr_frag.glsl
@@ -307,6 +307,10 @@ vec4 get_ssr_sample(
 	/* Estimate a cone footprint to sample a corresponding mipmap level. */
 	float mip = BRDF_BIAS * clamp(log2(cone_footprint * max(texture_size.x, texture_size.y)), 0.0, MAX_MIP) - 1.0;
 
+	/* Correct UVs for mipmaping mis-alignment */
+	float low_mip = floor(mip);
+	ref_uvs *= mix(mipRatio[int(low_mip)], mipRatio[int(low_mip + 1.0)], mip - low_mip);
+
 	/* Slide 54 */
 	float bsdf = bsdf_ggx(N, L, V, roughnessSquared);
 	float weight = step(1e-8, hit_co_pdf.w) * bsdf / max(1e-8, hit_co_pdf.w);
diff --git a/source/blender/draw/engines/eevee/shaders/raytrace_lib.glsl b/source/blender/draw/engines/eevee/shaders/raytrace_lib.glsl
index 855755adfe4..7afabfc5c3d 100644
--- a/source/blender/draw/engines/eevee/shaders/raytrace_lib.glsl
+++ b/source/blender/draw/engines/eevee/shaders/raytrace_lib.glsl
@@ -18,6 +18,8 @@ float sample_depth(vec2 uv, int index, float lod)
 		return textureLod(planarDepth, vec3(uv, index), 0.0).r;
 	}
 	else {
+		/* Correct UVs for mipmaping mis-alignment */
+		uv *= mipRatio[int(lod + 1.0)];
 		return textureLod(maxzBuffer, uv, lod).r;
 	}
 }