Viewport: Stereoscopy drawing is back

The viewport stereoscopy support helpers are finally ported to 2.80.

We now can scale the camera and the "stereo cameras" will scale
in the viewport as well (unlike 2.7x).

At the moment I disabled the drawing of the camera frame when
stereo is selected and you are looking through the camera.

It is to be fixed later, but for now it draws the border wrong.
In 2.79 this was not a problem because the camera frame was drawn
afterwards as a hack.

Viewport > Stereoscopy:
* Cameras
* Convergence plane
* Convergence plane alpha
* Stereoscopy volume
* Stereoscopy volume alpha

4 files changed, 234 insertions, 20 deletions

diff --git a/source/blender/blenkernel/BKE_camera.h b/source/blender/blenkernel/BKE_camera.h
index 91f03e46723..6cdd232e97c 100644
--- a/source/blender/blenkernel/BKE_camera.h
+++ b/source/blender/blenkernel/BKE_camera.h
@@ -141,6 +141,7 @@ struct Object *BKE_camera_multiview_render(struct Scene *scene, struct Object *c
 void           BKE_camera_multiview_view_matrix(struct RenderData *rd, const struct Object *camera, const bool is_left, float r_viewmat[4][4]);
 void           BKE_camera_multiview_model_matrix(struct RenderData *rd, const struct Object *camera, const char *viewname, float r_modelmat[4][4]);
 void           BKE_camera_multiview_model_matrix_scaled(struct RenderData *rd, const struct Object *camera, const char *viewname, float r_modelmat[4][4]);
+void           BKE_camera_multiview_window_matrix(struct RenderData *rd, const struct Object *camera, const char *viewname, float r_winmat[4][4]);
 float          BKE_camera_multiview_shift_x(struct RenderData *rd, const struct Object *camera, const char *viewname);
 void           BKE_camera_multiview_params(struct RenderData *rd, struct CameraParams *params, const struct Object *camera, const char *viewname);
 bool           BKE_camera_multiview_spherical_stereo(struct RenderData *rd, const struct Object *camera);
diff --git a/source/blender/blenkernel/intern/camera.c b/source/blender/blenkernel/intern/camera.c
index c39c8dec25d..d791ab01482 100644
--- a/source/blender/blenkernel/intern/camera.c
+++ b/source/blender/blenkernel/intern/camera.c
@@ -798,6 +798,22 @@ void BKE_camera_multiview_model_matrix_scaled(RenderData *rd, const Object *came
 	}
 }
 
+void BKE_camera_multiview_window_matrix(RenderData *rd, const Object *camera, const char *viewname, float r_winmat[4][4])
+{
+	CameraParams params;
+
+	/* Setup parameters */
+	BKE_camera_params_init(&params);
+	BKE_camera_params_from_object(&params, camera);
+	BKE_camera_multiview_params(rd, &params, camera, viewname);
+
+	/* Compute matrix, viewplane, .. */
+	BKE_camera_params_compute_viewplane(&params, rd->xsch, rd->ysch, rd->xasp, rd->yasp);
+	BKE_camera_params_compute_matrix(&params);
+
+	copy_m4_m4(r_winmat, params.winmat);
+}
+
 bool BKE_camera_multiview_spherical_stereo(RenderData *rd, const Object *camera)
 {
 	Camera *cam;
diff --git a/source/blender/draw/modes/object_mode.c b/source/blender/draw/modes/object_mode.c
index 90468658764..63273229096 100644
--- a/source/blender/draw/modes/object_mode.c
+++ b/source/blender/draw/modes/object_mode.c
@@ -231,6 +231,9 @@ typedef struct OBJECT_ShadingGroupList {
 	DRWShadingGroup *camera_clip_points;
 	DRWShadingGroup *camera_mist;
 	DRWShadingGroup *camera_mist_points;
+	DRWShadingGroup *camera_stereo_plane;
+	DRWShadingGroup *camera_stereo_volume;
+	DRWShadingGroup *camera_stereo_volume_wires;
 	ListBase camera_path;
 
 	/* Wire */
@@ -1258,6 +1261,15 @@ static void OBJECT_cache_init(void *vedata)
 		sgl->camera_clip_points = shgroup_distance_lines_instance(sgl->non_meshes, geom);
 		sgl->camera_mist_points = shgroup_distance_lines_instance(sgl->non_meshes, geom);
 
+		geom = DRW_cache_quad_get();
+		sgl->camera_stereo_plane = shgroup_instance_alpha(sgl->non_meshes, geom);
+
+		geom = DRW_cache_cube_get();
+		sgl->camera_stereo_volume = shgroup_instance_alpha(sgl->non_meshes, geom);
+
+		geom = DRW_cache_empty_cube_get();
+		sgl->camera_stereo_volume_wires = shgroup_instance(sgl->non_meshes, geom);
+
 		BLI_listbase_clear(&sgl->camera_path);
 
 		/* Texture Space */
@@ -1637,6 +1649,151 @@ static void batch_camera_path_free(ListBase *camera_paths)
 	}
 }
 
+static bool camera_view3d_is_stereo3d(Scene *scene, View3D *v3d)
+{
+	return (scene->r.scemode & R_MULTIVIEW) != 0 &&
+	       (v3d->stereo3d_flag);
+}
+
+static void camera_stereo3d(
+        OBJECT_ShadingGroupList *sgl,
+        Scene *scene, ViewLayer *view_layer, View3D *v3d,
+        Object *ob, Camera *cam,
+        const float vec[4][3], float drawsize, const float scale[3])
+{
+	const bool is_select = DRW_state_is_select();
+	static float drwtria_dummy[2][2][2] = {{{0}}};
+	const float fac = (cam->stereo.pivot == CAM_S3D_PIVOT_CENTER) ? 2.0f : 1.0f;
+	float origin[2][3] = {{0}};
+	const char *viewnames[2] = {STEREO_LEFT_NAME, STEREO_RIGHT_NAME};
+
+	const bool is_stereo3d_cameras = (v3d->stereo3d_flag & V3D_S3D_DISPCAMERAS) && (scene->r.views_format == SCE_VIEWS_FORMAT_STEREO_3D);
+	const bool is_stereo3d_plane = (v3d->stereo3d_flag & V3D_S3D_DISPPLANE) && (scene->r.views_format == SCE_VIEWS_FORMAT_STEREO_3D);
+	const bool is_stereo3d_volume = (v3d->stereo3d_flag & V3D_S3D_DISPVOLUME);
+
+	float *color;
+	DRW_object_wire_theme_get(ob, view_layer, &color);
+
+	for (int eye = 0; eye < 2; eye++) {
+		float obmat[4][4];
+		ob = BKE_camera_multiview_render(scene, ob, viewnames[eye]);
+
+		BKE_camera_multiview_model_matrix_scaled(&scene->r, ob, viewnames[eye], obmat);
+
+		copy_v2_v2(cam->drwcorners[eye][0], vec[0]);
+		copy_v2_v2(cam->drwcorners[eye][1], vec[1]);
+		copy_v2_v2(cam->drwcorners[eye][2], vec[2]);
+		copy_v2_v2(cam->drwcorners[eye][3], vec[3]);
+
+		cam->drwdepth[eye] = vec[0][2];
+
+		if (cam->stereo.convergence_mode == CAM_S3D_OFFAXIS) {
+			const float shift_x =
+			        ((BKE_camera_multiview_shift_x(&scene->r, ob, viewnames[eye]) - cam->shiftx) *
+			        (drawsize * scale[0] * fac));
+
+			for (int i = 0; i < 4; i++) {
+				cam->drwcorners[eye][i][0] += shift_x;
+			}
+		}
+
+		/* Dummy triangle, draw on top of existent lines so it is invisible. */
+		copy_v2_v2(drwtria_dummy[eye][0], cam->drwcorners[eye][0]);
+		copy_v2_v2(drwtria_dummy[eye][1], cam->drwcorners[eye][0]);
+
+		if (is_stereo3d_cameras) {
+			DRW_shgroup_call_dynamic_add(
+			        sgl->camera_frame, color, cam->drwcorners[eye],
+			        &cam->drwdepth[eye], cam->drwtria, obmat);
+
+			DRW_shgroup_call_dynamic_add(
+			        sgl->camera, color, cam->drwcorners[eye],
+			        &cam->drwdepth[eye], drwtria_dummy[eye], obmat);
+		}
+
+		/* Connecting line. */
+		mul_m4_v3(obmat, origin[eye]);
+	}
+
+	/* Draw connecting lines. */
+	if (is_stereo3d_cameras) {
+		DRW_shgroup_call_dynamic_add(sgl->relationship_lines, origin[0]);
+		DRW_shgroup_call_dynamic_add(sgl->relationship_lines, origin[1]);
+	}
+
+	/* Draw convergence plane. */
+	if (is_stereo3d_plane && !is_select) {
+		static float convergence_distance_neg;
+		float axis_center[3];
+		float convergence_plane[4][2];
+		float offset;
+
+		mid_v3_v3v3(axis_center, origin[0], origin[1]);
+
+		for (int i = 0; i < 4; i++) {
+			mid_v2_v2v2(convergence_plane[i], cam->drwcorners[0][i], cam->drwcorners[1][i]);
+		}
+
+		offset = cam->stereo.convergence_distance / cam->drwdepth[0];
+
+		for (int i = 0; i < 4; i++) {
+			convergence_plane[i][0] -= 2.0f * cam->shiftx;
+			convergence_plane[i][1] -= 2.0f * cam->shifty;
+			mul_v2_fl(convergence_plane[i], offset);
+		}
+
+		convergence_distance_neg = -cam->stereo.convergence_distance;
+		DRW_shgroup_call_dynamic_add(
+		        sgl->camera_frame, color, convergence_plane,
+		        &convergence_distance_neg, cam->drwtria, cam->drwnormalmat);
+
+		if (v3d->stereo3d_convergence_alpha > 0.0f) {
+			/* We are using a -1,1 quad for this shading group, so we need to
+			 * scale and transform it to match the convergence plane border. */
+			static float one = 1.0f;
+			float plane_mat[4][4], scale_mat[4][4];
+			float scale_factor[3] = {1.0f, 1.0f, 1.0f};
+			float color_plane[4] = {0.0f, 0.0f, 0.0f, v3d->stereo3d_convergence_alpha};
+
+			const float height = convergence_plane[1][1] - convergence_plane[0][1];
+			const float width = convergence_plane[2][0] - convergence_plane[0][0];
+
+			scale_factor[0] = width * 0.5f;
+			scale_factor[1] = height * 0.5f;
+
+			copy_m4_m4(plane_mat, cam->drwnormalmat);
+			translate_m4(plane_mat, 0.0f, 0.0f, -cam->stereo.convergence_distance);
+			size_to_mat4(scale_mat, scale_factor);
+			mul_m4_m4_post(plane_mat, scale_mat);
+
+			DRW_shgroup_call_dynamic_add(sgl->camera_stereo_plane, color_plane, &one, plane_mat);
+		}
+	}
+
+	/* Draw convergence volume. */
+	if (is_stereo3d_volume && !is_select) {
+		static float one = 1.0f;
+		float color_volume[3][4] = {{0.0f, 1.0f, 1.0f, v3d->stereo3d_volume_alpha},
+		                            {1.0f, 0.0f, 0.0f, v3d->stereo3d_volume_alpha},
+		                            {0.0f, 0.0f, 0.0f, 0.0f}};
+
+		for (int eye = 0; eye < 2; eye++) {
+			float winmat[4][4], viewinv[4][4], viewmat[4][4], persmat[4][4], persinv[4][4];
+			ob = BKE_camera_multiview_render(scene, ob, viewnames[eye]);
+
+			BKE_camera_multiview_window_matrix(&scene->r, ob, viewnames[eye], winmat);
+			BKE_camera_multiview_model_matrix(&scene->r, ob, viewnames[eye], viewinv);
+
+			invert_m4_m4(viewmat, viewinv);
+			mul_m4_m4m4(persmat, winmat, viewmat);
+			invert_m4_m4(persinv, persmat);
+
+			DRW_shgroup_call_dynamic_add(sgl->camera_stereo_volume, color_volume[eye], &one, persinv);
+			DRW_shgroup_call_dynamic_add(sgl->camera_stereo_volume_wires, color_volume[2], &one, persinv);
+		}
+	}
+}
+
 static void DRW_shgroup_camera(OBJECT_ShadingGroupList *sgl, Object *ob, ViewLayer *view_layer)
 {
 	const DRWContextState *draw_ctx = DRW_context_state_get();
@@ -1646,28 +1803,48 @@ static void DRW_shgroup_camera(OBJECT_ShadingGroupList *sgl, Object *ob, ViewLay
 
 	Camera *cam = ob->data;
 	const  Object *camera_object = DEG_get_evaluated_object(draw_ctx->depsgraph, v3d->camera);
+	const bool is_select = DRW_state_is_select();
 	const bool is_active = (ob == camera_object);
 	const bool look_through = (is_active && (rv3d->persp == RV3D_CAMOB));
+	const bool is_multiview = (scene->r.scemode & R_MULTIVIEW) != 0;
+	const bool is_stereo3d = is_active && camera_view3d_is_stereo3d(scene, v3d);
+	const bool is_stereo3d_view = (scene->r.views_format == SCE_VIEWS_FORMAT_STEREO_3D);
+	const bool is_stereo3d_cameras = (ob == scene->camera) &&
+	                                 is_multiview &&
+	                                 is_stereo3d_view &&
+	                                 (v3d->stereo3d_flag & V3D_S3D_DISPCAMERAS);
+	const bool is_selection_camera_stereo = is_select &&
+	                                        look_through && is_multiview &&
+	                                        is_stereo3d_view;
+
 	float *color;
 	DRW_object_wire_theme_get(ob, view_layer, &color);
 
 	float vec[4][3], asp[2], shift[2], scale[3], drawsize;
 
-	scale[0] = 1.0f / len_v3(ob->obmat[0]);
-	scale[1] = 1.0f / len_v3(ob->obmat[1]);
-	scale[2] = 1.0f / len_v3(ob->obmat[2]);
+	/* BKE_camera_multiview_model_matrix already accounts for scale, don't do it here. */
+	if (is_selection_camera_stereo) {
+		scale[0] = 1.0f;
+		scale[1] = 1.0f;
+		scale[2] = 1.0f;
+	}
+	else {
+		scale[0] = 1.0f / len_v3(ob->obmat[0]);
+		scale[1] = 1.0f / len_v3(ob->obmat[1]);
+		scale[2] = 1.0f / len_v3(ob->obmat[2]);
+	}
 
 	BKE_camera_view_frame_ex(scene, cam, cam->drawsize, false, scale,
 	                         asp, shift, &drawsize, vec);
 
 	/* Frame coords */
-	copy_v2_v2(cam->drwcorners[0], vec[0]);
-	copy_v2_v2(cam->drwcorners[1], vec[1]);
-	copy_v2_v2(cam->drwcorners[2], vec[2]);
-	copy_v2_v2(cam->drwcorners[3], vec[3]);
+	copy_v2_v2(cam->drwcorners[0][0], vec[0]);
+	copy_v2_v2(cam->drwcorners[0][1], vec[1]);
+	copy_v2_v2(cam->drwcorners[0][2], vec[2]);
+	copy_v2_v2(cam->drwcorners[0][3], vec[3]);
 
 	/* depth */
-	cam->drwdepth = vec[0][2];
+	cam->drwdepth[0] = vec[0][2];
 
 	/* tria */
 	cam->drwtria[0][0] = shift[0] + ((0.7f * drawsize) * scale[0]);
@@ -1675,22 +1852,38 @@ static void DRW_shgroup_camera(OBJECT_ShadingGroupList *sgl, Object *ob, ViewLay
 	cam->drwtria[1][0] = shift[0];
 	cam->drwtria[1][1] = shift[1] + ((1.1f * drawsize * (asp[1] + 0.7f)) * scale[1]);
 
-	if (look_through) {
+	if (look_through && !is_stereo3d_cameras) {
 		/* Only draw the frame. */
-		DRW_shgroup_call_dynamic_add(
-		        sgl->camera_frame, color, cam->drwcorners,
-		        &cam->drwdepth, cam->drwtria, ob->obmat);
+		float mat[4][4];
+		if (is_selection_camera_stereo) {
+			/* Make sure selection uses the same matrix for camera as the one used while viewing. */
+			const bool is_left = v3d->multiview_eye == STEREO_LEFT_ID;
+			BKE_camera_multiview_model_matrix(&scene->r, ob, is_left ? STEREO_LEFT_NAME : STEREO_RIGHT_NAME, mat);
+		}
+		else {
+			copy_m4_m4(mat, ob->obmat);
+		}
+
+		/* TODO (dfelinto): Disabling this for now since it is extremely wrong.
+		 * Besides selection and multiview still works bad even on its finest day. */
+		if (!is_multiview) {
+			DRW_shgroup_call_dynamic_add(
+			        sgl->camera_frame, color, cam->drwcorners[0],
+			        &cam->drwdepth[0], cam->drwtria, mat);
+		}
 	}
-	else {
-		DRW_shgroup_call_dynamic_add(
-		        sgl->camera, color, cam->drwcorners,
-		        &cam->drwdepth, cam->drwtria, ob->obmat);
+	else if (!look_through) {
+		if (!is_stereo3d_cameras) {
+			DRW_shgroup_call_dynamic_add(
+			        sgl->camera, color, cam->drwcorners[0],
+			        &cam->drwdepth[0], cam->drwtria, ob->obmat);
+		}
 
 		/* Active cam */
 		if (is_active) {
 			DRW_shgroup_call_dynamic_add(
 			        sgl->camera_tria, color,
-			        cam->drwcorners, &cam->drwdepth, cam->drwtria, ob->obmat);
+			        cam->drwcorners[0], &cam->drwdepth[0], cam->drwtria, ob->obmat);
 		}
 	}
 
@@ -1734,11 +1927,15 @@ static void DRW_shgroup_camera(OBJECT_ShadingGroupList *sgl, Object *ob, ViewLay
 		}
 	}
 
+	/* Stereo cameras drawing. */
+	if (is_stereo3d) {
+		camera_stereo3d(sgl, scene, view_layer, v3d, ob, cam, vec, drawsize, scale);
+	}
+
 	/* Motion Tracking. */
 	MovieClip *clip = BKE_object_movieclip_get(scene, ob, false);
 	if ((v3d->flag2 & V3D_SHOW_RECONSTRUCTION) && (clip != NULL)) {
 		BLI_assert(BLI_listbase_is_empty(&sgl->camera_path));
-		const bool is_select = DRW_state_is_select();
 		const bool is_solid_bundle = (v3d->bundle_drawtype == OB_EMPTY_SPHERE) &&
 		                             ((v3d->shading.type != OB_SOLID) ||
 		                              ((v3d->shading.flag & XRAY_FLAG(v3d)) == 0));
diff --git a/source/blender/makesdna/DNA_camera_types.h b/source/blender/makesdna/DNA_camera_types.h
index ab31bb6b9c5..bb80724c01a 100644
--- a/source/blender/makesdna/DNA_camera_types.h
+++ b/source/blender/makesdna/DNA_camera_types.h
@@ -109,9 +109,9 @@ typedef struct Camera {
 	char pad[7];
 
 	/* runtime only, used for drawing */
-	float drwcorners[4][2];
+	float drwcorners[2][4][2];
 	float drwtria[2][2];
-	float drwdepth, pad1;
+	float drwdepth[2];
 	float drwfocusmat[4][4];
 	float drwnormalmat[4][4];