Fix T57930 : Wrong hair shading in particle edit mode

Implement strand selection visualisation but without any shading.

I think this is not the overlay job to draw the strands shaded.

We can already view the children strands shaded for now but we might add
an option to draw the shaded strand instead of (or in addition to) the
guide strand.

1 files changed, 119 insertions, 53 deletions

diff --git a/source/blender/draw/intern/draw_cache_impl_particles.c b/source/blender/draw/intern/draw_cache_impl_particles.c
index 263aaa1ffdf..46ce115c382 100644
--- a/source/blender/draw/intern/draw_cache_impl_particles.c
+++ b/source/blender/draw/intern/draw_cache_impl_particles.c
@@ -80,6 +80,9 @@ typedef struct ParticleBatchCache {
 	/* Control points when in edit mode. */
 	ParticleHairCache edit_hair;
 
+	GPUVertBuf *edit_pos;
+	GPUBatch *edit_strands;
+
 	GPUVertBuf *edit_inner_pos;
 	GPUBatch *edit_inner_points;
 	int edit_inner_point_len;
@@ -100,6 +103,25 @@ typedef struct HairAttributeID {
 	uint ind;
 } HairAttributeID;
 
+typedef struct EditStrandData {
+	float pos[3];
+	uchar color;
+} EditStrandData;
+
+static GPUVertFormat *edit_points_vert_format_get(uint *r_pos_id, uint *r_color_id)
+{
+	static GPUVertFormat edit_point_format = { 0 };
+	static uint pos_id, color_id;
+	if (edit_point_format.attr_len == 0) {
+		/* Keep in sync with EditStrandData */
+		pos_id = GPU_vertformat_attr_add(&edit_point_format, "pos", GPU_COMP_F32, 3, GPU_FETCH_FLOAT);
+		color_id = GPU_vertformat_attr_add(&edit_point_format, "color", GPU_COMP_U8, 1, GPU_FETCH_INT_TO_FLOAT_UNIT);
+	}
+	*r_pos_id = pos_id;
+	*r_color_id = color_id;
+	return &edit_point_format;
+}
+
 static bool particle_batch_cache_valid(ParticleSystem *psys)
 {
 	ParticleBatchCache *cache = psys->batch_cache;
@@ -653,6 +675,52 @@ static void particle_batch_cache_fill_segments_proc_pos(
 	}
 }
 
+static float particle_key_select_ratio(const PTCacheEdit *edit, int strand, float t)
+{
+	const PTCacheEditPoint *point = &edit->points[strand];
+	float edit_key_seg_t = 1.0f / (point->totkey - 1);
+	if (t == 1.0) {
+		return (point->keys[point->totkey - 1].flag & PEK_SELECT) ? 1.0f : 0.0;
+	}
+	else {
+		float interp = t / edit_key_seg_t;
+		int index = (int)interp;
+		interp -= floorf(interp); /* Time between 2 edit key */
+		float s1 = (point->keys[index].flag & PEK_SELECT) ? 1.0f : 0.0;
+		float s2 = (point->keys[index+1].flag & PEK_SELECT) ? 1.0f : 0.0;
+		return s1 + interp * (s2 - s1);
+	}
+}
+
+static int particle_batch_cache_fill_segments_edit(
+        const PTCacheEdit *edit,
+        ParticleCacheKey **path_cache,
+        const int start_index,
+        const int num_path_keys,
+		GPUIndexBufBuilder *elb,
+        GPUVertBufRaw *attr_step)
+{
+	int curr_point = start_index;
+	for (int i = 0; i < num_path_keys; i++) {
+		ParticleCacheKey *path = path_cache[i];
+		if (path->segments <= 0) {
+			continue;
+		}
+		for (int j = 0; j <= path->segments; j++) {
+			EditStrandData *seg_data = (EditStrandData *)GPU_vertbuf_raw_step(attr_step);
+			copy_v3_v3(seg_data->pos, path[j].co);
+			float strand_t = (float)(j) / path->segments;
+			float selected = particle_key_select_ratio(edit, i, strand_t);
+			seg_data->color = (uchar)(0xFF * selected);
+			GPU_indexbuf_add_generic_vert(elb, curr_point);
+			curr_point++;
+		}
+		/* Finish the segment and add restart primitive. */
+		GPU_indexbuf_add_primitive_restart(elb);
+	}
+	return curr_point;
+}
+
 static int particle_batch_cache_fill_segments_indices(
         ParticleCacheKey **path_cache,
         const int start_index,
@@ -1366,6 +1434,46 @@ GPUBatch *DRW_particles_batch_cache_get_dots(Object *object, ParticleSystem *psy
 	return cache->point.points;
 }
 
+static void particle_batch_cache_ensure_edit_pos_and_seg(
+        PTCacheEdit *edit,
+        ParticleSystem *UNUSED(psys),
+        ModifierData *UNUSED(md),
+        ParticleHairCache *hair_cache)
+{
+	if (hair_cache->pos != NULL && hair_cache->indices != NULL) {
+		return;
+	}
+
+	GPU_VERTBUF_DISCARD_SAFE(hair_cache->pos);
+	GPU_INDEXBUF_DISCARD_SAFE(hair_cache->indices);
+
+	GPUVertBufRaw data_step;
+	GPUIndexBufBuilder elb;
+	uint pos_id, color_id;
+	GPUVertFormat *edit_point_format = edit_points_vert_format_get(&pos_id, &color_id);
+
+	hair_cache->pos = GPU_vertbuf_create_with_format(edit_point_format);
+	GPU_vertbuf_data_alloc(hair_cache->pos, hair_cache->point_len);
+	GPU_vertbuf_attr_get_raw_data(hair_cache->pos, pos_id, &data_step);
+
+	GPU_indexbuf_init_ex(
+	        &elb,
+	        GPU_PRIM_LINE_STRIP,
+	        hair_cache->elems_len, hair_cache->point_len,
+	        true);
+
+	if (edit != NULL && edit->pathcache != NULL) {
+		particle_batch_cache_fill_segments_edit(
+		        edit, edit->pathcache,
+		        0, edit->totcached,
+		        &elb, &data_step);
+	}
+	else {
+		BLI_assert(!"Hairs are not in edit mode!");
+	}
+	hair_cache->indices = GPU_indexbuf_build(&elb);
+}
+
 GPUBatch *DRW_particles_batch_cache_get_edit_strands(
         Object *object,
         ParticleSystem *psys,
@@ -1377,7 +1485,7 @@ GPUBatch *DRW_particles_batch_cache_get_edit_strands(
 	}
 	drw_particle_update_ptcache_edit(object, psys, edit);
 	ensure_seg_pt_count(edit, psys, &cache->edit_hair);
-	particle_batch_cache_ensure_pos_and_seg(edit, psys, NULL, &cache->edit_hair);
+	particle_batch_cache_ensure_edit_pos_and_seg(edit, psys, NULL, &cache->edit_hair);
 	cache->edit_hair.hairs = GPU_batch_create(
 	        GPU_PRIM_LINE_STRIP,
 	        cache->edit_hair.pos,
@@ -1400,17 +1508,6 @@ static void ensure_edit_inner_points_count(
 	}
 }
 
-static void edit_colors_get(
-        PTCacheEdit *edit,
-        float selected_color[4],
-        float normal_color[4])
-{
-	rgb_uchar_to_float(selected_color, edit->sel_col);
-	rgb_uchar_to_float(normal_color, edit->nosel_col);
-	selected_color[3] = 1.0f;
-	normal_color[3] = 1.0f;
-}
-
 static void particle_batch_cache_ensure_edit_inner_pos(
         PTCacheEdit *edit,
         ParticleBatchCache *cache)
@@ -1419,35 +1516,20 @@ static void particle_batch_cache_ensure_edit_inner_pos(
 		return;
 	}
 
-	static GPUVertFormat format = { 0 };
-	static uint pos_id, color_id;
-
-	GPU_VERTBUF_DISCARD_SAFE(cache->edit_inner_pos);
-
-	if (format.attr_len == 0) {
-		/* initialize vertex format */
-		pos_id = GPU_vertformat_attr_add(&format, "pos", GPU_COMP_F32, 3, GPU_FETCH_FLOAT);
-		color_id = GPU_vertformat_attr_add(&format, "color", GPU_COMP_F32, 4, GPU_FETCH_FLOAT);
-	}
+	uint pos_id, color_id;
+	GPUVertFormat *edit_point_format = edit_points_vert_format_get(&pos_id, &color_id);
 
-	cache->edit_inner_pos = GPU_vertbuf_create_with_format(&format);
+	cache->edit_inner_pos = GPU_vertbuf_create_with_format(edit_point_format);
 	GPU_vertbuf_data_alloc(cache->edit_inner_pos, cache->edit_inner_point_len);
 
-	float selected_color[4], normal_color[4];
-	edit_colors_get(edit, selected_color, normal_color);
-
 	int global_key_index = 0;
 	for (int point_index = 0; point_index < edit->totpoint; point_index++) {
 		const PTCacheEditPoint *point = &edit->points[point_index];
 		for (int key_index = 0; key_index < point->totkey - 1; key_index++) {
 			PTCacheEditKey *key = &point->keys[key_index];
+			uchar color = (key->flag & PEK_SELECT) ? 0xFF : 0x00;
 			GPU_vertbuf_attr_set(cache->edit_inner_pos, pos_id, global_key_index, key->world_co);
-			if (key->flag & PEK_SELECT) {
-				GPU_vertbuf_attr_set(cache->edit_inner_pos, color_id, global_key_index, selected_color);
-			}
-			else {
-				GPU_vertbuf_attr_set(cache->edit_inner_pos, color_id, global_key_index, normal_color);
-			}
+			GPU_vertbuf_attr_set(cache->edit_inner_pos, color_id, global_key_index, &color);
 			global_key_index++;
 		}
 	}
@@ -1490,33 +1572,18 @@ static void particle_batch_cache_ensure_edit_tip_pos(
 		return;
 	}
 
-	static GPUVertFormat format = { 0 };
-	static uint pos_id, color_id;
+	uint pos_id, color_id;
+	GPUVertFormat *edit_point_format = edit_points_vert_format_get(&pos_id, &color_id);
 
-	GPU_VERTBUF_DISCARD_SAFE(cache->edit_tip_pos);
-
-	if (format.attr_len == 0) {
-		/* initialize vertex format */
-		pos_id = GPU_vertformat_attr_add(&format, "pos", GPU_COMP_F32, 3, GPU_FETCH_FLOAT);
-		color_id = GPU_vertformat_attr_add(&format, "color", GPU_COMP_F32, 4, GPU_FETCH_FLOAT);
-	}
-
-	cache->edit_tip_pos = GPU_vertbuf_create_with_format(&format);
+	cache->edit_tip_pos = GPU_vertbuf_create_with_format(edit_point_format);
 	GPU_vertbuf_data_alloc(cache->edit_tip_pos, cache->edit_tip_point_len);
 
-	float selected_color[4], normal_color[4];
-	edit_colors_get(edit, selected_color, normal_color);
-
 	for (int point_index = 0; point_index < edit->totpoint; point_index++) {
 		const PTCacheEditPoint *point = &edit->points[point_index];
 		PTCacheEditKey *key = &point->keys[point->totkey - 1];
+		uchar color = (key->flag & PEK_SELECT) ? 0xFF : 0x00;
 		GPU_vertbuf_attr_set(cache->edit_tip_pos, pos_id, point_index, key->world_co);
-		if (key->flag & PEK_SELECT) {
-			GPU_vertbuf_attr_set(cache->edit_tip_pos, color_id, point_index, selected_color);
-		}
-		else {
-			GPU_vertbuf_attr_set(cache->edit_tip_pos, color_id, point_index, normal_color);
-		}
+		GPU_vertbuf_attr_set(cache->edit_tip_pos, color_id, point_index, &color);
 	}
 }
 
@@ -1582,6 +1649,5 @@ bool particles_ensure_procedural_data(
 		particle_batch_cache_ensure_procedural_indices(source.edit, source.psys, &cache->hair, thickness_res, subdiv);
 	}
 
-
 	return need_ft_update;
 }