Hair Info Length Attribute

Goal is to add the length attribute to the Hair Info node, for better control over color gradients or similar along the hair.

Reviewed By: #eevee_viewport, brecht

Differential Revision: https://developer.blender.org/D10481

1 files changed, 59 insertions, 28 deletions

diff --git a/source/blender/draw/intern/draw_cache_impl_particles.c b/source/blender/draw/intern/draw_cache_impl_particles.c
index 5c51f24a435..387c43741f7 100644
--- a/source/blender/draw/intern/draw_cache_impl_particles.c
+++ b/source/blender/draw/intern/draw_cache_impl_particles.c
@@ -46,6 +46,7 @@
 #include "ED_particle.h"
 
 #include "GPU_batch.h"
+#include "GPU_material.h"
 
 #include "DEG_depsgraph_query.h"
 
@@ -183,7 +184,9 @@ void particle_batch_cache_clear_hair(ParticleHairCache *hair_cache)
 {
   /* TODO: more granular update tagging. */
   GPU_VERTBUF_DISCARD_SAFE(hair_cache->proc_point_buf);
+  GPU_VERTBUF_DISCARD_SAFE(hair_cache->proc_length_buf);
   DRW_TEXTURE_FREE_SAFE(hair_cache->point_tex);
+  DRW_TEXTURE_FREE_SAFE(hair_cache->length_tex);
 
   GPU_VERTBUF_DISCARD_SAFE(hair_cache->proc_strand_buf);
   GPU_VERTBUF_DISCARD_SAFE(hair_cache->proc_strand_seg_buf);
@@ -609,7 +612,8 @@ static int particle_batch_cache_fill_segments(ParticleSystem *psys,
 
 static void particle_batch_cache_fill_segments_proc_pos(ParticleCacheKey **path_cache,
                                                         const int num_path_keys,
-                                                        GPUVertBufRaw *attr_step)
+                                                        GPUVertBufRaw *attr_step,
+                                                        GPUVertBufRaw *length_step)
 {
   for (int i = 0; i < num_path_keys; i++) {
     ParticleCacheKey *path = path_cache[i];
@@ -630,6 +634,8 @@ static void particle_batch_cache_fill_segments_proc_pos(ParticleCacheKey **path_
       seg_data[3] = total_len;
       co_prev = path[j].co;
     }
+    /* Assign length value*/
+    *(float *)GPU_vertbuf_raw_step(length_step) = total_len;
     if (total_len > 0.0f) {
       /* Divide by total length to have a [0-1] number. */
       for (int j = 0; j <= path->segments; j++, seg_data_first += 4) {
@@ -1079,40 +1085,64 @@ static void particle_batch_cache_ensure_procedural_indices(PTCacheEdit *edit,
 
 static void particle_batch_cache_ensure_procedural_pos(PTCacheEdit *edit,
                                                        ParticleSystem *psys,
-                                                       ParticleHairCache *cache)
+                                                       ParticleHairCache *cache,
+                                                       GPUMaterial *gpu_material)
 {
-  if (cache->proc_point_buf != NULL) {
-    return;
-  }
+  if (cache->proc_point_buf == NULL) {
+    /* initialize vertex format */
+    GPUVertFormat pos_format = {0};
+    uint pos_id = GPU_vertformat_attr_add(
+        &pos_format, "posTime", GPU_COMP_F32, 4, GPU_FETCH_FLOAT);
 
-  /* initialize vertex format */
-  GPUVertFormat format = {0};
-  uint pos_id = GPU_vertformat_attr_add(&format, "posTime", GPU_COMP_F32, 4, GPU_FETCH_FLOAT);
+    cache->proc_point_buf = GPU_vertbuf_create_with_format(&pos_format);
+    GPU_vertbuf_data_alloc(cache->proc_point_buf, cache->point_len);
 
-  cache->proc_point_buf = GPU_vertbuf_create_with_format(&format);
-  GPU_vertbuf_data_alloc(cache->proc_point_buf, cache->point_len);
+    GPUVertBufRaw pos_step;
+    GPU_vertbuf_attr_get_raw_data(cache->proc_point_buf, pos_id, &pos_step);
 
-  GPUVertBufRaw pos_step;
-  GPU_vertbuf_attr_get_raw_data(cache->proc_point_buf, pos_id, &pos_step);
+    GPUVertFormat length_format = {0};
+    uint length_id = GPU_vertformat_attr_add(
+        &length_format, "hairLength", GPU_COMP_F32, 1, GPU_FETCH_FLOAT);
 
-  if (edit != NULL && edit->pathcache != NULL) {
-    particle_batch_cache_fill_segments_proc_pos(edit->pathcache, edit->totcached, &pos_step);
-  }
-  else {
-    if ((psys->pathcache != NULL) &&
-        (!psys->childcache || (psys->part->draw & PART_DRAW_PARENT))) {
-      particle_batch_cache_fill_segments_proc_pos(psys->pathcache, psys->totpart, &pos_step);
+    cache->proc_length_buf = GPU_vertbuf_create_with_format(&length_format);
+    GPU_vertbuf_data_alloc(cache->proc_length_buf, cache->strands_len);
+
+    GPUVertBufRaw length_step;
+    GPU_vertbuf_attr_get_raw_data(cache->proc_length_buf, length_id, &length_step);
+
+    if (edit != NULL && edit->pathcache != NULL) {
+      particle_batch_cache_fill_segments_proc_pos(
+          edit->pathcache, edit->totcached, &pos_step, &length_step);
     }
-    if (psys->childcache) {
-      const int child_count = psys->totchild * psys->part->disp / 100;
-      particle_batch_cache_fill_segments_proc_pos(psys->childcache, child_count, &pos_step);
+    else {
+      if ((psys->pathcache != NULL) &&
+          (!psys->childcache || (psys->part->draw & PART_DRAW_PARENT))) {
+        particle_batch_cache_fill_segments_proc_pos(
+            psys->pathcache, psys->totpart, &pos_step, &length_step);
+      }
+      if (psys->childcache) {
+        const int child_count = psys->totchild * psys->part->disp / 100;
+        particle_batch_cache_fill_segments_proc_pos(
+            psys->childcache, child_count, &pos_step, &length_step);
+      }
     }
-  }
 
-  /* Create vbo immediately to bind to texture buffer. */
-  GPU_vertbuf_use(cache->proc_point_buf);
+    /* Create vbo immediately to bind to texture buffer. */
+    GPU_vertbuf_use(cache->proc_point_buf);
+    cache->point_tex = GPU_texture_create_from_vertbuf("part_point", cache->proc_point_buf);
+  }
 
-  cache->point_tex = GPU_texture_create_from_vertbuf("part_point", cache->proc_point_buf);
+  /* Checking hair length seperatly, only allocating gpu memory when needed */
+  if (gpu_material && cache->proc_length_buf != NULL && cache->length_tex == NULL) {
+    ListBase gpu_attrs = GPU_material_attributes(gpu_material);
+    LISTBASE_FOREACH (GPUMaterialAttribute *, attr, &gpu_attrs) {
+      if (attr->type == CD_HAIRLENGTH) {
+        GPU_vertbuf_use(cache->proc_length_buf);
+        cache->length_tex = GPU_texture_create_from_vertbuf("hair_length", cache->proc_length_buf);
+        break;
+      }
+    }
+  }
 }
 
 static void particle_batch_cache_ensure_pos_and_seg(PTCacheEdit *edit,
@@ -1649,6 +1679,7 @@ bool particles_ensure_procedural_data(Object *object,
                                       ParticleSystem *psys,
                                       ModifierData *md,
                                       ParticleHairCache **r_hair_cache,
+                                      GPUMaterial *gpu_material,
                                       int subdiv,
                                       int thickness_res)
 {
@@ -1666,9 +1697,9 @@ bool particles_ensure_procedural_data(Object *object,
   (*r_hair_cache)->final[subdiv].strands_res = 1 << (part->draw_step + subdiv);
 
   /* Refreshed on combing and simulation. */
-  if ((*r_hair_cache)->proc_point_buf == NULL) {
+  if ((*r_hair_cache)->proc_point_buf == NULL || (gpu_material && (*r_hair_cache)->length_tex == NULL)) {
     ensure_seg_pt_count(source.edit, source.psys, &cache->hair);
-    particle_batch_cache_ensure_procedural_pos(source.edit, source.psys, &cache->hair);
+    particle_batch_cache_ensure_procedural_pos(source.edit, source.psys, &cache->hair, gpu_material);
     need_ft_update = true;
   }