star-3d

commit 14e645c99da364a68e01c89a1dcf45318db4a432
parent 987a07025d74d01037c9abe4e62f710dd0bac91e
Author: Vincent Forest <vincent.forest@meso-star.com>
Date:   Fri,  7 Feb 2020 15:37:24 +0100

Add one float to the buffer of vertex positions

According to Embree, the last vertex position must be at least 16 bytes
length.

Diffstat:
M
src/s3d_mesh.c
 | 
16
+++++++++++++---

1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/src/s3d_mesh.c b/src/s3d_mesh.c
@@ -36,6 +36,10 @@
 
 #include <rsys/float3.h>
 
+/* Number of floats added to the vertex position in order to ensure the Embree
+ * vertex padding constraint */
+#define POSITION_PADDING 1
+
 /*******************************************************************************
  * Helper functions
  ******************************************************************************/
@@ -102,7 +106,8 @@ mesh_setup_positions
 
   if(attr->get == S3D_KEEP) {
     ASSERT(mesh->attribs[S3D_POSITION]);
-    ASSERT(darray_float_size_get(&mesh->attribs[S3D_POSITION]->data) == nverts*3);
+    ASSERT(darray_float_size_get
+      (&mesh->attribs[S3D_POSITION]->data) - POSITION_PADDING == nverts*3);
     return;
   }
 
@@ -114,7 +119,11 @@ mesh_setup_positions
   /* Allocate vertex positions */
   res = vertex_buffer_create(mesh->dev->allocator, &mesh->attribs[S3D_POSITION]);
   if(res != RES_OK) FATAL("Insufficient memory\n");
-  res = darray_float_resize(&mesh->attribs[S3D_POSITION]->data, nverts*3);
+
+  /* Embree requires that the last element is at least 16bytes length. One has
+   * thus to add some padding to the buffer of positions. */
+  res = darray_float_resize
+    (&mesh->attribs[S3D_POSITION]->data, nverts*3 + POSITION_PADDING);
   if(res != RES_OK) FATAL("Insufficient memory\n");
   mesh->attribs_type[S3D_POSITION] = S3D_FLOAT3;
 
@@ -314,7 +323,8 @@ mesh_get_nverts(const struct mesh* mesh)
     return 0;
 
   ASSERT(mesh->attribs_type[S3D_POSITION] == S3D_FLOAT3);
-  ncoords = darray_float_size_get(&mesh->attribs[S3D_POSITION]->data);
+  ncoords = darray_float_size_get
+    (&mesh->attribs[S3D_POSITION]->data) - POSITION_PADDING;
   ASSERT(ncoords % 3 == 0);
   return ncoords / 3;
 }