Add support for 8-bit vertex indices.

4 files changed, 72 insertions, 26 deletions

diff --git a/gfx/include/gfx/render_backend.h b/gfx/include/gfx/render_backend.h
index e037f78..785c4b9 100644
--- a/gfx/include/gfx/render_backend.h
+++ b/gfx/include/gfx/render_backend.h
@@ -27,7 +27,8 @@ typedef struct RenderBackend RenderBackend;
 
 /// Data type for vertex indices.
 /// Might need U32 for bigger models.
-typedef uint16_t VertexIndex;
+typedef uint8_t  VertexIndex8;
+typedef uint16_t VertexIndex16;
 typedef uint16_t VertexCount;
 
 /// Geometry drawing modes.
@@ -69,8 +70,11 @@ MAKE_BUFFER_VIEW(BufferViewU8, uint8_t)
 /// A buffer view for 16-bit unsigned integers.
 MAKE_BUFFER_VIEW(BufferViewU16, uint16_t)
 
-/// A buffer view for vertex indices.
-MAKE_BUFFER_VIEW(BufferViewIdx, uint16_t)
+/// A buffer view for 8-bit vertex indices.
+MAKE_BUFFER_VIEW(BufferViewIdx8, uint16_t)
+
+/// A buffer view for 16-bit vertex indices.
+MAKE_BUFFER_VIEW(BufferViewIdx16, uint16_t)
 
 /// Describes a piece of geometry.
 ///
@@ -91,10 +95,11 @@ typedef struct GeometryDesc {
     BufferViewU8    u8;
     BufferViewU16   u16;
   } weights; // vec4 or uvec4.
-  BufferViewIdx indices;
-  VertexCount   num_verts;
-  size_t        num_indices;
-  PrimitiveType type;
+  BufferViewIdx8  indices8;
+  BufferViewIdx16 indices16;
+  VertexCount     num_verts;
+  size_t          num_indices;
+  PrimitiveType   type;
 } GeometryDesc;
 
 /// Shader compiler define.
diff --git a/gfx/src/render/geometry.c b/gfx/src/render/geometry.c
index 0df6efb..7f3fc46 100644
--- a/gfx/src/render/geometry.c
+++ b/gfx/src/render/geometry.c
@@ -83,10 +83,9 @@ bool gfx_init_geometry(
       view_is_populated(desc->positions2d));
   assert(desc->num_verts > 0);
 
-  geometry->mode                 = primitive_type_to_gl(desc->type);
-  geometry->num_verts            = desc->num_verts;
-  geometry->num_indices          = desc->num_indices;
-  geometry->indices_offset_bytes = desc->indices.offset_bytes;
+  geometry->mode        = primitive_type_to_gl(desc->type);
+  geometry->num_verts   = desc->num_verts;
+  geometry->num_indices = desc->num_indices;
 
   glGenVertexArrays(1, &geometry->vao);
   glBindVertexArray(geometry->vao);
@@ -174,16 +173,31 @@ bool gfx_init_geometry(
 
   glBindBuffer(GL_ARRAY_BUFFER, 0);
 
-  if (view_is_populated(desc->indices)) {
+  if (view_is_populated(desc->indices8)) {
     assert(desc->num_indices > 0);
-    assert(desc->num_indices <= desc->indices.size_bytes / sizeof(VertexIndex));
-    geometry->indices =
-        get_or_make_buffer(render_backend, (const BufferView*)&desc->indices);
-    if (!geometry->indices) {
+    assert(
+        desc->num_indices <= desc->indices8.size_bytes / sizeof(VertexIndex8));
+    geometry->indices_offset_bytes = desc->indices8.offset_bytes;
+    geometry->indices8 =
+        get_or_make_buffer(render_backend, (const BufferView*)&desc->indices8);
+    if (!geometry->indices8) {
+      gfx_del_geometry(geometry);
+      return false;
+    }
+    assert(desc->indices8.size_bytes <= geometry->indices8->size_bytes);
+  } else if (view_is_populated(desc->indices16)) {
+    assert(desc->num_indices > 0);
+    assert(
+        desc->num_indices <=
+        desc->indices16.size_bytes / sizeof(VertexIndex16));
+    geometry->indices_offset_bytes = desc->indices16.offset_bytes;
+    geometry->indices16 =
+        get_or_make_buffer(render_backend, (const BufferView*)&desc->indices16);
+    if (!geometry->indices16) {
       gfx_del_geometry(geometry);
       return false;
     }
-    assert(desc->indices.size_bytes <= geometry->indices->size_bytes);
+    assert(desc->indices16.size_bytes <= geometry->indices16->size_bytes);
   }
 
   glBindVertexArray(0);
@@ -203,8 +217,13 @@ void gfx_render_geometry(const Geometry* geometry) {
   assert(geometry);
   assert(geometry->vao);
   glBindVertexArray(geometry->vao);
-  if (geometry->indices) {
-    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, geometry->indices->vbo);
+  if (geometry->indices8) {
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, geometry->indices8->vbo);
+    glDrawElements(
+        geometry->mode, geometry->num_indices, GL_UNSIGNED_BYTE,
+        (const void*)geometry->indices_offset_bytes);
+  } else if (geometry->indices16) {
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, geometry->indices16->vbo);
     glDrawElements(
         geometry->mode, geometry->num_indices, GL_UNSIGNED_SHORT,
         (const void*)geometry->indices_offset_bytes);
diff --git a/gfx/src/render/geometry.h b/gfx/src/render/geometry.h
index 38e716b..fb8f923 100644
--- a/gfx/src/render/geometry.h
+++ b/gfx/src/render/geometry.h
@@ -27,7 +27,8 @@ typedef struct Geometry {
   const Buffer* texcoords;
   const Buffer* joints;
   const Buffer* weights;
-  const Buffer* indices;
+  const Buffer* indices8;
+  const Buffer* indices16;
 } Geometry;
 
 /// Create new geometry.
diff --git a/gfx/src/util/scene.c b/gfx/src/util/scene.c
index 6f34922..40d6686 100644
--- a/gfx/src/util/scene.c
+++ b/gfx/src/util/scene.c
@@ -909,12 +909,33 @@ static bool load_meshes(
         const cgltf_buffer_view* view         = prim->indices->buffer_view;
         const cgltf_size         buffer_index = view->buffer - data->buffers;
         assert(buffer_index < data->buffers_count);
-        const Buffer* buffer               = buffers[buffer_index];
-        geometry_desc.indices.buffer       = buffer;
-        geometry_desc.indices.offset_bytes = accessor->offset + view->offset;
-        geometry_desc.indices.size_bytes   = view->size;
-        geometry_desc.indices.stride_bytes = view->stride;
-        geometry_desc.num_indices          = prim->indices->count;
+        const Buffer*    buffer = buffers[buffer_index];
+        const cgltf_size component_size =
+            get_component_size(accessor->component_type);
+        switch (component_size) {
+        case 1: {
+          BufferViewIdx8* indices   = &geometry_desc.indices8;
+          indices->buffer           = buffer;
+          indices->offset_bytes     = accessor->offset + view->offset;
+          indices->size_bytes       = view->size;
+          indices->stride_bytes     = view->stride;
+          geometry_desc.num_indices = prim->indices->count;
+          break;
+        }
+        case 2: {
+          BufferViewIdx16* indices  = &geometry_desc.indices16;
+          indices->buffer           = buffer;
+          indices->offset_bytes     = accessor->offset + view->offset;
+          indices->size_bytes       = view->size;
+          indices->stride_bytes     = view->stride;
+          geometry_desc.num_indices = prim->indices->count;
+          break;
+        }
+        default:
+          // TODO: Handle 32-bit indices.
+          assert(false);
+          break;
+        }
       }
 
       // Vertex attributes.