From c12966c5b69841f49713f97f3d9fa7ba99fc42e7 Mon Sep 17 00:00:00 2001
From: HampusM <hampus@hampusmat.com>
Date: Mon, 23 Oct 2023 20:25:42 +0200
Subject: feat(engine): add using element buffers

---
 engine/src/renderer/mod.rs | 59 +++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 53 insertions(+), 6 deletions(-)

(limited to 'engine/src/renderer')

diff --git a/engine/src/renderer/mod.rs b/engine/src/renderer/mod.rs
index f31196d..a02bbc2 100644
--- a/engine/src/renderer/mod.rs
+++ b/engine/src/renderer/mod.rs
@@ -5,7 +5,12 @@ use cstr::cstr;
 use glfw::WindowSize;
 
 use crate::object::Object;
-use crate::opengl::buffer::{Buffer, Usage};
+use crate::opengl::buffer::{
+    ArrayKind as ArrayBufferKind,
+    Buffer,
+    ElementArrayKind as ElementArrayBufferKind,
+    Usage as BufferUsage,
+};
 #[cfg(feature = "debug")]
 use crate::opengl::debug::{MessageSeverity, MessageSource, MessageType};
 use crate::opengl::shader::Program as ShaderProgram;
@@ -106,7 +111,21 @@ pub fn render<'obj>(objects: impl IntoIterator<Item = &'obj Object>)
             .set_uniform_matrix_4fv(cstr!("transform"), &obj.transform().as_matrix());
 
         obj.renderable().vertex_arr.bind(|vert_arr_curr_bound| {
-            VertexArray::draw(&vert_arr_curr_bound, PrimitiveKind::Triangles, 0, 3);
+            if let Some(index_info) = &obj.renderable().index_info {
+                VertexArray::draw_elements(
+                    &vert_arr_curr_bound,
+                    PrimitiveKind::Triangles,
+                    0,
+                    index_info.cnt,
+                );
+            } else {
+                VertexArray::draw_arrays(
+                    &vert_arr_curr_bound,
+                    PrimitiveKind::Triangles,
+                    0,
+                    3,
+                );
+            }
         });
     }
 }
@@ -122,29 +141,57 @@ pub struct Renderable
     shader_program: ShaderProgram,
     vertex_arr: VertexArray,
 
-    /// Vertex buffer has to live as long as the vertex array
-    _vertex_buffer: Buffer<Vertex>,
+    /// Vertex and index buffer has to live as long as the vertex array
+    _vertex_buffer: Buffer<Vertex, ArrayBufferKind>,
+    index_info: Option<IndexInfo>,
+}
+
+#[derive(Debug)]
+struct IndexInfo
+{
+    _buffer: Buffer<u32, ElementArrayBufferKind>,
+    cnt: u32,
 }
 
 impl Renderable
 {
-    pub fn new(shader_program: ShaderProgram, vertices: &[Vertex]) -> Self
+    pub fn new(
+        shader_program: ShaderProgram,
+        vertices: &[Vertex],
+        indices: Option<&[u32]>,
+    ) -> Self
     {
         let vertex_arr = VertexArray::new();
         let vertex_buffer = Buffer::new();
 
+        let mut index_info = None;
+
         vertex_arr.bind(|vert_arr_curr_bound| {
             vertex_buffer.bind(|vert_buf_curr_bound| {
-                Buffer::store(&vert_buf_curr_bound, vertices, Usage::Static);
+                Buffer::store(&vert_buf_curr_bound, vertices, BufferUsage::Static);
 
                 VertexArray::configure_attrs(&vert_arr_curr_bound, &vert_buf_curr_bound);
             });
+
+            if let Some(indices) = indices {
+                let new_index_buffer = Buffer::new();
+
+                new_index_buffer.bind(|index_buf_curr_bound| {
+                    Buffer::store(&index_buf_curr_bound, indices, BufferUsage::Static);
+                });
+
+                index_info = Some(IndexInfo {
+                    _buffer: new_index_buffer,
+                    cnt: indices.len().try_into().unwrap(),
+                });
+            }
         });
 
         Self {
             shader_program,
             vertex_arr,
             _vertex_buffer: vertex_buffer,
+            index_info,
         }
     }
 }
-- 
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