finished episode13

src/BufferClass.hs

@@ -0,0 +1,27 @@
+module BufferClass where
+
+import qualified Graphics.Rendering.OpenGL as GL
+
+import SDL (($=), get)
+
+-- this aims to be a typeclass for all used buffer objects throughout the
+-- tutorial.
+-- think of it as some kind of interface in the object oriented context
+class Buffer a where
+
+  -- what buffer target does te buffer bind to
+  target :: a -> GL.BufferTarget
+
+  -- what ID does the buffer have
+  glId :: a -> GL.BufferObject
+
+  -- bind the buffer object and fill it with data
+  initialize :: a -> IO ()
+
+  -- bind the buffer
+  bind :: a -> IO ()
+  bind buf = GL.bindBuffer (target buf) $= Just (glId buf)
+
+  -- unbind the buffer
+  unbind :: a -> IO ()
+  unbind buf = GL.bindBuffer (target buf) $= Nothing

src/IndexBuffer.hs

@@ -0,0 +1,58 @@
+module IndexBuffer where
+
+import qualified Graphics.Rendering.OpenGL as GL
+
+import SDL (($=), get)
+
+import Foreign
+
+-- internal imports
+
+import BufferClass
+
+-- layout of the IndexBuffer data object
+data IndexBuffer a = IndexBuffer
+  { iBufId    :: GL.BufferObject -- buffer id
+  , iBufSize  :: GL.GLsizeiptr   -- size of data
+  , iBufData  :: Ptr a           -- pointer to data
+  , iBufCount :: GL.GLuint       -- number of data elements
+  }
+
+-- instanciate typeclass from BufferClass and fill in missing implementations
+instance Buffer (IndexBuffer a) where
+
+  target _ = GL.ElementArrayBuffer
+
+  glId = iBufId
+
+  initialize buf = do
+    -- bind the buffer using the default iplementation of the typeclass
+    bind buf
+    -- fill in the data
+    GL.bufferData (target buf) $=
+      ( iBufSize buf
+      , iBufData buf
+      , GL.StaticDraw
+      )
+    -- release the buffer using the default implementation of the typeclass
+    unbind buf
+
+newIndexBuffer ::
+  (Storable a) =>      -- we have to be able to get a pointer to provided data
+  [a] ->               -- list of data elements
+  IO (IndexBuffer a)  -- newly built IndexBuffer data object
+newIndexBuffer list = do
+  -- create the buffer object in applicative style
+  buf <- IndexBuffer
+    -- generate the ID
+    <$> GL.genObjectName
+    -- compute buffer size
+    <*> pure (fromIntegral (length list * sizeOf (head list)))
+    -- make pointer out of list
+    <*> newArray list
+    -- get count
+    <*> pure (fromIntegral $ length list)
+  -- fill the data in to the buffer
+  initialize buf
+  -- return the data object
+  return buf

src/Main.hs

@@ -29,6 +29,12 @@ import qualified Data.List as L
 
 import System.Random (randomRIO)
 
+-- internal imports
+
+import BufferClass
+import VertexBuffer
+import IndexBuffer
+
 main :: IO ()
 main = do
 
@@ -81,22 +87,11 @@ main = do
       -- create draw order indices
       indices = [0, 1, 2, 2, 3, 0] :: [GL.GLuint]
 
-  -- create and bind buffer for vertices
-  buf <- GL.genObjectName
-  GL.bindBuffer GL.ArrayBuffer $= Just buf
+  -- construct new VertexBuffer and fill it with data
+  vbo <- newVertexBuffer vertexPositions
 
-  -- put vertices into the buffer
-    -- turn the list into a pointer
-  withArray vertexPositions $ \ptr ->
-    -- Feed the data to the buffer
-    GL.bufferData GL.ArrayBuffer $=
-      -- how much bytes of memory we are going to write (as an Int32)
-      ( fromIntegral $ length vertexPositions * sizeOf (undefined :: GL.GLfloat)
-      -- The pointer to the data
-      , ptr
-      -- The data's usage
-      , GL.StaticDraw
-      )
+  -- rebind the vertex buffer
+  bind vbo
 
   -- enable and specify data layout of the in-memory vertices
   GL.vertexAttribPointer (GL.AttribLocation 0) $=
@@ -113,22 +108,8 @@ main = do
     )
   GL.vertexAttribArray (GL.AttribLocation 0) $= GL.Enabled
 
-  -- create and bind buffer index buffer
-  ibo <- GL.genObjectName
-  GL.bindBuffer GL.ElementArrayBuffer $= Just ibo
-
-  -- put indices into index buffer
-    -- turn the list into a pointer
-  withArray indices $ \ptr -> do
-    -- Feed the data to the buffer
-    GL.bufferData GL.ElementArrayBuffer $=
-      -- how much bytes of memory we are going to write (as an Int32)
-      ( fromIntegral $ length indices * sizeOf (undefined :: GL.GLuint)
-      -- The pointer to the data
-      , ptr
-      -- The data's usage
-      , GL.StaticDraw
-      )
+  -- construct new IndexBuffer and fill it with data
+  ibo <- newIndexBuffer indices
 
   -- -- SHADERS
 
@@ -158,8 +139,8 @@ main = do
   -- -- UNBINDING ALL BUFFERS AND VERTEX ARRAYS
 
   GL.bindVertexArrayObject $= Nothing
-  GL.bindBuffer GL.ArrayBuffer $= Nothing
-  GL.bindBuffer GL.ElementArrayBuffer $= Nothing
+  unbind vbo
+  unbind ibo
   GL.currentProgram $= Nothing
 
   -- -- LOOPING
@@ -187,7 +168,7 @@ main = do
       -- rebind everything neccessary for draw call
       GL.bindVertexArrayObject $= Just vao
         -- (note the missing bindings to the vertex buffer and the attrib pointer)
-      GL.bindBuffer GL.ElementArrayBuffer $= Just ibo
+      bind ibo
       GL.currentProgram $= Just sp
 
       -- throw away previous errors
@@ -291,7 +272,7 @@ compileShaderSource type_ source = do
 
   if ok
   then
-    putStrLn (show type_ ++ ": compilation successfull!")
+    putStrLn (show type_ ++ ": compilation successful!")
   else do
     info <- get (GL.shaderInfoLog shaderObject)
     putStrLn (show type_ ++ ": compilation failed!\nInfo log says:")

src/VertexBuffer.hs

@@ -0,0 +1,55 @@
+module VertexBuffer where
+
+import qualified Graphics.Rendering.OpenGL as GL
+
+import SDL (($=), get)
+
+import Foreign
+
+-- internal imports
+
+import BufferClass
+
+-- layout of the VertexBuffer data object
+data VertexBuffer a = VertexBuffer
+  { vBufId   :: GL.BufferObject -- buffer id
+  , vBufSize :: GL.GLsizeiptr   -- size of data
+  , vBufData :: Ptr a           -- pointer to data
+  }
+
+-- instanciate typeclass from BufferClass and fill in missing implementations
+instance Buffer (VertexBuffer a) where
+
+  target _ = GL.ArrayBuffer
+
+  glId = vBufId
+
+  initialize buf = do
+    -- bind the buffer using the default iplementation of the typeclass
+    bind buf
+    -- fill in the data
+    GL.bufferData (target buf) $=
+      ( vBufSize buf
+      , vBufData buf
+      , GL.StaticDraw
+      )
+    -- release the buffer using the default implementation of the typeclass
+    unbind buf
+
+newVertexBuffer ::
+  (Storable a) =>      -- we have to be able to get a pointer to provided data
+  [a] ->               -- list of data elements
+  IO (VertexBuffer a)  -- newly built VertexBuffer data object
+newVertexBuffer list = do
+  -- create the buffer object in applicative style
+  buf <- VertexBuffer
+    -- generate the ID
+    <$> GL.genObjectName
+    -- compute buffer size
+    <*> pure (fromIntegral $ length list * sizeOf (head list))
+    -- make pointer out of list
+    <*> newArray list
+  -- fill the data in to the buffer
+  initialize buf
+  -- return the data object
+  return buf