Graphics.GPipe.PrimitiveArray

PrimitiveArrays (aka VAOs in OpenGl) are the main input to compiled shaders. A primitive array is created from one or more zipped vertex arrays. A primitive array may also be instanced, using one or more zipped vertex arrays as instance arrays. And lastly, an index array may also be used to pick vertices for the primitive array.

Any possible combination of interleaved or non-interleaved vertex buffers may be used, for example:

Buffer a = {(A,B),(A,B),(A,B)...} Buffer b = {(X,Y,Z),(X,Y,Z),(X,Y,Z),...}

  do
     aArr <- newVertexArray a        
     bArr <- newVertexArray b 
     let primArr = toPrimitiveArray TriangleList (zipVertices ((a,b) y -> (a,b,y)) aArr (fmap ((_,y,_) -> y) bArr))
 

will create a primitive array primArr with this layout: {(A,B,Y),(A,B,Y),(A,B,Y)...}

Vertex arrays

data VertexArray t a

A vertex array is the basic building block for a primitive array. It is created from the contents of a Buffer, but unlike a Buffer, it may be truncated, zipped with other vertex arrays, and even morphed into arrays of a different type with the provided Functor instance. A VertexArray t a has elements of type a, and t indicates whether the vertex array may be used as instances or not.

Instances

Functor (VertexArray t)

Methods

fmap :: (a -> b) -> VertexArray t a -> VertexArray t b

(<$) :: a -> VertexArray t b -> VertexArray t a

data Instances

A phantom type to indicate that a VertexArray may only be used for instances (in toPrimitiveArrayInstanced and toPrimitiveArrayIndexedInstanced).

newVertexArray :: Buffer os a -> Render os (VertexArray t a)

Create a VertexArray from a Buffer. The vertex array will have the same number of elements as the buffer, use takeVertices and dropVertices to make it smaller.

vertexArrayLength :: VertexArray t a -> Int

Retrieve the number of elements in a VertexArray.

zipVertices :: (a -> b -> c) -> VertexArray t a -> VertexArray t' b -> VertexArray (Combine t t') c

Zip two VertexArrays using the function given as first argument. If either of the argument VertexArrays are restriced to Instances only, then so will the resulting array be, as depicted by the Combine type family.

type family Combine t t' where ...

Equations

Combine () Instances = Instances

Combine Instances () = Instances

Combine Instances Instances = Instances

Combine () () = ()

takeVertices :: Int -> VertexArray t a -> VertexArray t a

takeVertices n a creates a shorter vertex array by taking the n first elements of the array a.

dropVertices :: Int -> VertexArray () a -> VertexArray t a

dropVertices n a creates a shorter vertex array by dropping the n first elements of the array a. The argument array a must not be constrained to only Instances.

replicateEach :: Int -> VertexArray t a -> VertexArray Instances a

replicateEach n a will create a longer vertex array, only to be used for instances, by replicating each element of the array a n times. E.g. replicateEach 3 {ABCD...} will yield {AAABBBCCCDDD...}. This is particulary useful before zipping the array with another that has a different replication rate.

Index arrays

data IndexArray

An index array is like a vertex array, but contains only integer indices. These indices must come from a tightly packed Buffer, hence the lack of a Functor instance and no conversion from VertexArrays.

newIndexArray :: forall os f b a. (BufferFormat b, Integral a, IndexFormat b ~ a) => Buffer os b -> Maybe a -> Render os IndexArray

Create an IndexArray from a Buffer of unsigned integers (as constrained by the closed IndexFormat type family instances). The index array will have the same number of elements as the buffer, use takeIndices and dropIndices to make it smaller. The Maybe a argument is used to optionally denote a primitive restart index.

type family IndexFormat a where ...

Equations

IndexFormat (B Word32) = Word32

IndexFormat (BPacked Word16) = Word16

IndexFormat (BPacked Word8) = Word8

indexArrayLength :: IndexArray -> Int

Numer of indices in an IndexArray.

takeIndices :: Int -> IndexArray -> IndexArray

takeIndices n a creates a shorter index array by taking the n first indices of the array a.

dropIndices :: Int -> IndexArray -> IndexArray

dropIndices n a creates a shorter index array by dropping the n first indices of the array a.

Primitive arrays

data PrimitiveArray p a

An array of primitives

Instances

Functor (PrimitiveArray p)

Methods

fmap :: (a -> b) -> PrimitiveArray p a -> PrimitiveArray p b

(<$) :: a -> PrimitiveArray p b -> PrimitiveArray p a

Monoid (PrimitiveArray p a)

Methods

mempty :: PrimitiveArray p a

mappend :: PrimitiveArray p a -> PrimitiveArray p a -> PrimitiveArray p a

mconcat :: [PrimitiveArray p a] -> PrimitiveArray p a

data PrimitiveTopology p where

Constructors

TriangleList :: PrimitiveTopology Triangles

TriangleStrip :: PrimitiveTopology Triangles

TriangleFan :: PrimitiveTopology Triangles

LineList :: PrimitiveTopology Lines

LineStrip :: PrimitiveTopology Lines

LineLoop :: PrimitiveTopology Lines

PointList :: PrimitiveTopology Points

data Triangles

data Lines

data Points

toPrimitiveArray :: PrimitiveTopology p -> VertexArray () a -> PrimitiveArray p a

toPrimitiveArrayIndexed :: PrimitiveTopology p -> IndexArray -> VertexArray () a -> PrimitiveArray p a

toPrimitiveArrayInstanced :: PrimitiveTopology p -> (a -> b -> c) -> VertexArray () a -> VertexArray t b -> PrimitiveArray p c

toPrimitiveArrayIndexedInstanced :: PrimitiveTopology p -> IndexArray -> (a -> b -> c) -> VertexArray () a -> VertexArray t b -> PrimitiveArray p c

Operations on buffer values

You may split up a B4 a, B3 a and B2 a value into its components, if the parts are representable buffer types (e.g. due to alignment, you may for instance not split a B4 Word8). Note that there are no functions to combine smaller parts together again.

toB22 :: forall a. (Storable a, BufferFormat (B2 a)) => B4 a -> (B2 a, B2 a)

Split up a B4 a into two B2 as.

toB3 :: forall a. (Storable a, BufferFormat (B3 a)) => B4 a -> B3 a

Discard the last component of a B4 a to get a B3 a.

toB21 :: forall a. (Storable a, BufferFormat (B a)) => B3 a -> (B2 a, B a)

Split up a B3 a into a B2 a and a B1 a.

toB12 :: forall a. (Storable a, BufferFormat (B a)) => B3 a -> (B a, B2 a)

Split up a B3 a into a B1 a and a B2 a.

toB11 :: forall a. (Storable a, BufferFormat (B a)) => B2 a -> (B a, B a)

Split up a B2 a into two B1 as.