OpenGL-2.13.1.0: A binding for the OpenGL graphics system

Copyright | (c) Sven Panne 2002-2013
License | BSD3
Maintainer | Sven Panne <svenpanne@gmail.com>
Stability | stable
Portability | portable
Safe Haskell | None
Language | Haskell2010

Graphics.Rendering.OpenGL.GL.BeginEnd

Contents

- Begin and End Objects
- Polygon Edges

Description

This module corresponds to section 10.8 (Drawing Commands Using Begin and End) of the OpenGL 4.4 specs.

Synopsis

- renderPrimitive :: PrimitiveMode -> IO a -> IO a
- unsafeRenderPrimitive :: PrimitiveMode -> IO a -> IO a
- primitiveRestart :: IO ()
- data EdgeFlag
  - = BeginsInteriorEdge
  - | BeginsBoundaryEdge
- edgeFlag :: StateVar EdgeFlag

# Begin and End Objects

renderPrimitive :: PrimitiveMode -> IO a -> IO a

Delimit the vertices that define a primitive or a group of like primitives.

Only a subset of GL commands can be used in the delimited action: Those for specifying vertex coordinates (`vertex`, `vertexv`), vertex colors (`color`, `colorv`, `secondaryColor`, `secondaryColorv`, `index`, `indexv`), normal (`normal`, `normalv`), texture coordinates (`texCoord`, `texCoordv`, `multiTexCoord`, `multiTexCoordv`), and fog coordinates (`fogCoord`, `fogCoordv`). Additionally, `evalPoint1`, `evalPoint2`, `evalCoord1`, `evalCoord1v`, `evalCoord2`, `evalCoord2v`, `materialAmbient`, `materialDiffuse`, `materialAmbientAndDiffuse`, `materialSpecular`, `materialEmission`, `materialShininess`, `callList`, `callLists`, and setting `edgeFlag` are allowed. Writing the respective state variables is allowed in the delimited action, too.

Regardless of the chosen `PrimitiveMode`, there is no limit to the number of vertices that can be defined during a single `renderPrimitive`. Lines, triangles, quadrilaterals, and polygons that are incompletely specified are not drawn. Incomplete specification results when either too few vertices are provided to specify even a single primitive or when an incorrect multiple of vertices is specified. The incomplete primitive is ignored; the rest are drawn.

The minimum specification of vertices for each primitive is as follows: 1 for a point, 2 for a line, 3 for a triangle, 4 for a quadrilateral, and 3 for a polygon. Modes that require a certain multiple of vertices are `Lines` (2), `Triangles` (3), `Quads` (4), and `QuadStrip` (2).

unsafeRenderPrimitive :: PrimitiveMode -> IO a -> IO a

A more efficient, but potentially dangerous version of `renderPrimitive`: The given action is not allowed to throw an exception.

primitiveRestart :: IO ()

# Polygon Edges

data EdgeFlag

A vertex can begin an edge which lies in the interior of its polygon or on the polygon's boundary.

Constructors

BeginsInteriorEdge |
BeginsBoundaryEdge |

Instances

Eq EdgeFlag |
Ord EdgeFlag |
Show EdgeFlag |

edgeFlag :: StateVar EdgeFlag

Each vertex of a polygon, separate triangle, or separate quadrilateral specified during `renderPrimitive` is marked as the start of either a boundary or nonboundary (interior) edge.

The vertices of connected triangles and connected quadrilaterals are always marked as boundary, regardless of the value of the edge flag.

Boundary and nonboundary edge flags on vertices are significant only if `polygonMode` is set to `Point` or `Line`.

Note that the current edge flag can be updated at any time, in particular during `renderPrimitive`.