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/*
* Cogl
*
* A Low Level GPU Graphics and Utilities API
*
* Copyright (C) 2010 Intel Corporation.
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy,
* modify, merge, publish, distribute, sublicense, and/or sell copies
* of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
*
*
* Authors:
* Robert Bragg <robert@linux.intel.com>
*/
#if !defined(__COGL_H_INSIDE__) && !defined(COGL_COMPILATION)
#error "Only <cogl/cogl.h> can be included directly."
#endif
#ifndef __COGL_INDICES_H__
#define __COGL_INDICES_H__
/* We forward declare the CoglIndices type here to avoid some circular
* dependency issues with the following headers.
*/
typedef struct _CoglIndices CoglIndices;
#include <cogl/cogl-index-buffer.h>
#ifdef COGL_HAS_GTYPE_SUPPORT
#include <glib-object.h>
#endif
COGL_BEGIN_DECLS
/**
* SECTION:cogl-indices
* @short_description: Describe vertex indices stored in a #CoglIndexBuffer.
*
* Indices allow you to avoid duplicating vertices in your vertex data
* by virtualizing your data and instead providing a sequence of index
* values that tell the GPU which data should be used for each vertex.
*
* If the GPU is given a sequence of indices it doesn't simply walk
* through each vertex of your data in order it will instead walk
* through the indices which can provide random access to the
* underlying data.
*
* Since it's very common to have duplicate vertices when describing a
* shape as a list of triangles it can often be a significant space
* saving to describe geometry using indices. Reducing the size of
* your models can make it cheaper to map them into the GPU by
* reducing the demand on memory bandwidth and may help to make better
* use of your GPUs internal vertex caching.
*
* For example, to describe a quadrilateral as 2 triangles for the GPU
* you could either provide data with 6 vertices or instead with
* indices you can provide vertex data for just 4 vertices and an
* index buffer that specfies the 6 vertices by indexing the shared
* vertices multiple times.
*
* |[
* CoglVertex2f quad_vertices[] = {
* {x0, y0}, //0 = top left
* {x1, y1}, //1 = bottom left
* {x2, y2}, //2 = bottom right
* {x3, y3}, //3 = top right
* };
* //tell the gpu how to interpret the quad as 2 triangles...
* unsigned char indices[] = {0, 1, 2, 0, 2, 3};
* ]|
*
* Even in the above illustration we see a saving of 10bytes for one
* quad compared to having data for 6 vertices and no indices but if
* you need to draw 100s or 1000s of quads then its really quite
* significant.
*
* Something else to consider is that often indices can be defined
* once and remain static while the vertex data may change for
* animations perhaps. That means you may be able to ignore the
* negligable cost of mapping your indices into the GPU if they don't
* ever change.
*
* The above illustration is actually a good example of static indices
* because it's really common that developers have quad mesh data that
* they need to display and we know exactly what that indices array
* needs to look like depending on the number of quads that need to be
* drawn. It doesn't matter how the quads might be animated and
* changed the indices will remain the same. Cogl even has a utility
* (cogl_get_rectangle_indices()) to get access to re-useable indices
* for drawing quads as above.
*/
#ifdef COGL_HAS_GTYPE_SUPPORT
/**
* cogl_indices_get_gtype:
*
* Returns: a #GType that can be used with the GLib type system.
*/
GType cogl_indices_get_gtype (void);
#endif
CoglIndices *
cogl_indices_new (CoglContext *context,
CoglIndicesType type,
const void *indices_data,
int n_indices);
CoglIndices *
cogl_indices_new_for_buffer (CoglIndicesType type,
CoglIndexBuffer *buffer,
size_t offset);
CoglIndexBuffer *
cogl_indices_get_buffer (CoglIndices *indices);
CoglIndicesType
cogl_indices_get_type (CoglIndices *indices);
size_t
cogl_indices_get_offset (CoglIndices *indices);
void
cogl_indices_set_offset (CoglIndices *indices,
size_t offset);
CoglIndices *
cogl_get_rectangle_indices (CoglContext *context, int n_rectangles);
/**
* cogl_is_indices:
* @object: A #CoglObject pointer
*
* Gets whether the given object references a #CoglIndices.
*
* Return value: %TRUE if the object references a #CoglIndices
* and %FALSE otherwise.
* Since: 1.10
* Stability: unstable
*/
CoglBool
cogl_is_indices (void *object);
COGL_END_DECLS
#endif /* __COGL_INDICES_H__ */
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