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/*
* Cogl
*
* An object oriented GL/GLES Abstraction/Utility Layer
*
* Copyright (C) 2010 Intel Corporation.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library. If not, see <http://www.gnu.org/licenses/>.
*
*
*
* Authors:
* Robert Bragg <robert@linux.intel.com>
*/
#if !defined(__COGL_H_INSIDE__) && !defined(CLUTTER_COMPILATION)
#error "Only <cogl/cogl.h> can be included directly."
#endif
#ifndef __COGL_ATTRIBUTE_H__
#define __COGL_ATTRIBUTE_H__
#include <cogl/cogl-vertex-array.h>
#include <cogl/cogl-indices.h>
G_BEGIN_DECLS
/**
* SECTION:cogl-attribute
* @short_description: Functions for declaring and drawing vertex
* attributes
*
* FIXME
*/
typedef struct _CoglAttribute CoglAttribute;
/**
* cogl_attribute_new:
* @array: The #CoglVertexArray containing the actual attribute data
* @name: The name of the attribute (used to reference it from GLSL)
* @stride: The number of bytes to jump to get to the next attribute
* value for the next vertex. (Usually
* <pre>sizeof (MyVertex)</pre>)
* @offset: The byte offset from the start of @array for the first
* attribute value. (Usually
* <pre>offsetof (MyVertex, component0)</pre>
* @components: The number of components (e.g. 4 for an rgba color or
* 3 for and (x,y,z) position)
* @type: FIXME
*
* Describes the layout for a list of vertex attribute values (For
* example, a list of texture coordinates or colors).
*
* The @name is used to access the attribute inside a GLSL vertex
* shader and there are some special names you should use if they are
* applicable:
* <itemizedlist>
* <listitem>"cogl_position_in" (used for vertex positions)</listitem>
* <listitem>"cogl_color_in" (used for vertex colors)</listitem>
* <listitem>"cogl_tex_coord0_in", "cogl_tex_coord1", ...
* (used for vertex texture coordinates)</listitem>
* <listitem>"cogl_normal_in" (used for vertex normals)</listitem>
* </itemizedlist>
*
* The attribute values corresponding to different vertices can either
* be tightly packed or interleaved with other attribute values. For
* example it's common to define a structure for a single vertex like:
* |[
* typedef struct
* {
* float x, y, z; /<!-- -->* position attribute *<!-- -->/
* float s, t; /<!-- -->* texture coordinate attribute *<!-- -->/
* } MyVertex;
* ]|
*
* And then create an array of vertex data something like:
* |[
* MyVertex vertices[100] = { .... }
* ]|
*
* In this case, to describe either the position or texture coordinate
* attribute you have to move <pre>sizeof (MyVertex)</pre> bytes to
* move from one vertex to the next. This is called the attribute
* @stride. If you weren't interleving attributes and you instead had
* a packed array of float x, y pairs then the attribute stride would
* be <pre>(2 * sizeof (float))</pre>. So the @stride is the number of
* bytes to move to find the attribute value of the next vertex.
*
* Normally a list of attributes starts at the beginning of an array.
* So for the <pre>MyVertex</pre> example above the @offset is the
* offset inside the <pre>MyVertex</pre> structure to the first
* component of the attribute. For the texture coordinate attribute
* the offset would be <pre>offsetof (MyVertex, s)</pre> or instead of
* using the offsetof macro you could use <pre>sizeof (float) * 3</pre>.
* If you've divided your @array into blocks of non-interleved
* attributes then you will need to calculate the @offset as the
* number of bytes in blocks preceding the attribute you're
* describing.
*
* An attribute often has more than one component. For example a color
* is often comprised of 4 red, green, blue and alpha @components, and a
* position may be comprised of 2 x and y @components. You should aim
* to keep the number of components to a minimum as more components
* means more data needs to be mapped into the GPU which can be a
* bottlneck when dealing with a large number of vertices.
*
* Finally you need to specify the component data type. Here you
* should aim to use the smallest type that meets your precision
* requirements. Again the larger the type then more data needs to be
* mapped into the GPU which can be a bottlneck when dealing with
* a large number of vertices.
*
* Returns: A newly allocated #CoglAttribute describing the
* layout for a list of attribute values stored in @array.
*
* Since: 1.4
* Stability: Unstable
*/
/* XXX: look for a precedent to see if the stride/offset args should
* have a different order. */
CoglAttribute *
cogl_attribute_new (CoglVertexArray *array,
const char *name,
gsize stride,
gsize offset,
int components,
CoglAttributeType type);
/**
* cogl_is_attribute:
* @object: A #CoglObject
*
* Gets whether the given object references a #CoglAttribute.
*
* Return value: %TRUE if the handle references a #CoglAttribute,
* %FALSE otherwise
*/
gboolean
cogl_is_attribute (void *object);
void
cogl_draw_attributes (CoglVerticesMode mode,
int first_vertex,
int n_vertices,
...) G_GNUC_NULL_TERMINATED;
void
cogl_draw_attributes_array (CoglVerticesMode mode,
int first_vertex,
int n_vertices,
CoglAttribute **attributes);
void
cogl_draw_indexed_attributes (CoglVerticesMode mode,
int first_vertex,
int n_vertices,
CoglIndices *indices,
...) G_GNUC_NULL_TERMINATED;
void
cogl_draw_indexed_attributes_array (CoglVerticesMode mode,
int first_vertex,
int n_vertices,
CoglIndices *indices,
CoglAttribute **attributes);
G_END_DECLS
#endif /* __COGL_ATTRIBUTE_H__ */
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