G_BEGIN_DECLS
/**
* SECTION:cogl-attribute
* @short_description: Functions for declaring and drawing vertex
* attributes
*
* FIXME
*/
typedef struct _CoglAttribute CoglAttribute;
/**
* cogl_attribute_new:
* @attribute_buffer: The #CoglAttributeBuffer 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
* sizeof (MyVertex)
)
* @offset: The byte offset from the start of @attribute_buffer for
* the first attribute value. (Usually
* offsetof (MyVertex, component0)
* @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:
*
* "cogl_position_in" (used for vertex positions)
* "cogl_color_in" (used for vertex colors)
* "cogl_tex_coord0_in", "cogl_tex_coord1", ...
* (used for vertex texture coordinates)
* "cogl_normal_in" (used for vertex normals)
*
*
* 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 sizeof (MyVertex)
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 (2 * sizeof (float))
. 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 MyVertex
example above the @offset is the
* offset inside the MyVertex
structure to the first
* component of the attribute. For the texture coordinate attribute
* the offset would be offsetof (MyVertex, s)
or instead of
* using the offsetof macro you could use sizeof (float) * 3
.
* 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 (CoglAttributeBuffer *attribute_buffer,
const char *name,
gsize stride,
gsize offset,
int components,
CoglAttributeType type);
/**
* cogl_attribute_set_normalized:
* @attribute: A #CoglAttribute
* @normalized: The new value for the normalized property.
*
* Sets whether fixed point attribute types are mapped to the range
* 0→1. For example when this property is TRUE and a
* %COGL_ATTRIBUTE_TYPE_UNSIGNED_BYTE type is used then the value 255
* will be mapped to 1.0.
*
* The default value of this property depends on the name of the
* attribute. For the builtin properties cogl_color_in and
* cogl_normal_in it will default to TRUE and for all other names it
* will default to FALSE.
*
* Stability: unstable
* Since: 1.10
*/
void
cogl_attribute_set_normalized (CoglAttribute *attribute,
gboolean normalized);
/**
* cogl_attribute_get_normalized:
* @attribute: A #CoglAttribute
*
* Return value: the value of the normalized property set with
* cogl_attribute_set_normalized().
*
* Stability: unstable
* Since: 1.10
*/
gboolean
cogl_attribute_get_normalized (CoglAttribute *attribute);
/**
* cogl_attribute_get_buffer:
* @attribute: A #CoglAttribute
*
* Return value: the #CoglAttributeBuffer that was set with
* cogl_attribute_set_buffer() or cogl_attribute_new().
*
* Stability: unstable
* Since: 1.10
*/
CoglAttributeBuffer *
cogl_attribute_get_buffer (CoglAttribute *attribute);
/**
* cogl_attribute_set_buffer:
* @attribute: A #CoglAttribute
* @attribute_buffer: A #CoglAttributeBuffer
*
* Sets a new #CoglAttributeBuffer for the attribute.
*
* Stability: unstable
* Since: 1.10
*/
void
cogl_attribute_set_buffer (CoglAttribute *attribute,
CoglAttributeBuffer *attribute_buffer);
/**
* 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);
G_END_DECLS
#endif /* __COGL_ATTRIBUTE_H__ */