mutter/cogl-vertex-buffer.h

/*
 * Cogl
 *
 * An object oriented GL/GLES Abstraction/Utility Layer
 *
 * Copyright (C) 2008,2009 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, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * 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_VERTEX_BUFFER_H__
#define __COGL_VERTEX_BUFFER_H__

#include <glib.h>
#include <cogl/cogl-types.h>

G_BEGIN_DECLS

/**
 * SECTION:cogl-vertex-buffer
 * @short_description: An API for submitting extensible arrays of vertex
 *		       attributes to be mapped into the GPU for fast
 *		       drawing.
 *
 * For example to describe a textured triangle, you could create a new cogl
 * vertex buffer with 3 vertices, and then you might add 2 attributes for each
 * vertex:
 * <orderedlist>
 * <listitem>
 * a "gl_Position" describing the (x,y,z) position for each vertex.
 * </listitem>
 * <listitem>
 * a "gl_MultiTexCoord0" describing the (tx,ty) texture coordinates for each
 * vertex.
 * </listitem>
 * </orderedlist>
 *
 * The Vertex Buffer API is designed to be a fairly raw mechanism for
 * developers to be able to submit geometry to Cogl in a format that can be
 * directly consumed by an OpenGL driver and mapped into your GPU for fast
 * re-use. It is designed to avoid repeated validation of the attributes by the
 * driver; to minimize transport costs (e.g. considering indirect GLX
 * use-cases) and to potentially avoid repeated format conversions when
 * attributes are supplied in a format that is not natively supported by the
 * GPU.
 *
 * Although this API does allow you to modify attributes after they have been
 * submitted to the GPU you should be aware that modification is not that
 * cheap, since it implies validating the new data and potentially the
 * OpenGL driver will need to reformat it for the GPU.
 *
 * If at all possible think of tricks that let you re-use static attributes,
 * and if you do need to repeatedly update attributes (e.g. for some kind of
 * morphing geometry) then only update and re-submit the specific attributes
 * that have changed.
 */

/**
 * cogl_vertex_buffer_new:
 * @n_vertices: The number of vertices that your attributes will correspond to.
 *
 * Creates a new vertex buffer that you can use to add attributes.
 *
 * Return value: a new #CoglHandle
 */
CoglHandle
cogl_vertex_buffer_new (guint n_vertices);

/**
 * cogl_vertex_buffer_get_n_vertices:
 * @handle: A vertex buffer handle
 *
 * Retrieves the number of vertices that @handle represents
 *
 * Return value: the number of vertices
 */
guint
cogl_vertex_buffer_get_n_vertices (CoglHandle handle);

/**
 * CoglAttributeType:
 * @COGL_ATTRIBUTE_TYPE_BYTE: Data is the same size of a byte
 * @COGL_ATTRIBUTE_TYPE_UNSIGNED_BYTE: Data is the same size of an
 *   unsigned byte
 * @COGL_ATTRIBUTE_TYPE_SHORT: Data is the same size of a short integer
 * @COGL_ATTRIBUTE_TYPE_UNSIGNED_SHORT: Data is the same size of
 *   an unsigned short integer
 * @COGL_ATTRIBUTE_TYPE_FLOAT: Data is the same size of a float
 *
 * Data types for the components of cogl_vertex_buffer_add()
 *
 * Since: 1.0
 */
typedef enum _CoglAttributeType
{
  COGL_ATTRIBUTE_TYPE_BYTE = GL_BYTE,
  COGL_ATTRIBUTE_TYPE_UNSIGNED_BYTE = GL_UNSIGNED_BYTE,
  COGL_ATTRIBUTE_TYPE_SHORT = GL_SHORT,
  COGL_ATTRIBUTE_TYPE_UNSIGNED_SHORT = GL_UNSIGNED_SHORT,
  COGL_ATTRIBUTE_TYPE_FLOAT = GL_FLOAT
} CoglAttributeType;

/**
 * cogl_vertex_buffer_add:
 * @handle: A vertex buffer handle
 * @attribute_name: The name of your attribute. It should be a valid GLSL
 *		    variable name and standard attribute types must use one
 *		    of following built-in names: (Note: they correspond to the
 *		    built-in names of GLSL)
 *		    <itemizedlist>
 *		    <listitem>"gl_Color"</listitem>
 *		    <listitem>"gl_Normal"</listitem>
 *		    <listitem>"gl_MultiTexCoord0, gl_MultiTexCoord1, ..."</listitem>
 *		    <listitem>"gl_Vertex"</listitem>
 *		    </itemizedlist>
 *		    To support adding multiple variations of the same attribute
 *		    the name can have a detail component, E.g.
 *		    "gl_Color::active" or "gl_Color::inactive"
 * @n_components: The number of components per attribute and must be 1,2,3 or 4
 * @type: a #CoglAttributeType specifying the data type of each component.
 * @normalized: If GL_TRUE, this specifies that values stored in an integer
 *		format should be mapped into the range [-1.0, 1.0] or [0.0, 1.0]
 *		for unsigned values. If GL_FALSE they are converted to floats
 *		directly.
 * @stride: This specifies the number of bytes from the start of one attribute
 *	    value to the start of the next value (for the same attribute). So
 *	    for example with a position interleved with color like this:
 *	    XYRGBAXYRGBAXYRGBA, then if each letter represents a byte, the
 *	    stride for both attributes is 6. The special value 0 means the
 *	    values are stored sequentially in memory.
 * @pointer: This addresses the first attribute in the vertex array. (This
 *	     must remain valid until you either call
 *	     cogl_vertex_buffer_submit() or issue a draw call.)
 *
 * This function lets you add an attribute to a buffer. You either use one
 * of the built-in names such as "gl_Vertex", or "gl_MultiTexCoord0" to add
 * standard attributes, like positions, colors and normals or you can add
 * custom attributes for use in shaders.
 *
 * The number of vertices declared when calling cogl_vertex_buffer_new()
 * determines how many attribute values will be read from the supplied pointer.
 *
 * The data for your attribute isn't copied anywhere until you call
 * cogl_vertex_buffer_submit(), (or issue a draw call which automatically
 * submits pending attribute changes) so the supplied pointer must remain
 * valid until then. If you are updating an existing attribute (done by
 * re-adding it) then you still need to re-call cogl_vertex_buffer_submit() to
 * commit the changes to the GPU. (Be carefull to minimize the number of calls
 * to cogl_vertex_buffer_submit though.)
 *
 * Note: If you are interleving attributes it is assumed that each interleaved
 * attribute starts no farther than +- stride bytes from the other attributes
 * it is interleved with. I.e. this is ok:
 * <programlisting>
 * |-0-0-0-0-0-0-0-0-0-0|
 * </programlisting>
 * This is not ok:
 * <programlisting>
 * |- - - - -0-0-0-0-0-0 0 0 0 0|
 * </programlisting>
 * (Though you can have multiple groups of interleved attributes)
 */
void
cogl_vertex_buffer_add (CoglHandle         handle,
		        const char        *attribute_name,
			guint8             n_components,
			CoglAttributeType  type,
			gboolean           normalized,
			guint16            stride,
			const void        *pointer);

/**
 * cogl_vertex_buffer_delete:
 * @handle: A vertex buffer handle
 * @attribute_name: The name of a previously added attribute
 *
 * This function deletes an attribute from a buffer. You will need to
 * call cogl_vertex_buffer_submit() or issue a draw call to commit this
 * change to the GPU.
 */
void
cogl_vertex_buffer_delete (CoglHandle   handle,
			   const char  *attribute_name);

/**
 * cogl_vertex_buffer_submit:
 * @handle: A vertex buffer handle
 *
 * This function submits all the user added attributes to the GPU; once
 * submitted the attributes can be used for drawing.
 *
 * You should aim to minimize calls to this function since it implies
 * validating your data; it potentially incurs a transport cost (especially if
 * you are using GLX indirect rendering) and potentially a format conversion
 * cost if the GPU doesn't natively support any of the given attribute formats.
 */
void
cogl_vertex_buffer_submit (CoglHandle handle);

/**
 * cogl_vertex_buffer_disable:
 * @handle: A vertex buffer handle
 * @attribute_name: The name of the attribute you want to disable
 *
 * This function disables a previosuly added attribute.
 *
 * Since it can be costly to add and remove new attributes to buffers; to make
 * individual buffers more reuseable it is possible to enable and disable
 * attributes before using a buffer for drawing.
 *
 * You don't need to call cogl_vertex_buffer_submit() after using this function.
 */
void
cogl_vertex_buffer_disable (CoglHandle  handle,
			    const char *attribute_name);

/**
 * cogl_vertex_buffer_enable:
 * @handle: A vertex buffer handle
 * @attribute_name: The name of the attribute you want to enable
 *
 * This function enables a previosuly disabled attribute.
 *
 * Since it can be costly to add and remove new attributes to buffers; to make
 * individual buffers more reuseable it is possible to enable and disable
 * attributes before using a buffer for drawing.
 *
 * You don't need to call cogl_vertex_buffer_submit() after using this function
 */
void
cogl_vertex_buffer_enable (CoglHandle  handle,
			   const char *attribute_name);

/**
 * CoglVerticesMode:
 * @COGL_VERTICES_MODE_POINTS: FIXME, equivalent to %GL_POINTS
 * @COGL_VERTICES_MODE_LINE_STRIP: FIXME, equivalent to %GL_LINE_STRIP
 * @COGL_VERTICES_MODE_LINE_LOOP: FIXME, equivalent to %GL_LINE_LOOP
 * @COGL_VERTICES_MODE_LINES: FIXME, equivalent to %GL_LINES
 * @COGL_VERTICES_MODE_TRIANGLE_STRIP: FIXME, equivalent to %GL_TRIANGLE_STRIP
 * @COGL_VERTICES_MODE_TRIANGLE_FAN: FIXME, equivalent to %GL_TRIANGLE_FAN
 * @COGL_VERTICES_MODE_TRIANGLES: FIXME, equivalent to %GL_TRIANGLES
 *
 * How vertices passed to cogl_vertex_buffer_draw() and
 * cogl_vertex_buffer_draw_elements() should be interpreted
 *
 * Since: 1.0
 */
typedef enum _CoglVerticesMode
{
  COGL_VERTICES_MODE_POINTS = GL_POINTS,
  COGL_VERTICES_MODE_LINE_STRIP = GL_LINE_STRIP,
  COGL_VERTICES_MODE_LINE_LOOP = GL_LINE_LOOP,
  COGL_VERTICES_MODE_LINES = GL_LINES,
  COGL_VERTICES_MODE_TRIANGLE_STRIP = GL_TRIANGLE_STRIP,
  COGL_VERTICES_MODE_TRIANGLE_FAN = GL_TRIANGLE_FAN,
  COGL_VERTICES_MODE_TRIANGLES = GL_TRIANGLES
} CoglVerticesMode;

/**
 * cogl_vertex_buffer_draw:
 * @handle: A vertex buffer handle
 * @mode: A #CoglVerticesMode specifying how the vertices should be
 *        interpreted.
 * @first: Specifies the index of the first vertex you want to draw with
 * @count: Specifies the number of vertices you want to draw.
 *
 * This function lets you draw geometry using all or a subset of the
 * vertices in a vertex buffer.
 *
 * Any un-submitted attribute changes are automatically submitted before
 * drawing.
 */
void
cogl_vertex_buffer_draw (CoglHandle       handle,
		         CoglVerticesMode mode,
		         int              first,
		         int              count);

/**
 * CoglIndicesType:
 * @COGL_INDICES_TYPE_UNSIGNED_BYTE: Your indices are unsigned bytes
 * @COGL_INDICES_TYPE_UNSIGNED_SHORT: Your indices are unsigned shorts
 *
 * You should aim to use the smallest data type that gives you enough
 * range, since it reduces the size of your index array and can help
 * reduce the demand on memory bandwidth.
 */
typedef enum _CoglIndicesType
{
  COGL_INDICES_TYPE_UNSIGNED_BYTE,
  COGL_INDICES_TYPE_UNSIGNED_SHORT,
} CoglIndicesType;

/**
 * cogl_vertex_buffer_indices_new:
 * @indices_type: a #CoglIndicesType specifying the data type used for
 *                the indices.
 * @indices_array: Specifies the address of your array of indices
 * @indices_len: The number of indices in indices_array
 *
 * Depending on how much geometry you are submitting it can be worthwhile
 * optimizing the number of redundant vertices you submit. Using an index
 * array allows you to reference vertices multiple times, for example
 * during triangle strips.
 *
 * Returns: A CoglHandle for the indices which you can pass to
 *          cogl_vertex_buffer_draw_elements().
 */
CoglHandle
cogl_vertex_buffer_indices_new (CoglIndicesType  indices_type,
                                const void      *indices_array,
                                int              indices_len);

/**
 * cogl_vertex_buffer_indices_get_type:
 * @handle: An indices handle
 *
 * Queries back the data type used for the given indices
 *
 * Returns: The CoglIndicesType used
 */
CoglIndicesType
cogl_vertex_buffer_indices_get_type (CoglHandle indices);

/**
 * cogl_vertex_buffer_draw_elements:
 * @handle: A vertex buffer handle
 * @mode: A #CoglVerticesMode specifying how the vertices should be
 *        interpreted.
 * @indices: A CoglHandle for a set of indices allocated via
 *           cogl_vertex_buffer_indices_new ()
 * @min_index: Specifies the minimum vertex index contained in indices
 * @max_index: Specifies the maximum vertex index contained in indices
 * @indices_offset: An offset into named indices. The offset marks the first
 *                  index to use for drawing.
 * @count: Specifies the number of vertices you want to draw.
 *
 * This function lets you use an array of indices to specify the vertices
 * within your vertex buffer that you want to draw. The indices themselves
 * are created by calling cogl_vertex_buffer_indices_new ()
 *
 * Any un-submitted attribute changes are automatically submitted before
 * drawing.
 */
void
cogl_vertex_buffer_draw_elements (CoglHandle       handle,
			          CoglVerticesMode mode,
                                  CoglHandle       indices,
                                  int              min_index,
                                  int              max_index,
                                  int              indices_offset,
                                  int              count);

/**
 * cogl_vertex_buffer_ref:
 * @handle: a @CoglHandle.
 *
 * Increment the reference count for a vertex buffer
 *
 * Returns: the @handle.
 */
CoglHandle
cogl_vertex_buffer_ref (CoglHandle handle);

/**
 * cogl_vertex_buffer_unref:
 * @handle: a @CoglHandle.
 *
 * Decrement the reference count for a vertex buffer
 */
void
cogl_vertex_buffer_unref (CoglHandle handle);

/**
 * cogl_vertex_buffer_indices_get_for_quads:
 * @n_indices: the number of indices in the vertex buffer.
 *
 * Creates a vertex buffer containing the indices needed to draw pairs
 * of triangles from a list of vertices grouped as quads. There will
 * be at least @n_indices entries in the buffer (but there may be
 * more).
 *
 * The indices will follow this pattern:
 *
 * 0, 1, 2, 0, 2, 3, 4, 5, 6, 4, 6, 7 ... etc
 *
 * For example, if you submit vertices for a quad like this:
 *
 * |[
 *    0        3
 *     ########
 *     #      #
 *     #      #
 *     ########
 *    1        2
 * ]|
 *
 * Then you can request 6 indices to render two triangles like this:
 *
 * |[
 *    0           0        3
 *     ##          ########
 *     # ##          ##   #
 *     #   ##          ## #
 *     ########          ##
 *    1        2           2
 * ]|
 *
 * Returns: A %CoglHandle containing the indices. The handled is
 * owned by Cogl and should not be modified or unref'd.
 */
CoglHandle
cogl_vertex_buffer_indices_get_for_quads (guint n_indices);

G_END_DECLS

#endif /* __COGL_VERTEX_BUFFER_H__ */