mutter/clutter/cogl/cogl-mesh.h

/* cogl-mesh.h: Handle extensible arrays of vertex attributes
 * This file is part of Clutter
 *
 * Copyright (C) 2008  Intel Corporation.
 *
 * Authored by: Robert Bragg <bob@o-hand.com>
 *
 * 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/>.
 */

#if !defined(__COGL_H_INSIDE__) && !defined(CLUTTER_COMPILATION)
#error "Only <cogl/cogl.h> can be included directly."
#endif

#ifndef __COGL_MESH_H__
#define __COGL_MESH_H__

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

G_BEGIN_DECLS

/**
 * SECTION:cogl-mesh
 * @short_description: An API for submitting extensible arrays of vertex
 *		       attributes to OpenGL in a way that aims to minimise
 *		       copying or reformatting of the original data.
 *
 * The Mesh 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 with awareness of the specific hardware
 * being used then costly format conversion can also be avoided.
 *
 * They are designed to work on top of buffer objects and developers should
 * understand that mesh objects are not cheap to create but once they
 * have been submitted they are stored in GPU addressable memory and can
 * be quickly reused.
 *
 * Although this API does allow you to modify mesh objects after they have
 * been submitted to the GPU you must note that modification is still
 * not cheap, so if at all possible think of tricks that let you reuse
 * a static buffer. To help with this, it is possible to enable and disable
 * individual attributes cheaply.
 *
 * Take for example a mesh representing an elipse. If you were to submit
 * a mesh with color attributes, texture coordinates and normals, then
 * you would be able to draw an elipses in the following different ways
 * without creating a new mesh:
 * <itemizedlist>
 * <listitem>Flat colored elipse</listitem>
 * <listitem>Textured elipse</listitem>
 * <listitem>Smoothly lit textured elipse blended with the color.</listitem>
 * </itemizedlist>
 * 
 * Another trick that can be used is submitting a highly detailed mesh
 * and then using cogl_mesh_draw_range_elements to sample lower resolution
 * geometry out from a fixed mesh.
 *
 * The API doesn't currently give you any control over the actual buffer
 * objects that are created, but you can expect that when you first submit
 * your attributes they start off in one or more GL_STATIC_DRAW buffers.
 * If you then update some of your attributes; then these attributes will
 * normally be moved into new GL_DYNAMIC_DRAW draw buffers.
 */

/**
 * cogl_mesh_new:
 * @n_vertices: The number of vertices that will make up your mesh.
 *
 * This creates a Cogl handle for a new mesh that you can then start to add
 * attributes too.
 */
CoglHandle
cogl_mesh_new (guint n_vertices);

/**
 * cogl_mesh_add_attribute:
 * @handle: A Cogl mesh 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 in 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
 * @gl_type: Specifies the data type of each component (GL_BYTE, GL_UNSIGNED_BYTE,
 *	     GL_SHORT, GL_UNSIGNED_SHORT, GL_INT, GL_UNSIGNED_INT, GL_FLOAT or
 *	     GL_DOUBLE)
 * @normalized: If GL_TRUE, this specifies that values stored in an integer
 *		format should be mapped into the range [-1.0, 1.0] or [0.1, 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 call cogl_mesh_submit)
 *
 * This function lets you add an attribute to a mesh. You either use one
 * of the built-in names to add standard attributes, like positions, colors
 * and normals or you can add custom attributes for use in shaders.
 *
 * Note: The number of vertices declared when creating the mesh is used to
 * determine how many attribute values will be read from the supplied pointer.
 *
 * Note: the data supplied here isn't copied anywhere until you call
 * cogl_mesh_submit, so the supplied pointer must remain valid until then.
 * (This is an important optimisation since we can't create a buffer
 * object until we know about all the attributes, and repeatedly copying
 * large buffers of vertex data may be very costly) If you add attributes
 * after submitting then you will need to re-call cogl_mesh_submit to
 * commit the changes to the GPU. (Be carefull to minimize the number of
 * calls to cogl_mesh_submit though)
 *
 * Note: If you are interleving attributes it is assumed that that each
 * interleaved attribute starts no farther than +- stride bytes from
 * the other attributes it is interleved with. I.e. this is ok:
 * |-0-0-0-0-0-0-0-0-0-0|
 * This is not ok:
 * |- - - - -0-0-0-0-0-0 0 0 0 0|
 * (Though you can have multiple groups of interleved attributes)
 */
void
cogl_mesh_add_attribute (CoglHandle handle,
		         const char *attribute_name,
			 guint8 n_components,
			 GLenum gl_type,
			 gboolean normalized,
			 guint16 stride,
			 const void *pointer);

/**
 * cogl_mesh_delete_attribute:
 * @handle: A Cogl mesh handle
 * @attribute_name: The name of a previously added attribute
 *
 * This function deletes an attribute from a mesh. You will need to
 * call cogl_mesh_submit to commit this change to the GPU.
 */
void
cogl_mesh_delete_attribute (CoglHandle handle,
			    const char *attribute_name);

/**
 * cogl_mesh_enable_attribute:
 * @handle: A Cogl mesh handle
 * @attribute_name: The name of the attribute you want to enable
 *
 * This function enables a previosuly added attribute
 *
 * Since it is costly to create new mesh objects, then to make individual mesh
 * objects more reuseable it is possible to enable and disable attributes
 * before using a mesh for drawing.
 *
 * Note: You don't need to call cogl_mesh_submit after using this function
 */
void
cogl_mesh_enable_attribute (CoglHandle handle,
			    const char *attribute_name);

/**
 * cogl_mesh_disable_attribute:
 * @handle: A Cogl mesh handle
 * @attribute_name: The name of the attribute you want to disable
 *
 * This function disables a previosuly added attribute
 *
 * Since it is costly to create new mesh objects, then to make individual mesh
 * objects more reuseable it is possible to enable and disable attributes
 * before using a mesh for drawing.
 *
 * Note: You don't need to call cogl_mesh_submit after using this function
 */
void
cogl_mesh_disable_attribute (CoglHandle handle,
			     const char *attribute_name);

/**
 * cogl_mesh_draw_arrays:
 * @handle: A Cogl mesh handle
 * @mode: Specifies how the vertices should be interpreted, and should be
 *        a valid GL primitive type:
 *	  <itemizedlist>
 *	  <listitem>GL_POINTS</listitem>
 *	  <listitem>GL_LINE_STRIP</listitem>
 *	  <listitem>GL_LINE_LOOP</listitem>
 *	  <listitem>GL_LINES</listitem>
 *	  <listitem>GL_TRIANGLE_STRIP</listitem>
 *	  <listitem>GL_TRIANGLE_FAN</listitem>
 *	  <listitem>GL_TRIANGLES</listitem>
 *	  </itemizedlist>
 *	  (Note: only types available in GLES are listed)
 * @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 mesh object.
 */
void
cogl_mesh_draw_arrays (CoglHandle handle,
		       GLenum mode,
		       GLint first,
		       GLsizei count);

/**
 * cogl_mesh_draw_range_elements:
 * @handle: A Cogl mesh handle
 * @mode: Specifies how the vertices should be interpreted, and should be
 *        a valid GL primitive type:
 *	  <itemizedlist>
 *	  <listitem>GL_POINTS</listitem>
 *	  <listitem>GL_LINE_STRIP</listitem>
 *	  <listitem>GL_LINE_LOOP</listitem>
 *	  <listitem>GL_LINES</listitem>
 *	  <listitem>GL_TRIANGLE_STRIP</listitem>
 *	  <listitem>GL_TRIANGLE_FAN</listitem>
 *	  <listitem>GL_TRIANGLES</listitem>
 *	  </itemizedlist>
 *	  (Note: only types available in GLES are listed)
 * @start: Specifies the minimum vertex index contained in indices
 * @end: Specifies the maximum vertex index contained in indices
 * @count: Specifies the number of vertices you want to draw.
 * @type: Specifies the data type used for the indices, and must be
 *	  one of:
 *	  <itemizedlist>
 *	  <listitem>GL_UNSIGNED_BYTE</listitem>
 *	  <listitem>GL_UNSIGNED_SHORT</listitem>
 *        <listitem>GL_UNSIGNED_INT</listitem>
 *        </itemizedlist>
 * @indices: Specifies the address of your array of indices
 *
 * This function lets you use an array of indices to specify the vertices
 * within your mesh pbject that you want to draw.
 */
void
cogl_mesh_draw_range_elements (CoglHandle handle,
			       GLenum mode,
			       GLuint start,
			       GLuint end,
			       GLsizei count,
			       GLenum type,
			       const GLvoid *indices);

/**
 * cogl_mesh_submit:
 * @handle: A Cogl mesh handle
 *
 * This function copies all the user added attributes into a buffer object
 * managed by the OpenGL driver.
 *
 * After the attributes have been submitted, then you may no longer add or
 * remove attributes from a mesh, though you can enable or disable them.
 */
void
cogl_mesh_submit (CoglHandle handle);

/**
 * cogl_mesh_ref:
 * @handle: a @CoglHandle.
 *
 * Increment the reference count for a cogl mesh.
 *
 * Returns: the @handle.
 */
CoglHandle      cogl_mesh_ref              (CoglHandle          handle);

/**
 * cogl_mesh_unref:
 * @handle: a @CoglHandle.
 *
 * Deccrement the reference count for a cogl mesh.
 */
void            cogl_mesh_unref            (CoglHandle          handle);


G_END_DECLS

#endif /* __COGL_MESH_H__ */