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e338245827
This better reflects the fact that the api manages sets of vertex attributes, and the attributes really have no implied form. It is only when you use the attributes to draw that they become mesh like; when you specify how they should be interpreted, e.g. as triangle lists or fans etc. This rename frees up the term "mesh", which can later be applied to a concept slightly more fitting. E.g. at some point it would be nice to have a higher level abstraction that sits on top of cogl vertex buffers that adds the concept of faces. (Somthing like Blender's mesh objects.) There have also been some discussions over particle engines, and these can be defined in terms of emitter faces; so some other kind of mesh abstraction might be usefull here.
309 lines
11 KiB
C
309 lines
11 KiB
C
/*
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* Cogl.
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*
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* An OpenGL/GLES Abstraction/Utility Layer
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*
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* Vertex Buffer API: Handle extensible arrays of vertex attributes
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*
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* Copyright (C) 2008 Intel Corporation.
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*
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* Authored by: Robert Bragg <robert@linux.intel.com>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library. If not, see <http://www.gnu.org/licenses/>.
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*/
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#if !defined(__COGL_H_INSIDE__) && !defined(CLUTTER_COMPILATION)
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#error "Only <cogl/cogl.h> can be included directly."
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#endif
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#ifndef __COGL_VERTEX_BUFFER_H__
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#define __COGL_VERTEX_BUFFER_H__
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#include <glib.h>
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#include <cogl/cogl-types.h>
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G_BEGIN_DECLS
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/**
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* SECTION:cogl-vertex-buffer
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* @short_description: An API for submitting extensible arrays of vertex
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* attributes to OpenGL in a way that aims to minimise
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* copying or reformatting of the original data.
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*
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* The Attributes Buffer API is designed to be a fairly raw mechanism for
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* developers to be able to submit geometry to Cogl in a format that can be
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* directly consumed by an OpenGL driver and with awareness of the specific
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* hardware being used then costly format conversion can also be avoided.
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*
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* They are designed to work on top of buffer objects and developers should
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* understand that attribute buffers are not that cheap to create but once they
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* have been submitted they can be stored in GPU addressable memory and can
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* be quickly reused.
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*
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* Although this API does allow you to modify attribute buffers after they have
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* been submitted to the GPU you must note that modification is also not that
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* cheap, so if at all possible think of tricks that let you reuse a static
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* buffer. To help with this, it is possible to enable and disable individual
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* attributes cheaply.
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*
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* Take for example attributes representing an elipse. If you were to submit
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* color attributes, texture coordinates and normals, then you would be able
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* to draw an elipses in the following different ways without modifying
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* the vertex buffer, only by changing your source material.
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* <itemizedlist>
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* <listitem>Flat colored elipse</listitem>
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* <listitem>Textured elipse</listitem>
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* <listitem>Smoothly lit textured elipse blended with the color.</listitem>
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* </itemizedlist>
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*
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* Another trick that can be used is submitting highly detailed vertices and
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* then using cogl_vertex_buffer_draw_range_elements to sample sub-sets of
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* the geometry or lower resolution geometry out from a fixed buffer.
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*
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* The API doesn't currently give you any control over the actual OpenGL buffer
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* objects that are created, but you can expect that when you first submit
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* your attributes they start off in one or more GL_STATIC_DRAW buffers.
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* If you then update some of your attributes; then these attributes will
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* normally be moved into new GL_DYNAMIC_DRAW draw buffers.
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*/
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/**
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* cogl_vertex_buffer_new:
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* @n_vertices: The number of vertices that your attributes will correspond to.
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*
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* This creates a Cogl handle for a new vertex buffer that you can then start
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* to add attributes too.
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*/
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CoglHandle
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cogl_vertex_buffer_new (guint n_vertices);
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/**
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* cogl_vertex_buffer_add:
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* @handle: A vertex buffer handle
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* @attribute_name: The name of your attribute. It should be a valid GLSL
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* variable name and standard attribute types must use one
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* of following built-in names: (Note: they correspond to the
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* built-in names in GLSL)
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* <itemizedlist>
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* <listitem>"gl_Color"</listitem>
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* <listitem>"gl_Normal"</listitem>
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* <listitem>"gl_MultiTexCoord0, gl_MultiTexCoord1, ..."</listitem>
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* <listitem>"gl_Vertex"</listitem>
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* </itemizedlist>
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* To support adding multiple variations of the same attribute
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* the name can have a detail component, E.g.
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* "gl_Color::active" or "gl_Color::inactive"
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* @n_components: The number of components per attribute and must be 1,2,3 or 4
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* @gl_type: Specifies the data type of each component (GL_BYTE, GL_UNSIGNED_BYTE,
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* GL_SHORT, GL_UNSIGNED_SHORT, GL_INT, GL_UNSIGNED_INT, GL_FLOAT or
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* GL_DOUBLE)
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* @normalized: If GL_TRUE, this specifies that values stored in an integer
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* format should be mapped into the range [-1.0, 1.0] or [0.1, 1.0]
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* for unsigned values. If GL_FALSE they are converted to floats
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* directly.
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* @stride: This specifies the number of bytes from the start of one attribute
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* value to the start of the next value (for the same attribute). So
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* for example with a position interleved with color like this:
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* XYRGBAXYRGBAXYRGBA, then if each letter represents a byte, the
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* stride for both attributes is 6. The special value 0 means the
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* values are stored sequentially in memory.
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* @pointer: This addresses the first attribute in the vertex array. (This
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* must remain valid until you call cogl_vertex_buffer_submit)
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*
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* This function lets you add an attribute to a buffer. You either use one
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* of the built-in names to add standard attributes, like positions, colors
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* and normals or you can add custom attributes for use in shaders.
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*
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* Note: The number of vertices declared when first creating the vertex
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* buffer is used to determine how many attribute values will be read from the
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* supplied pointer.
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*
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* Note: the data supplied here isn't copied anywhere until you call
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* cogl_vertex_buffer_submit, so the supplied pointer must remain valid
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* until then.
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* (This is an important optimisation since we can't create the underlying
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* OpenGL buffer object until we know about all the attributes, and repeatedly
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* copying large buffers of vertex data may be very costly) If you add
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* attributes after submitting then you will need to re-call
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* cogl_vertex_buffer_submit to commit the changes to the GPU. (Be carefull
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* to minimize the number of calls to cogl_vertex_buffer_submit though)
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*
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* Note: If you are interleving attributes it is assumed that that each
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* interleaved attribute starts no farther than +- stride bytes from the other
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* attributes it is interleved with. I.e. this is ok:
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* |-0-0-0-0-0-0-0-0-0-0|
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* This is not ok:
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* |- - - - -0-0-0-0-0-0 0 0 0 0|
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* (Though you can have multiple groups of interleved attributes)
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*/
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void
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cogl_vertex_buffer_add (CoglHandle handle,
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const char *attribute_name,
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guint8 n_components,
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GLenum gl_type,
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gboolean normalized,
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guint16 stride,
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const void *pointer);
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/**
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* cogl_vertex_buffer_delete:
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* @handle: A vertex buffer handle
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* @attribute_name: The name of a previously added attribute
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*
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* This function deletes an attribute from a buffer. You will need to
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* call cogl_vertex_buffer_submit to commit this change to the GPU.
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*/
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void
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cogl_vertex_buffer_delete (CoglHandle handle,
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const char *attribute_name);
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/**
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* cogl_vertex_buffer_enable:
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* @handle: A vertex buffer handle
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* @attribute_name: The name of the attribute you want to enable
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*
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* This function enables a previosuly added attribute
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*
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* Since it can be costly to add and remove new attributes to buffers; to make
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* individual buffers more reuseable it is possible to enable and disable
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* attributes before using a buffer for drawing.
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*
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* Note: You don't need to call cogl_vertex_buffer_submit after using this
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* function
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*/
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void
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cogl_vertex_buffer_enable (CoglHandle handle,
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const char *attribute_name);
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/**
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* cogl_vertex_buffer_submit:
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* @handle: A vertex buffer handle
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*
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* This function copies all the user added attributes into buffer objects
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* managed by the OpenGL driver.
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*
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* You should aim to minimize calls to this function.
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*/
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void
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cogl_vertex_buffer_submit (CoglHandle handle);
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/**
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* cogl_vertex_buffer_disable:
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* @handle: A vertex buffer handle
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* @attribute_name: The name of the attribute you want to disable
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*
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* This function disables a previosuly added attribute
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*
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* Since it can be costly to add and remove new attributes to buffers; to make
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* individual buffers more reuseable it is possible to enable and disable
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* attributes before using a buffer for drawing.
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*
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* Note: You don't need to call cogl_vertex_buffer_submit after using this
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* function
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*/
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void
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cogl_vertex_buffer_disable (CoglHandle handle,
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const char *attribute_name);
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/**
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* cogl_vertex_buffer_draw:
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* @handle: A vertex buffer handle
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* @mode: Specifies how the vertices should be interpreted, and should be
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* a valid GL primitive type:
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* <itemizedlist>
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* <listitem>GL_POINTS</listitem>
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* <listitem>GL_LINE_STRIP</listitem>
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* <listitem>GL_LINE_LOOP</listitem>
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* <listitem>GL_LINES</listitem>
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* <listitem>GL_TRIANGLE_STRIP</listitem>
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* <listitem>GL_TRIANGLE_FAN</listitem>
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* <listitem>GL_TRIANGLES</listitem>
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* </itemizedlist>
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* (Note: only types available in GLES are listed)
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* @first: Specifies the index of the first vertex you want to draw with
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* @count: Specifies the number of vertices you want to draw.
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*
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* This function lets you draw geometry using all or a subset of the
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* vertices in a vertex buffer.
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*/
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void
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cogl_vertex_buffer_draw (CoglHandle handle,
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GLenum mode,
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GLint first,
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GLsizei count);
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/**
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* cogl_vertex_buffer_draw_range_elements:
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* @handle: A vertex buffer handle
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* @mode: Specifies how the vertices should be interpreted, and should be
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* a valid GL primitive type:
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* <itemizedlist>
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* <listitem>GL_POINTS</listitem>
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* <listitem>GL_LINE_STRIP</listitem>
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* <listitem>GL_LINE_LOOP</listitem>
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* <listitem>GL_LINES</listitem>
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* <listitem>GL_TRIANGLE_STRIP</listitem>
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* <listitem>GL_TRIANGLE_FAN</listitem>
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* <listitem>GL_TRIANGLES</listitem>
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* </itemizedlist>
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* (Note: only types available in GLES are listed)
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* @min_index: Specifies the minimum vertex index contained in indices
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* @max_index: Specifies the maximum vertex index contained in indices
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* @count: Specifies the number of vertices you want to draw.
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* @indices_typetype: Specifies the data type used for the indices, and must be
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* one of:
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* <itemizedlist>
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* <listitem>GL_UNSIGNED_BYTE</listitem>
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* <listitem>GL_UNSIGNED_SHORT</listitem>
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* <listitem>GL_UNSIGNED_INT</listitem>
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* </itemizedlist>
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* @indices: Specifies the address of your array of indices
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*
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* This function lets you use an array of indices to specify the vertices
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* within your vertex buffer that you want to draw.
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*/
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void
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cogl_vertex_buffer_draw_range_elements (CoglHandle handle,
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GLenum mode,
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GLuint min_index,
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GLuint max_index,
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GLsizei count,
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GLenum indices_type,
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const GLvoid *indices);
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/**
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* cogl_vertex_buffer_ref:
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* @handle: a @CoglHandle.
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*
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* Increment the reference count for a vertex buffer
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*
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* Returns: the @handle.
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*/
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CoglHandle
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cogl_vertex_buffer_ref (CoglHandle handle);
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/**
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* cogl_vertex_buffer_unref:
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* @handle: a @CoglHandle.
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*
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* Decrement the reference count for a vertex buffer
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*/
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void
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cogl_vertex_buffer_unref (CoglHandle handle);
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G_END_DECLS
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#endif /* __COGL_VERTEX_BUFFER_H__ */
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