297 lines
7.4 KiB
C++
297 lines
7.4 KiB
C++
/* Freetype GL - A C OpenGL Freetype engine
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*
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* Distributed under the OSI-approved BSD 2-Clause License. See accompanying
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* file `LICENSE` for more details.
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*/
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#ifndef __VERTEX_ATTRIBUTE_H__
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#define __VERTEX_ATTRIBUTE_H__
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include "opengl.h"
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#include "vector.h"
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#ifdef __cplusplus
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namespace ftgl {
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#endif
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/**
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* @file vertex-attribute.h
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* @author Nicolas Rougier (Nicolas.Rougier@inria.fr)
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*
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* @defgroup vertex-attribut Vertex attribute
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*
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* Besides the required vertex position, vertices can have several other
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* numeric attributes. Each is specified in the format string with a letter,
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* the number of components and the data type.
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*
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* Each of the attributes is described in the table below with the set of valid
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* format strings written as a regular expression (for example, "v[234][if]"
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* means "v2f", "v3i", "v4f", etc. are all valid formats).
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*
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* Some attributes have a "recommended" format string, which is the most
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* efficient form for the video driver as it requires less conversion.
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*
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* <table>
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* <tr>
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* <th>Attribute</th>
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* <th>Formats</th>
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* <th>Recommended</th>
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* </tr>
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* <tr>
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* <td>Vertex position</td>
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* <td>"v[234][sifd]"</td>
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* <td>"v[234]f"</td>
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* </tr>
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* <tr>
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* <td> Color </td>
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* <td> "c[34][bBsSiIfd]" </td>
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* <td> "c[34]B" </td>
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* </tr>
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* <tr>
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* <td> Edge flag </td>
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* <td> "e1[bB]" </td>
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* <td> </td>
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* </tr>
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* <tr>
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* <td> Fog coordinate </td>
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* <td> "f[1234][bBsSiIfd]"</td>
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* <td> </td>
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* </tr>
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* <tr>
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* <td> Normal </td>
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* <td> "n3[bsifd]" </td>
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* <td> "n3f" </td>
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* </tr>
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* <tr>
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* <td> Secondary color </td>
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* <td> "s[34][bBsSiIfd]" </td>
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* <td> "s[34]B" </td>
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* </tr>
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* <tr>
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* <td> Texture coordinate </td>
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* <td> "t[234][sifd]" </td>
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* <td> "t[234]f" </td>
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* </tr>
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* <tr>
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* <td> Generic attribute </td>
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* <td> "[0-15]g(n)?[1234][bBsSiIfd]" </td>
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* <td> </td>
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* </tr>
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* </table>
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*
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* The possible data types that can be specified in the format string are described below.
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*
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* <table>
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* <tr>
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* <th> Format </th>
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* <th> Type </th>
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* <th> GL Type </th>
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* </tr>
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* <tr>
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* <td> "b" </td>
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* <td> Signed byte </td>
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* <td> GL_BYTE </td>
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* </tr>
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* <tr>
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* <td> "B" </td>
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* <td> Unsigned byte </td>
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* <td> GL_UNSIGNED_BYTE </td>
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* </tr>
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* <tr>
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* <td> "s" </td>
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* <td> Signed short </td>
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* <td> GL_SHORT </td>
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* </tr>
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* <tr>
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* <td> "S" </td>
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* <td> Unsigned short </td>
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* <td> GL_UNSIGNED_SHORT </td>
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* </tr>
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* <tr>
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* <td> "i" </td>
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* <td> Signed int </td>
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* <td> GL_INT </td>
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* </tr>
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* <tr>
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* <td> "I" </td>
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* <td> Unsigned int </td>
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* <td> GL_UNSIGNED_INT </td>
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* </tr>
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* <tr>
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* <td> "f" </td>
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* <td> Float </td>
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* <td> GL_FLOAT </td>
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* </tr>
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* <tr>
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* <td> "d" </td>
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* <td> Double </td>
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* <td> GL_DOUBLE T </td>
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* </tr>
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* </table>
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*
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* The following attributes are normalised to the range [0, 1]. The value is
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* used as-is if the data type is floating-point. If the data type is byte,
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* short or int, the value is divided by the maximum value representable by
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* that type. For example, unsigned bytes are divided by 255 to get the
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* normalised value.
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*
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* - Color
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* - Secondary color
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* - Generic attributes with the "n" format given.
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*
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* Up to 16 generic attributes can be specified per vertex, and can be used by
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* shader programs for any purpose (they are ignored in the fixed-function
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* pipeline). For the other attributes, consult the OpenGL programming guide
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* for details on their effects.
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*
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* When using the draw and related functions, attribute data is specified
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* alongside the vertex position data. The following example reproduces the two
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* points from the previous page, except that the first point is blue and the
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* second green:
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*
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* It is an error to provide more than one set of data for any attribute, or to
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* mismatch the size of the initial data with the number of vertices specified
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* in the first argument.
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*
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* @{
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*/
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/**
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* Maximum number of attributes per vertex
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*
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* @private
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*/
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#define MAX_VERTEX_ATTRIBUTE 16
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/**
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* Generic vertex attribute.
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*/
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typedef struct vertex_attribute_t
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{
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/**
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* atribute name
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*/
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GLchar * name;
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/**
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* index of the generic vertex attribute to be modified.
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*/
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GLuint index;
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/**
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* Number of components per generic vertex attribute.
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*
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* Must be 1, 2, 3, or 4. The initial value is 4.
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*/
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GLint size;
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/**
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* data type of each component in the array.
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*
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* Symbolic constants GL_BYTE, GL_UNSIGNED_BYTE, GL_SHORT,
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* GL_UNSIGNED_SHORT, GL_INT, GL_UNSIGNED_INT, GL_FLOAT, or GL_DOUBLE are
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* accepted. The initial value is GL_FLOAT.
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*/
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GLenum type;
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/**
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* whether fixed-point data values should be normalized (GL_TRUE) or
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* converted directly as fixed-point values (GL_FALSE) when they are
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* accessed.
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*/
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GLboolean normalized;
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/**
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* byte offset between consecutive generic vertex attributes.
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*
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* If stride is 0, the generic vertex attributes are understood to be
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* tightly packed in the array. The initial value is 0.
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*/
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GLsizei stride;
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/**
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* pointer to the first component of the first attribute element in the
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* array.
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*/
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GLvoid * pointer;
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/**
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* pointer to the function that enable this attribute.
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*/
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void ( * enable )(void *);
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} vertex_attribute_t;
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/**
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* Create an attribute from the given parameters.
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*
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* @param size number of component
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* @param type data type
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* @param normalized Whether fixed-point data values should be normalized
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(GL_TRUE) or converted directly as fixed-point values
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(GL_FALSE) when they are accessed.
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* @param stride byte offset between consecutive attributes.
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* @param pointer pointer to the first component of the first attribute
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* element in the array.
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* @return a new initialized vertex attribute.
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*
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* @private
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*/
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vertex_attribute_t *
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vertex_attribute_new( GLchar * name,
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GLint size,
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GLenum type,
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GLboolean normalized,
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GLsizei stride,
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GLvoid *pointer );
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/**
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* Delete a vertex attribute.
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*
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* @param self a vertex attribute
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*
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*/
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void
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vertex_attribute_delete( vertex_attribute_t * self );
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/**
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* Create an attribute from the given description.
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*
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* @param format Format string specifies the format of a vertex attribute.
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* @return an initialized vertex attribute
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*
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* @private
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*/
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vertex_attribute_t *
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vertex_attribute_parse( char *format );
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/**
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* Enable a vertex attribute.
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*
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* @param attr a vertex attribute
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*
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* @private
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*/
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void
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vertex_attribute_enable( vertex_attribute_t *attr );
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/** @} */
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#ifdef __cplusplus
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}
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}
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#endif
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#endif /* __VERTEX_ATTRIBUTE_H__ */
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