/* * Cogl * * An object oriented GL/GLES Abstraction/Utility Layer * * Copyright (C) 2010 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, see . * * * * Authors: * Robert Bragg */ #if !defined(__COGL_H_INSIDE__) && !defined(CLUTTER_COMPILATION) #error "Only can be included directly." #endif #ifndef __COGL_ATTRIBUTE_H__ #define __COGL_ATTRIBUTE_H__ #include #include 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__ */